DEER MANAGEMENT AT THE BERNHEIM FOUNDATION PROPERTIES CLERMONT, KENTUCKY
A case study in deer ~anage~ent using electronic infor~ation processing
to ~eet the objectives set by
The Isaac W. Bernhei~ Foundation 536 Starks Bldg. Louisville, KY
By
The Wildlife Society
Copies of this report ~ay be purchased fro~ the publisher
CornerBrook Press Box 106
Copyright (5) 1985 by Aaron N. "oen
No part of this book "ay be reproduced by any "echanical, photographic or electronic process, or in the for" of phonograph recording, nor "ay it be stored in a retrieval syste", trans"itted, or otherwise
copied for public or private use without written per"ission of Aaron N. "oen
Library of Congress Catalog Nu"ber 85-71686
ISBN 0-913523-05-4
i i
Responsibilities Obj ect i ves
GENERAL INFORMATION . The Arboretu~ and Nature Center The Bernhei~ Property . . . . . History ..... Deer populations and ~anage~ent The Agree~ent
STUDY FORMAT Infor~ation collected
Description of area Forage esti~ates
Previous research and cooperators Previous research Cooperators . .
Co~puter processing
Parturition date Deer weights Reproductive characteristics
Range data . . . . . . . . • • . . Plant co~~unity characteristics Forage characteristics ....
Population data . . . . . . . . . . Yearling age class frequencies Sex ratios Esti~ated nu~bers
DEER PARAMETERS Annual weight rhyth~s
Male weight rhyth~s Fe~ale weight rhyth~s
Reproductive characteristics Yearling antler bea~ dia~eters Esti~ated reproductive rates
Metabolic characteristics .....
Base-line ~etabolis~ Multiple of base-line Ecological ~etabolis~ co~position .. Fat content . . Energy reserves
~etabolis~
3 3 5 5 6 8
9 9 9 9
10 10 10 10
15 15 15
· 20 21 21
Forage production Forage production in relation to habitat type Vertical distribution of forage production Digestibility rhyth~s . Ru~en analyses.
POPULATION PARAMETERS Sex and age class frequency distributions
Age-class frequency distributions Sex ratios
Weighted ~eans • . . . . Body weights Ecological ~etabolis~ Forage required . . .
CARRYING CAPACITY AND POPULATION SIMULATIONS Carrying capacity calculations Population si~ulations
MANAGEMENT OPTIONS Do nothing . . Feed the deer Reduce the population
Trapping Hunting .....
ECOLOGICAL CONSIDERATIONS
29 29 29 29 30 30 31
. . 31
47
49
51
INTRODUCTION
White-tailed deer (Odocoileu5 vircinianus), a relatively large (up to 250 pounds, 110 kg) wild herbivore and ru~inant, has beco~e locally abundant in ~any areas of the United States. Ga~e refuges, such as the Bernhei~ Forest, have experienced proble~s with large deer herds because of the lack of hunting or predation as population control ~easures. A deer ~anage~entplan has been requested by the Trustees of the Isaac W. Bernhei~ Foundation for deer population control. This report is a case study using electronic infor~ation processing to provide a deer ~anage~ent plan for the Bernhei~ Foundation properties at Cler~ont, Kentucky.
The Proble~
The deer herd at the Bernhei~ Forest has increased periodically over the years, with reductions by hunting being ~ade when the deer beco~e abundant enough to cause da~age to nearby far~ land. Far~ers with land adjacent to the Forest have been co~plaining about deer da~age in recent yaars, and during the dry su~~er of 1983 ~any deer ~oved fro~ the forested hills to the agricultural lowlands.
Ga~e ani~als, such as deer, are considered a public resource in the United States. Much of the forage that ga~e ani~als consu~e is on private land, however, and this creates proble~s when a specific ~anage~ent goal of private landowners or ~anagers, such as far~ers, orchardists, and park ~anagers, is to ~lnl~lze deer da~age to their crops or lands, while a ~anage~ent goal of wildlife depart~ent5 is to ~axi~ize recreational hunting.
The Bernhei~ Forest has been under contract with the Kentucky Depart~ent
of Fish and Wildlife Resources as a wildlife refuge since 1930, and re~oval of ani~als by public hunting ~ust be agreed to by both the Trustees of the Bernhei~ Foundation and the Kentucky Depart~ent of Fish and Wildlife Resources. Such an agree~ent was reached in 1983, and a herd reduction hunt was held February 3-6, 1984, ad~inistered by the Kentucky Depart~ent of Fish and Wildlife Resources. The Trustees then asked Dr. A.N. Moen to evaluate the carrying capaCity of the Bernhei~ Forest and develop a long ter~ plan for deer ~anage~ent. This report is prepared in fulfill~ent of the consulting agree~ent between The Isaac W. Bernhei~ Foundation, Inc. and the authors to evaluate deer-range relationships on the Bernhei~ Forest and present several ~anage~ent options for consideration.
1
INTRODUCTION .
The Isaac W. Bernhei~ Foundation
was established in 1929 to oversee an Natural Area suitable for wildlife at that ti~e was synony~ous with
ga~e species which had been seriously The Foundation ad~inisters a 225-acre
The Isaac W. Bernhei~ Foundation Arboretu~, a Nature Center, and a conservation. Wildlife conservation increasing populations of the desirable depleted due to uncontrolled hunting. arboretu~ within the 14,500-acre forest.
Responsibilitie§
The Bernhei~ Foundation is responsible for the operation and ~aintenanc~ of the Arboretu~ and Nature Center, and the Bernhei~ Forest. Deer are fenced out of the Arboretu~ and Nature Center. A syste~ of fire trails is ~aintained to protect the 14,500-acre hardwood forest fro~ fire.
Objectives
The current objectives of the foundation are in keeping with those of Isaac W. Bernhei~ who purchased the area to be set aside and ". dedicated to the preservation and enjoy~ent of our natural environ~ent. • (Anony~ous No.1) by the people of Kentucky and their friends. An awareness of plants by the general public is pro~oted by the Arboretu~, and self-guided hiking trails encourage visitors to walk in the woods. School groups can arrange for progra~s with the Foundation's naturalist and horticulturist. Certain areas of the forest are considered ·pri~itive,· with a ~ini~u~ of hu~an
interference. Wildlife is allowed to exist as naturally as possible in the forest, and hunting and trapping are generally not allowed.
Current deer ~anage~ent objectives at the Bernhei~ Forest are to keep the popUlation at a reasonable level, without the ~ajor fluctuations in population size of the past, while investing a ~ini~u~ effort in population control. Since the biology of both ani~al and range should be understood before ~anage~ent decisions to reach these two objectives are ~ade, the objectives of this study are:
Knowledge of the biological characteristIcs of deer and their habitats.
Understanding of the forage and range relationships between deer and different habitats on the forest.
Ability to predict the nu~ber of deer that should be supported by forage resources, and the nu~ber of deer that should be re~oved to keep the population under control.
Insight into the future changes in habitat characteristics and their i~pacts on the carrying capacity of the habitats.
Appreciation of the ~any uses of the Bernhei~ Forest, and the i~pacts, both positive and negative, which deer have on these uses.
2
GENERAL INFORMATION
The BernheiM Forest ArboretuM and Nature Center is located 20 Miles south of Louisville, Kentucky in the "Knobs" of Nelson (5,000 acres) and Bullitt (9,500 acres) counties. The public entrance is near ClerMont on Kentucky Highway 245.
Louisville
Kentucky
Forest
. Knobs Forest
Figure 1. The BernheiM Forest and Knobs Forest, properties of the BernheiM Foundation, are located about 20 Miles south of LouisVille, Kentucky, near ClerMont.
The ArboretuM and Nature Center
The 225-acre arboretuM is located near the public entrance to the Forest (Figure 2). It is surrounded by a 7-foot fence intended to exclude deer froM the area. A sMall lake is considered a barrier, but deer occassionaly SWiM in open water and walk across ice in cold winters to get within the ArboretuM. The ArboretuM has over 1,700 varieties of plants, trees, and shrubs chosen for their hardiness in the Kentucky cliMate and their seasonal interest (AnonYMOUS No.2). There are 15 acres of gardens 5urrounding the ArboretUM Center building and the Nature Center. The latter has several encl06ures with aniMals, including deer and raccoon.
3
3
Area
6
Figure 2. The 14,500-acre Bernhei~ properties include an Arboretu~ and and Nature Center, the Bernhei~ Forest area, the Knobs Forest area, and agricultural botto~londs between the two forest areas. Single-digit nu~bers refer to forage plot locations;
see page 9.
The Bernhei~ Property
The Bernhei~ property is divided into three sections. A 2,000-acre section has been developed for recreational and educational uses, including short hiking paths, picnic areas, and an observation tower. A 7,500-acre section is left in its natural condition, except for fire suppression. The for~er Knobs State Forest is a 5,000-acre section which is separated fro~ the ~ain part of the Forest by the Wilson Creek lowlands. The 2,000- and 7,500-acre sections are referred to collectively as the Bernhei~ Forest area, and the 5,000-acre section is referred to as the Knobs Forest area in this report.
History
The central part of Kentucky was originally covered by an oak-hickory forest. The hills of the Bernhei~ Forest area were cut over by settlers, salt ~akers, and strip ~iners who arrived in the 1700's. The hardwoods provided the high heat needed to boil down brine fro~ salt licks and wells in the area to ~ake salt that was needed by pioneers traveling along the nearby Wilderness Trail. These hardwoods were also used to ~ake charcoal to fuel the open hearth furnaces used to s~elt iron ore. While s~elting in the area declined in the 1830's with the introduction of Besse~er processing, so~e s~elting
occurred during the Civil War as the Confederate States did not have access to iron produced in the north.
Second growth hardwood forest developed on the hills in the last 100 years. So~e selective cutting of white oak occurred on the Knobs State Forest (then known as the South Block) during World War II; there has been no significant a~ount of cutting on any part of the Bernhei~ Forest since then.
The current size of the Forest is 14,500 acres. Isaac W. Bernhei~
bought 13,100 acres in 1929 and created the Arboretu~, Nature Center, Wildlife Refuge, and the Foundation has acquired additional tracts within the forest which had been privately owned since the original purchase in 1929, including the Harrison Fork and Wilson Creek lowlands which were far~ed into the 1970's. So~e hay is still cut in the lowlands owned by the Foundation.
The Knobs Forest area was leased to the Kentucky Depart~ent of Forestry for 50 years for a dollar as a State Forest. The Depart~ent of Forestry subleased the forest to the Fish and 6a~e Co~~ision as a wildlife ~anage~ent
and hunting area. The lease was cancelled in 1980 by ~utual agree~ent of both parties; the Foundation now controls the Knobs Forest area.
A 1930 contract between the Foundation and the Kentucky 6a~e and Fish Co~~ission gave refuge status to the Forest until 1950. The 6a~e and Fish Co~~ission was to stock the land with wild ga~e species, provide the seed and labor for feeding these species for a period of five years, and provide a ga~e warden to patrol the area. The need for a wildlife refuge at that ti~e was great because ~any ani~al populations were very low due to excessive harvesting. The lease was renewed in 1951 for 10 years, and has been renewed at 5-year intervals since 1961, except for the South Block (Knobs Forest area) which has not been part of the refuge contract.
Hunting and trapping was prohibited on the refuge, except for the re~oval of "ver~in" species. The definition of ver~in in the contract included wild
5
GENERAL INFORMATION
cats, gray foxes, weasels, Mink, skunks, jay birds, Cooper's hawk, sharp­ shinned hawk, great horned owl, and all varieties of harMful snakes. No "verMin control" occurs now except in the ArboretuM, where deer are reMoved to avoid daMage to plantings and Muskrats are reMoved to prevent daMage to lake dikes.
Deer Populations and ManageMent
Deer had been extirpated froM the BernheiM Forest area in the early 1900'5. When the BernheiM Forest becaMe a wildlife refuge in 1930, it was stocked with deer, wild turkey, quail, pheasants, and other suitable species of gaMe birds and aniMals. Ten does and five bucks had been received froM Kansas, Missouri, and Texas by DeceMber 9, 1930. Six red deer (Cervus elaphus; elk, or wapiti) were purchased froM the Owensboro Park COMMission in 1930. A total of 54 deer were released in 1930 (Hicks 1939); the ratio of white-tailed deer to red deer released is not known.
FarMs adjacent to the BernheiM Forest were receiving crop daMage frOM deer as early as 1935. Deer began causing probleMs with the developMent of the ArboretuM soon after their release on the Forest. The red deer, because they herded together, caused the Most daMage to the ArboretuM; 45,000 of 60,000 pines planted between 1929 and 1933 were wholly or partly daMaged by deer (Hicks 1939). Hicks states: . Most of the deer daMage is on the estate, but SOMe has occurred on ~urrounding farMS. In general the deer [have] spread. nearly 30 Miles. . [in all directions except north toward Louisville]." Solutions reCOMMended by Hicks included hunting (although it had already failed to pass the state legislature once), trap and transfer, and the use of trained dogs to keep deer out of certain areas. A deer daMage report by Pierle (1942) was siMilar to the one by Hicks (1939).
EstiMates of the population size in 1937 varied frOM 300 to 600 One estiMate suggested that the red deer Made up 75 to 80 percent and tails 20 to 25 percent of the deer population.
deer. white-
SOMe crop daMage claiMS were paid to farMers by the Foundation in the early 1940'5. One farMer sued the Kentucky Fish and GaMe COMMiSSion and the Foundation to recover daMages, and won in the lower court." The Kentucky Court of Appeals overturned the lower court's ruling, absolving the COMMonwealth and the Foundation frOM responsibility for agricultural daMage, and also ruling that farMers could kill deer causing property daMage.
In January of 1946 there was a controlled hunt to reduce the deer herd at the Forest. An eMployee of the Fish and GaMe Division accoMpanied each group of hunters. A second hunt was conducted in DeceMber of 1946. The success of these hunts is not recorded, but J. Lawrence, Chief BernheiM Ranger, believes that success MUSt have geen good because at the tiMe of his eMplOYMent in 1952 there were few deer in the area (personal COMMunication). One SMall herd of 18-20 red deer wintered in the arboretuM area in 1952, and was very destructive.
The deer herd size increased again, so a third hunt was approved by the Fish and Wildlife COMMiSSion in 1957. Hunting occurred on the Forest frOM 1957 to 1960. Many (aSSUMed to be More than 85) deer were taken in 1957, 85 in 1958, 67 in 1959, and only 8 in 1960. These nUMbers were recorded at a
6
GENERAL INFORMATION
check station: successful hunters who left through back entrances of the Forest were not accounted for. Red deer re~ained a proble~ in the Arboretu~: a 7-foot woven wire fence was erected to enclose 400-acres in the Arboretu~ in 1963. The red deer population in the Bernhei~ Forest declined about the ti~e the Arboretu~ fence was erected, due in part to the loss of the concentrated food source the Arboretu~ had provided. There are no red deer on the Forest now. A new fence was put up in 1973, dividing the original fenced area into the central Arboretu~ area and the peripheral picnic grounds.
The deer population increased again to the point where it was causing da~age to area far~s in the 1980's. Biologists for the Kentucky Depart~ent of Fish and Wildlife Resources recognized that the deer population was too high, and that a die-off could occurr. The drought of 1983 accentuated the proble~, resulting in deer co~ing down fro~ the hills to feed on agricultural crops.
The Bernhei~ Forest personnel recognized that there wae a proble~ also. The ~ajor question was how to i~ple~ent a deer population reduction. The Fish and Ga~e Co~~ission wanted the area opened to public hunting, while the Bernhei~ Trustees wanted to use a very li~ited nu~ber of expert hunters. The ~ethod preferred by forest personnel--at night with lights--would have been efficient, but it was controversial. When it beca~e apparent that the Fish and Ga~e Co~~ission would not accept the Bernhei~ Forest proposal, the Trustees voted to allow the Depart~ent of Fish and Wildlife Resources (KDFWR) to ~anage the herd reduction. Per~its for 1,350 hunters were drawn fro~
35,000 applications to hunt at Bernhei~ Forest on February 3-6, 1984.
The general pattern of the deer population fluctuations since 1930 is shown in Figure 3. Periodic large-scale reductions in population size have been followed by 10-to-20 year periods when no atte~pts have been ~ade to control population size. Now, a ~anage~ent plan is desired by the Bernhei~
Foundation which will result not only in ~aintenance of a ~ore constant population size but also one which is s~all enough to cause little or no da~age to the natural vegetation and adjoining croplands.
Figure 3.
+
+
+
+
+
+----+----+----+----+----+----+----+----+----+----+----+----+ 1930 1940 1950 1960 1970 1980
Periods of increasing population size and large-scale herd reductions have alternated every few years as a result of deer ~anage~ent policies at the Bernhei~ Forest since 1930.
7
GENERAL INFORMATION
The AgreeMent
This report is the result of an AGREEMENT drawn up by The Isaac W. BernheiM Foundation and Dr. A.N. Moen to evaluate deer ManageMent options at the BernheiM Forest ArboretuM and Nature Center. Two Main considerations in the AgreeMent were evaluations of deer biology and population characteristics, and land use characteristics.
The AgreeMent also included requests to deterMine optiMUM deer populations based upon different levels of habitat deterioration, and identify ManageMent options which are available to achieve the recoMMended deer population, with each option assessed froM the standpoint of effectiveness, hUMane treatMent of the aniMal, costs, etc.
8
STUDY FORMAT
This report is based on co~puter-proces~ed infor~ation about the deer and the habitats on the Bernhei~ and Knobs Fore~t areas. It is pri~arily an analysis of carrying capacity; habitat characteristics were evaluated with field work conducted by R.A. Moen and carrying capacity analyzed with equation~ relating forage production to deer require~ents and population characteristics that have been derived by A.N. Moen.
Infor~ation Collected
Infor~ation about the area, the habitats, forage quantities and qualities, and the deer has been collected froM field work, previously published reports, BernheiM files, and the Kentucky DepartMent of Fish and Wildlife Resources.
Description Qf ~
The Bernhei~ properties are covered with upland forest, co~posed ~ainly of oaks and hickory, and ~esic valley forest, co~posed of beech, ~aple, and tulip poplars (Medley 1984). Virginia Pine and Eastern Red Cedar are locally abundant. There are 14,000 acres in hardwood forest, 225 acres in the Arboretu~, and 150 acres in cleared lowlands. Hay is harvested fro~ half of the cleared lowlands; the other half is ~owed on a three-to-five year rotation to prevent shrub invasion. Roads, fire trails, and openings in the forest cover appoxi~ately 125 acres.
Forace esti~ates
The a~ount of forage present ha~ been esti~ated with a procedure developed by A.N. Moen and C.W. Severinghaus (~s in preparation). Stand characteristics were entered on a standard forage evaluation for~ sheet at plots in the following locations (See Figure 2):
3 sets of 4 plots each, with plots located at the botto~,
1/3 up, 2/3 up, and at the top of the slope, on north, south, east and west exposures in the Bernhei~ Forest area. These plots were located in the Guerilla Hollow area (1), the Poplar Level area (2), and the hills above the Harrison Fork area near the county road (3). Locations 1, 2, and 3 are ~arked in Figure 2.
3 sets of 4 plots each, with plots located at the 1/3 uP. 2/3 uP. and at the top of the ~lope, on south, east and west exposures in the Knobs Forest Locations 4, 5, and 6 are ~arked in Figure 2.
12 plots within the exclosure areas.
botto~,
north, area.
4 plots in pine plantation on top of Knobs Forest plateau (Location 7 in Figure 2).
9
STUDY FORMAT
4 plots on the North facing slope which overlooks Wilson Creek valley (Location 8 in Figure 2).
4 plots on a very bare wooded slope above the Wilson Creek botto~lands (Location 9 in Figure 2).
5 plots in the open lands not cropped for hay (Location 10 in Figure 2).
Plots were not set up on fields being cropped for hay, but the stubble was ~easured to esti~ate the aMount of plant ~aterial present. Results of forage plot analyses are given in pounds of forage available per acre. Results frOM the 48 plot sets were analysed using one-way analysis of variance to test for differences between slopes and elevations; no significant differences were observed. Results fro~ the Bernhei~ Forest area and the Knobs Forest area plots were cOMpared using Student's t-test; a significant difference (0.05 level) in forage production between the two areas was observed. Forage production was calculated separately for the BernheiM and Knobs Forest areas, the Meadowland, and the hayland. Total forage production was calculated by ~ultiplying pounds per acre by the acreage of each area.
Previous Research and Cooperators
The white-tailed deer is probably the best-studied wildlife species. Over 6,000 scientific publications on whitetails are listed in the 7-Part series on The Biology and Manage~ent of Wild Ru~inants (Moen 1980-1982). These publications are found in over 1,000 different serials and books.
Previous Research
Previous research by biologists has contributed large aMounts of data on white-tailed deer to the database currently used by Dr. Moen at Cornell University. Support for the long-terM research progra~ has been provided by Many funding agencies through the College of Agriculture and Life Sciences at Cornell, and is gratefully acknowledged.
Cooperators
Personnel at the BernheiM Forest, particularly C.K. McClure and J. Lawrence, have been Most helpful in providing needed inforMation. The cooperation of J. Phillips and W. Graves of the Kentucky DepartMent of Fish and Wildlife Resources is gratefully acknowledged.
COMputer Processing
The inforMation collected during the field work and froM previous research has been used in cOMputer-based inforMation processing for analyses of deer weights, reproductive rates, nutritional status, and population dynaMics. The inforMation ~ay be updated annually, providing the Most current analysis of aniMal-range relationships possible. Such an approach Makes it possible to evaluate the effectiveness of decisions Made in relation to objectives set.
10
THE BIOLOGICAL FRAMEWORK
AniMal and environMent forM an inseparable pair, and it is iMperaiive that both aniMal requireMents and range resources be evaluated together if carrying capacity is to be evaluated properly (Moen 1973). Using algorithMs that have been derived frOM research on white~tailed deer by Many researchers over the years, liMited aMounts of data May be used to generate overall representations of aniMal-range relationships. For exaMple, energy MetabolisM rhythMs over
. the annual cycle May be calculated as a function of tiMe of year and reproductive status (Moen 1978). The calculation of energy requireMents is related to energy available on the range when evaluating carrying capacity. Deer data, range data, and population data are SUMMarized below.
Deer Data
T~ree iteMS of deer data are needed when calculating their energy requireMents over the annual cycle, including the Mean parturition date, weights over the annual cycle, and reproductive characteristics of different age classes. These data are used to calculate Metabolic rates, body COMpOSition, and forage requireMents.
Parturition date
The Mean parturition date for deer in the BernheiM Forest area May be estiMated as May 31 (JDAY 151). This date is used when deterMining the age in days (AGDA) of deer in different age classes. For exaMple, a fawn-of-the-year is 167 days old on NoveMber 15 (JDAY 319), deterMined by subtracting 152 frOM 319, and older deer are 365 days older in each successive age class.
~ weights
The annual weight cycle of deer in different age classes has been deterMined using the procedures described in Moen and Severinghaus (1981). The deer weights available for the BernheiM Forest frOM the 1984 herd reduction indicated that the yearling deer weigh about 85 percent as Much as deer in the Adirondack region of New York State, corrected for the tiMe of year when weights were taken. A Sinusoidal weight curve for deer in the B~rnheiM area was generated by applying a Multiplication factor of 0.85 to the Adirondack deer weight curve.
Reproductive characteristics
Reproductive rates are related to body weights at breeding; larger feMales have a higher conception rate. Further, the average antler beaM diaMeter of the Male yearling age class is a good predictor of the reproductive rates of fawns, yearlings, and adults (Severinghaus and Moen 1983).
11
Range Data
Deer condition is directly related to the overall condition of the range. Forage relationships are particularly iMportarit because productivity is directly related to the availability of nutrients. Thus plant cOMMunity and forage characteristics are used to describe the range and estiMate the forage energy available to the deer population throughout the year.
Plant COMMunity Characteristics
Plant cOMMunity characteristics affect forage production by affecting growing conditions in the understory. The stage in succession is particularly iMportant. High forage production occurs in the early stages in succession when plants are invading and an overhead canopy has not yet developed, and low forage production occurs when the canopy is well-developed and dense, allowing little light to penetrate to the understory.
The age of a tiMber stand May be used to estiMate the aMount of forage available. Herbaceous plants (except during winter) and shrubs provide a large part of the forage available during the regeneration stage. Tree seedlings are becoMing established, and MaxiMUM forage production at heights to which deer can reach occurs 5-20 years after regeneration begins. In the sapling stage, with trees having a diaMeter at breast height (OBH) of 1 to 4 inches, the light at ground level is diMinished due to the developing canopy, and ground-level forage production is decreased. An increasing proportion of plant tissue production is occurring above heights to which deer can reach. Most plant tissue production occurs in the canopy above the deer when trees are in the poletiMber stage, with a DBH of 4 to 9 inches, and the sawtiMber stage, with Mature trees having a DBH )9 inches.
Forage characteristics
Two Main forage characteristics--quantity and quality--are conSidered when evaluating the nUMber of deer that can be supported on the range. Forage production and forage COMposition and digestibility are discussed below.
Forage Production. Forage production May be estiMated directly with on­ site evaluations using rapid nondestructive visual procedures described in a Manuscript in preparation by C.W. Severinghaus and A.N. Moen, or indirectly by relating forage production to plant COMMunity and tiMber stand characteristics. Equations and COMputer algorithMs will be described in the previouslY-Mentioned MS in preparation. The general pattern of forage production in relation to tiMber age classes is illustrated in Figure 4.
Forage COMposition. Major tree species present include oaks, beeches, Maples, hickories, and tulip poplar. Eastern Red Cedar and Virginia Pine are locally abundant. Major understory species are greenbrier and grasses.
Forage diaestibilities. Forage digestibilities through the year are iMportant considerations when deterMining the aMount of forage required to support a population. The nUMber of species conSUMed and variability in plant parts taken throughout the year Makes accurate MeasureMents of species
12
THE BIOLOGICAL FRAMEWORK
digestibilities difficult and tiMe-consuMing. Analyses of deer diets and cell cOMposition provide enough inforMation to derive a general pattern of diet digestibility throughout the year, however.
READ Y-AXIS AS AMOUNT PER ACRE +
+
+
+
+
+----+----+----+----+----+----+----+----+----+----+ o 5 10 15 20 25 30 35 40 45 50+
YEARS
Figure 4. The general pattern of forage production in relation to age of the tiMber stand. MaxiMuM production May reach several hundred pounds.
Population Data
Four key population data are needed for the algorithMs used to predict populations. They are: yearling age clas~ frequencies, sex ratio of fawns, sex ratio of yearlings and adults, and estiMated nUMber of deer.
Yearling age-class frequencies
Yearling age class frequencies of both Males and feMales are used to estiMate age-class population structure froM year class 1 to 12. The age-class frequency of yearling Males is estiMated froM a general knowledge of herd history, and the age class frequency of yearling feMales is calculated froM the reproductive rates of feMales. Frequencies of age classes two years and older are calculated with an exponential algorithM.
~ ratios
~ B&i1Q of~. The sex ratio of fawns at birth is an iMportant paraMeter when predicting population dynaMics as it is a partial deterMinant of the nUMber of reprodUCing feMales in a population. It is predicted froM yearling antler beaM diaMeter, an indicator of deer productivity.
~ Ratios Qf YearlinQs AnQ Adults. The sex ratio of the yearling and adult portion of the population is an essential paraMeter for predicting population dynaMics. It is iMpossible to Measure directly, however. The ratiO depends on the history of the population. Deer populations which are
13
THE BIOLOGICAL FRAMEWORK
hunted have relatively fewer ~ales than those which are not hunted.
Esti~ated nu~bers
The esti~ated nu~ber of deer in a population is used at the start co~puter-based analyses, followed by co~parisons of new esti~ates and with the nu~bers predicted by population analyses fro~ year to year.
14
DEER PARAMETERS
The deer para~eters discussed below are used in the calculations of carrying capacity as energy require~ents are deter~ined and related to the energy resources on the range.
Annual Weight Rhyth~s
Annual weight rhyth~s provide infor~ation on increases and decreases in body weights through the year as deer accu~ulate fat during the su~~er when forage resources are More abundant, and Mobilize fat during the winter when forage resources becoMe less abundant. This is part of an overall energy conservation strategy (Moen 1976) characteristic of deer in northern states.
~ weight rhythMs
Annual weight rhythMs of Male deer are calculated with a sine wave algorith~
that fluctuates between ~axiMU~ and MiniMUM weights through the year (Moen and Severinghaus 1981).
MaximUM ~ weights. MaxiMuM live weights of Male deer on the BernheiM Forest May be calculated with the follOWing equation:
where 2.81 0.45256
MXMK = 2.81*AGDA A 0.45256,
AXFK = a-value for MaxiMUM Male weight in kg, BXFK = b-value for MaxiMUM Male weight in kg, and age in days on the JDAY of MaxiMUM weight.
Calculated MaxiMUM Male weights in kg and pounds on October 28 (JDAY 301) are given in Table 1.
Table 1. Calculated MaxiMU~ weights of Males in age classes 0 to 5, in kg (MXMK) and pounds (MXMP).
AGCl AGDA MXMK MXMP
0.5 150 27 60 1.5 515 47 104 2.5 880 60 133 3.5 1245 71 155 4.5 1610 79 174 5.5 1975 87 191
MiniMUM ~ weicht;. MiniMUM Male weights, reached on April 16 (JDAY 106) have been calculated with the equation:
15
DEER PARAMETERS
Calculated ~ini~u~ ~ale weights in kg and pounds are given in Table 2.
Table 2. Calculated ~ini~UM weights of ~ales in age classes 0-5, in kg (MNMK) and pounds (MNMP).
AGCl AGDA ~ MNMP
YCl0 320 20 45 YCLl 685 31 68 YCL2 1050 39 85 YCl3 1415 46 101 YCl4 1780 52 114 YCl5 2145 57 126
Annual weicht cycles. The annual weight cycle of Males is calculated with an aSYMMetric sine wave equation (Moen and Severinghaus 1981) which includes the ~axi~UM and ~iniMU~ weight equations given above and the priMary and secondary phase corrections. Phase corrections were deterMined within the co~puter progra~ fro~ the inputs for JDAY of Maxi~u~ Male weight (JXMW = 301) and JDAY of ~iniMU~ ~ale weight (JNMW - 106). Calculated ~ale weights are plotted in Figure 5.
KG KG lBS
100-+ +-100 220
80-+ +- 80 176
0-+-+----+----+----+----+----+----+----+----+----+----+----+-+-0 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
Figure 5. Annual rhythMS in Male deer weights.
16
Fe~ale weight rhyth~s
Annual weight rhyth~s of fe~ale deer are calculated with a sine wave algorith~ that fluctuates between ~axi~u~ and ~ini~u~ weights through the year (Moen and Severinghaus 1981).
MaxiMu~ ~ weights. The relationship between AGDA and ~axi~u~ fe~ale
weight 1n kg ~ay be represented with the following regression equation in which AGDA is the independent variable and MXFK (~axi~u~fe~ale weight 1n kg) is the dependent variable. The equation is:
MXFK~9.2938*LN(AGDA)-19.5;
where 9.2938 AXFK = a-value for ~axi~u~ fe~ale weight in kg, -19.5 BXFK b-value for ~axi~u~ fe~ale weight in kg, and
AGDA age in days on the JDAY of ~axi~u~ weight.
Maxi~u~ weight of fe~ales is reached on October 28 (JDAY 301) . Calculated ~axi~u~ fe~ale weights in kg and pounds are given in Table 3.
Table 3. Calculated ~axi~u~ weights of fe~ales in age classes 0-5, in kg (MXFK) and pound5 (MXFP).
~ AGDA !1XEK t1Xff
YCL0 150 27 59 YCLl 515 38 85 YCL2 880 43 96 YCL3 1245 47 103 YCL4 1610 49 108 YCL5 1975 51 112
Mini~u~ live weiahts. Mini~u~ weights through the annual cycle are esti~ated to be about 85% of ~axi~u~ weights, reached on MAY l(JDAY 121). Mini~u~ fe~ale weights in kg (MNWK) are calculated with the equation:
MNFK=7.60455*LOG(AGDA)-22.76,
where -22.76 ANFK = a-value for ~ini~u~ fe~ale weight in kg, 7.60455 BNFK = b-value for ~ini~u~ fe~ale weight in kg, and
AGDA = age in days on the JDAY of ~ini~u~ weight.
Mini~u~ weights of fe~ales are given in Table 4.
17
DEER PARAMETERS
Table 4. Calculated I'Ilnll'lUM weights of fel'lales in age classes 0-5, in kg (MNFK) and pounds (MNFP).
AGCl AGDA MNFK MNFP
YCl0 335 21 47 YCLl 700 27 59 YCl2 1065 30 67 YCl3 1430 32 71 YCl4 1795 34 75 YCl5 2160 36 78
Annual weight cycles. The annual weight cycle of feMale6 is calculated with an a6YMMetric sine wave equation (Moen and Severinghau5 1981) which includes the Maxil'lul'I and l'Iinil'lUM weight equations given above and the priMary and secondary phase corrections. Phase corrections are deterMined within the cOMputer progral'l frol'l the inputs for JOAY of l'IaxiMuM feMale weight (JXFW = 301) and JOAY of l'Iinil'lul'I fel'lale weight (JNFW = 121). Fel'lale weights through the annual cycle are plotted in Figure 6.
KG KG lBS
100-+ +-100 220
90-+ +- 90 198
80-+ +- 80 176
70-+ +- 70 154
Figure 6. Annual rhythl'ls in fel'lale deer weights.
18
DEER PARAMETERS
Reproductive Characteristics
Reproductive rates and sex ratios are funda~ental reproductive para~eters
that ~ust be known or esti~ated when ~aking population predictions. Values used for the Bernhei~ Forest are discussed below.
Yearling antler bea~ dia~eters
Yearling antler bea~ dia~eters are good predictors of reproductive rates of fe~ale white-tailed deer (Severinghaus and Moen 1983). This correlation exists because ~ales and fe~ales coexist on the sa~e range, and antler growth, ~easured by the bea~ dia~eter about two c~ above the base, reflects range conditions which also affect the productivity of the fe~ales. Larger antler bea~ dia~eters and higher body weights are characteristic of deer on good range, and s~aller antler bea~ dia~eters and lower body weights are characteristic of deer on poor range.
Esti~ated reoroductive rates
The reproductive rates of fe~ales bred as fawns (FARR), yearlings (YERR), adults (ADRR), and older adults (OARR) May be predicted with the following equations (Severinghaus and Moen 1983), where YABD is the independent variable:
FARR=0.078*YABD-1.135, YERR=0.151*YABD-1.344, ADRR=0.072*YABD+0.463, and OARR=0.111*YABD-0.455.
The ~easured YABD of deer with low weights, such as those on the Bernhei~
Forest is expected to be between 12 and 15 ~M; the Measured YABO is corrected to account for ~easure~ent bias to calculate the reproductive rates. Corrected YABD and calculated reproductive rates based on these YABD are given in Table 5.
Table 5. Calculated reproductive rates of fawns, yearling, and adult does in relation to average ~ale yearling antler bea~ dia~eter in ~~.
YABD 12.0M~ 13.5~M 15.0M~
eYBD 10.1~M 12.0~M 14.2~~
FARR 0.00 0.00 0.04 YERR 0.18 0.46 0.92 ADRR 1.19 1.32 1.54 OARR 0.66 0.87 1.12
19
DEER PARAMETERS
Metabolic Characteristics
Metabolic characteristics May be calculated through the annual cycle and the energy cost of living and forage required to Meet this cost estiMated. Three paraMeters, base-line MetaboliSM per day, Multiple of base-line MetaboliSM, and ecological MetaboliSM per day, are used to estiMate the Metabolic rate, using the equations discussed in Moen (1978, 1981, 1983).
Base-line MetaboliSM
Base-line MetaboliSM per day (BlMO) is calculated with the following forMula:
where 70 IFWK
a MatheMatical constant, and ingesta-free weight in kg.
Ingesta-free weight in kg (IFWK), used when calculating MetaboliSM and body COMpOSition, is estiMated with the follOWing forMula, SiMplified frOM Robbins et a1. (1974):
where ClWK calculated live weight in kg.
Multiple of base-line MetaboliSM
The Multiple of base-line MetaboliSM through the annual cycle May be calculated with a sine wave forMula in Moen (1978), where:
MBlM = f(tiMe of year and nUMber of fawns).
A late fall-to-early spring average MBlM of 1.B May be used for both Males and feMales, since they are siMilar during that tiMe. In late spring feMales experience rlslng energy costs of gestation, especially in the last third of gestation, followed by an additional cost for lactation during the SUMMer.
EcoloQical MetaboliSM
Ecological MetaboliSM short forM:
MetaboliSM per day is deterMined by Multiplying by the Multiple of base-line MetaboliSM for the given
ElMO=BlMO*MBlM.
base-line JOAY. In
The equations for BlMO and MBlM are COMbined into a final overall equation for ELMO in the COMputer prograM which is used to calculate the daily energy cost of living for a free-ranging aniMal.
20
DEER PARAMETERS
Body COPlposition
The weight changes through the year reflect changing fractions of fat and water. Protein and ash contents rePlain fairly constant at about 20% and 3%, respectively. As weights increase, fat fractions increase and water fractions decrease (Robbins et al. 1974). These cOPlposition changes through the year result in changes in energy reserves available during tiPles of Pletabolic stress, such as late winter.
Ell content
The equation used to calculate the fat content in kg (FATK) of white-tailed deer as a function of ingesta-free weight in kg is (Plodified froPl Moen 1980):
FATK=e A (2.1345.(10g IFWK)-6.3944).
The fat contents and fat fractions of both Plales and fePlales at peak weights are given in Table 6. The percent of ingesta~free weight represented by fat is illustrated in Figure 7.
Eneray reserves
The fat content of the body represents an energy reserve which is Plobilized when daily intake is not sufficient to Pleet the daily energy cost of living. The fat contents given above Play be used to estiPlate the potential fat contribution to the Pletabolic requirePlents when the deer go froPl PlaxiPluPl to PllnlPlUPl weight. The caloric contribution of the fat to the Pletabolic requirePlents and the fraction of the Pletabolic requirePlents represented by the fat are given in Table 7. The contribution of the fat reserve to the average daily Pletabolic requirePlent is illustrated in Figure 8.
Table 6. Fat contents and fat fractions of Plale and fePlale deer at peak weights.
AGCL MXWK IFWK Eftlli. FATP
YCL0 MALE 28 25 1.7 6.6 FMLE 28 25 1.7 6.6
YCLl MALE 46 41 4.7 11.4 FMLE 38 34 3.2 9.3
YCL2 MALE 60 56 8.8 15.7 FMLE 43 39 4.2 10.8
YCL3 MALE 69 62 10.8 17.4 FMLE 47 42 4.9 11.7
YCL4 MALE 78 70 13.8 19.7 FMLE 49 44 5.4 12.3
YCL5 MALE 86 77 16.6 21.6 FMLE 51 46 5.9 12.8
21
25 + - = Males + 25 --- ... Fel"lales I
20 + + 20
15 + + 15
I I
4.5 5.5
Figure 7. Fat content of deer at peak weights, expressed as percent of ingesta-free weight, in relation to age in years. (Data frol"l Table 6>'
Table 7. Maxil"lul"I and I"Ilnll"lUI"I weights of deer, fat contents, and fat characteristics in relation to average daily l"Ietabolic rate frol"l late fall to early spring.
5
o
MDPT EBI CHBBBQT~BISIIC~ AGCl MXIK FTKX MNIK FTKN IFWK ELMO KG KCAl PCNT
YClO MALE 25 1.7 18 0.8 21.5 1260 0.9 48 3.8 FMlE 25 1.7 18 0.8 21.5 1260 0.9 48 3.8
YCLl MALE 41 4.7 28 2.1 34.5 1790 2.6 138 7.7 FMlE 34 3.2 23 1.4 28.5 1550 2.8 148 9.5
YCl2 MALE 56 8.8 34 3.2 45.0 2190 5.6 296 13.5 FMlE 39 4.2 27 1.9 33.0 1740 2.3 122 7.0
YCl3 MALE 62 10.8 41 4.7 51.5 2420 6.1 323 13.3 FMlE 42 4.9 29 2.3 35.5 1830 2.6 138 7.5
YCl4 MALE 70 13.8 46 5.9 58.0 2650 7.9 418 15.8 FMlE 44 5.4 31 2.6 37.5 1910 2.8 1:'8 7.8
YCl5 MALE 77 16.6 51 7.3 64.0 2850 9.32 492 17.2 FMlE 46 5.9 32 2.8 39.0 1970 3.1 164 8.3
DEFINITIONS OF TABLE HEADINGS: AGCl = Age class MXIK = Maxil"lul"I ingesta-free weight FTKX Fat content in kg at l"Iaxil"lul"I weight MNIK = Minil"lul"I ingesta-free weight FTKN Fat content in kg at I"Ilnll"lUI"I weight
MDPT IFWK Midpoint ingesta-free weight in kg ELMO = Ecological l"Ietabolisl"l per day
KG = Kilogral"ls KCAl Kilocalories contribution of fat l"Iobilized to ELMO PCNT = Percent contribution of fat l"Iobilized to ELMO
22
30 +
DEER PARAMETERS
• + 5 1
+._--+ 0 5.5
Figure B. Contribution of the fat reserves to the average daily I'Ietabolic requirel'lent of deer of different ages in the winter. (Data frol'l Table 7).
Note that the fat reserve contributes about 4% to 10% of the energy required daily by I'Iale and fel'lale deer 0.5 and 1.5 years old, and by fel'lale deer to 5.5 years old. The younger deer are I'Iore dependent on forage since their fat reserves are sl'laller than those of older deer. Yet older deer have the advantage when foraging; physically they are larger and behaViorally they are dOl'linant.
23
RANGE PARAMETERS
Range para~eters used to esti~ate the resources available to the deer include woodland and openland habitat characteristics, forage production relation to habitat characteristics, and digestibilities of herbaceous woody plant ~aterial through the annual cycle.
Habitat Types
herd in
and
Habitat characteristics, including local forest type, age of the stand, and canopy density ~ay be used to ~ake esti~ates of forage production with procedures described in a deer ~anage~ent ~anual in preparation by A.N. Moen and C.W. Severinghaus. Field work is then co~pleted in order to co~pare the predictions based on habitat characteristics with on-site production esti~ates. Habitats on the Bernhei~ Forest ~ay be divided into the hardwood forest, which covers ~ost of the area, and the cleared botto~5. The Bernhei~ Forest area, the Knobs Forest area, and the cleared lowlands have been evaluated separately for esti~ates of forage production. Results of these ~easure~ents are discussed below.
Upland habitats
.A ~ature hardwood forest covers 97% (14,000 of 14,500 acres) of the Bernhei~
properties. Hardwood species are pri~arily oak, hickory, beech, and ~aple with so~e basswood, tulip poplar and syca~ore also present. Two conifers, Eastern Red Cedar and Virginia Pine, are locally abundant. The understory has so~e regeneration occurring, but the thick canopy coverage li~its the a~ount of regeneration which can take place. Except for parts of the Knobs Forest area which were logged during World War II, the forest trees are 80-100 years old. Forage evaluation plots showed that slightly ~ore forage is available in the Knobs Forest area than in the Bernhei~ Forest area.
Lowland habitats
The 150 acres of open lowland is divided into approxi~ately 75 acres of alfalfa and clover that is cropped for hay, and 75 acres which are ~owed every 3 to 5 years to prevent shrub invasion.
Forage Production
Forage supplies the nutrients, including energy, which ~eet the daily require~ents for ~aintenance and productivity. Forage production has been deter~ined in the following way.
Forace production in relation 1£ habitat ~
Visual esti~ates of stand characteristics were ~ade in 121 plots UNIVERSAL KEY (Moen and Severinghaus In Press) and the Forage
25
RANGE PARAMETERS
Worksheet. The a~ount of forage alotted to deer was calculated with a BASIC progra~ using a Radio Shack Model ·100 portable co~puter. Results are su~~arized in Table 8.
Table 8. Average field-esti~ated dry-weight woody forage production allocated to deer in different habitats on the Bernhei~ area at 0.2 allowed.
Habitat Production. pounds/acre I2ial production
WOODLAND
Meadows Haylands
7.7 13.6
15.0 10.0*
9000 5000
75 75
69300 68000
1125 750
* 6" stubble after last cutting of hay; little new growth available to deer
Vertical distribution Qf forage production
Forage production in four 20-inch layers was esti~ated at each forage plot. An overbrowsed range would have a low fraction of forage production within reach of deer, and a large fraction above the height to which deer can reach. This results in a "browse line." Average values for the 48 plots taken in the Bernhei~ Forest area and the Knobs Forest area are illustrated in Figure 9.
60"-80"
40"-60"
20"-40"
0"-20"
+
+
+
+ +----+----+----+----+----+----+----+----+----+----+ o 10 20 30 40 0 10 20 30 40 50
PERCENT OF FORAGE IN EACH LAYER
Figure 9. Average percents of forage in each 20" layer in the Bernhei~ and Knobs areas.
26
RANGE PARAMETERS
Digestibility rhythMs
Digestibilities of forages are Measured with 1n vitro digestion techniques and in vivo digestibilities are predicted as a function of the percent acid detergent fiber (PADF) in the forage. Since forage digestibility is priMarily a function of plant cell structure, the digestible energy coefficients of different plants follow their phenology through the growing season. The percent acid detergent fiber over the annual cycle shown in Figure 10 is derived froM unpublished data of A.N. Moen. This pattern May be converted to a pattern of predicted digestibility (Figure 11) with the following equ~tion:
1.0 + I
+ 0.9
+ 0.8
+ 0.7
+ 0.6
+ 0.5
+ 0.4
+ 0.3
+ 0.2
+ 0.1
0.0 +--+----+----+----+----+----+----+----+----+----+----+----+--+ 0.0 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
Figure 10. General pattern of percent acid detergent fiber froM unpublished data.
RUMen analyses
The rUMen contents of a road-killed deer was collected and analyzed for percent acid detergent fiber. The herbaceous content of the rUMen yielded a PADF of 39X, which is converted to about 67X digestibility. This deer was killed near the public entrance to the BernheiM Forest; it had been foraging on roadside grasses and other herbaceous plants.
27
+ 90
+ 80
+ 70
+ 60
----______ ~+ 50
+ 40
+ 30
+ 20
+ 10
o +--+----+----+----+----+~---+----+----+----+----+----+----+--+ 0 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
Figure 11. General pattern of forage digestibility based on percent acid detergent fiber.
28
POPULATION PARAMETERS
The nu~ber of deer on the Bernhei~ and Knobs Forest areas cannot be ~easured
directly. A proportionality-based deer population progra~, designed by A.N. Moen, per~its one to set up an initial population with a ~ini~u~ of infor~ation. Initial deer population para~eters and nu~ber esti~ates have been ~ade based on the results of the e~ergency hunt in February, 1984.
Sex and Age-Class Frequency Distributions
Sex and age-class frequency distributions are used when calculating weighted ~ean values for bio~ass, ecological ~etabolis~, and forage require~ents to deter~ine the carrying capacity of an area. The results are then weighted according to the fractions of ~ales and fe~ales in each of the age classes.
Age-class frequency distributions
~ age-class frequency distributions. EstiMates of the percents of ~ales in six age classes are listed below, calculated with a successive­ Multipication equation in the co~puter progra~ for calculating an exponential pattern of age class frequencies based on fractions of yearling ~ales in the population (0.40) at the beginning of winter as the inputs.
FRCT 0.40 0.24 0.14 0.09 0.05 0.8
FeMale age-class frequency distributions. FeMale age class frequencies are calculated frOM the yearling antler beaM dia~eter (YABD), which is a predictor of reproductive rates and hence potential recruit~ent of fe~ales.
Esti~ates of the percents of fe~ales in six age classes are listed below, based on a yearling antler beaM dia~eter of 13.5 MM.
AGCl Y.Q.bJ. YCl2 ~ .Y.lli m..s .Y.k!...§..±
FRCT 0.27 0.20 0.14 0.11 0.08 0.21
lli ratios
Sex ~ Qf fawns. The ~ale to fe~ale fawn sex ratio (MFFR) is estiMated as a function of yearling antler bea~ dia~eter with the equation:
where YABD ratiO, based fe~ales.
MFFR = 82.8683*YABD~0.09665
Mean yearling antler bea~ dia~eter in ~~. The on an uncorrected YABD of 13.5 ~~, is 105.3
predicted ~ales per
sex 100
~ ratios of ih§ pre-Winter population. The feMale-to-~ale population ratio was deterMined fro~ the population evaluations of the deer on the Bernhei~ Forest. Males Made up 53% and fe~ales 47% of the pre-winter population in 1984, after the eMergency hunt.
29
POPULATION PARAMETERS
Weighted Means
Esti~ates of biological characteristics using weighted ~eans which consider the frequency of each of the sex and age classes in the population (Moen 1981) are used to ~ake accurate esti~ates of population para~eters. The weighted ~ean population characteristics discussed below are based on the sex and age-class frequencies discussed in the previous section. Current-year reproduction was added using the reproductive rates calculated with a yearling antler bea~ dia~eter of 13.5 ~~ (see Table 5, page 19). Fawn survival rates fro~ parturition to the beginning of winter were esti~ated to be about 0.80 and 0.75 for ~ales and fe~ales, respectively.
~ weights
Weights of ~ales and fe~ales in each age class fro~ ~axi~u~ to ~ini~u~ through the winter were used to deter~ine a ~idpoint winter weight which was used to derive the weighted ~ean bio~ass of the population. The ~idpoint weight of each age class was ~ultiplied by the fraction of the ~ale or fe~ale population. in that ag~ class and the products su~~ed. Finally, ~ale and fe~ale fractions of 0.53 and 0.47 were ~ultiplied by the weights for each sex. These data are su~~arized in Table 9.
Table 9. Data used in deter~ining the weighted ~ean weight of the deer at the Bernhei~ Forest.
MALE YCL0 YCLl Yru ~ ~ Y.klli
MXWK 28 46 60 69 78 B6 MNWK 20 31 38 45 51 57 MOPT 24 38 49 57 65 72
FRAC 0.21 0.29 0.20 0.12 0.07 0.11 WMWT 5.0 11.0 9.8 6.8 4.6 7.9 45 KG
FEML ~ yell ~ YCL3 YCL4 YC.lli
MXWK 27 38 43 47 49 51 MNWK 20 26 30 32 34 35 MOPT 24 32 36 40 42 43
FRAC 0.21 0.22 0.16 0.12 0.08 0.21 WMWT 5.0 7.0 5.8 4.8 3.4 9.0 = 35 KG
Using the ~ale:fe~ale sex ratio, the adjust~ent--(45*.53)+(35*.47) =40.3 kg-~ results in an esti~ated weighted-~ean weight through the winter period of 40.3 kg for the Bernhei~ Forest deer populations.
30
I
POPULATION PARAMETERS
Ecological MetabolisM
Ecological MetaboliSM of the weighted-Mean 40.3 kg deer was calculated with the following equation and rounded to the nearest 50 Keal per day:
ELMO = 1.8*70*(0.9*40.3)A0.75 : 1850 Kcals per day
Foraee required
The aMount of dry-weight forage required per day to satisfy the ELMO above is deterMined with the folloWing equation:
FRKO = 1850/(4500*OECO*0.82).
Using a digestible energy coefficient of 0.40, the folloWing equation provides an estiMate of forage required in kg per day (FRKO):
FRKO = 1850/(4500*.40*.82) = 1.25 Kg/day.
This value, 1.25 kg, equals about 2.8 pounds of forage (dry-weight basis) per day, or 560 pounds per deer for a 200-day period of plant dorMancy froM October to April. Reducing this by 10t to allow for the contribution of the fat reserve (see Table 7, page 30 and Figure 8, page 31), about 500 pounds of forage would be required per deer for the winter.
31
CARRYING CAPACITY AND POPULATION SIMULATIONS
Carrying capacity calculations should be ~ade on the basis of required in relation to resources available. In this analysis, energy is the resource considered, and calculations are ~ade for a period of plant dor~ancy.
resources nutritive
200-day
The nu~ber of deer-days supported by the forage available is deter~ined
with the following relationship:
Nu~ber of deer-days = forage available/forage required per day.
The nu~ber of deer supported through the winter is deter~ined with the following relationship:
Nu~ber of deer = forage available/forage required per deer for the winter.
The nu~ber of deer calculated with the relationship above is the carrying capacity; it is the population goal for a given area for a designated ti~e
period.
The a~ount of forage available has been deter~ined fro~ ~easure~ents on 121 field sites. Forage production patterns in ti~ber stands of different ages were illustrated in Figure 5 (page 16) and ~easured forage production in pounds per acre is given in Table 8 (page 26). After deter~ining carrying capacity, population si~ulations predict changes in the population in response to different co~binations of natality and ~ortality.
Carrying Capacity Calculations
The a~ount of forage required per day was calculated in the previous section. Since only part of the current annual growth of woody twigs should be re~oved
if plants are to re~ain vigorous, deer should be allowed only a fraction of the available growth. A 20% consuMption fraction for woody growth has been used in the calculations of carrying capacity in the woodland; this will allow for recovery of the vegetation and establish~ent of tree seedlings. Herbaceous growth in the forests is not available in the winter, which is when food resources li~it the carrying capacity. Since deer are selective when eating herbaceous plants, choosing only the palatable parts of herbaceous plants such as leaf and ste~ tips, a 4~ conSUMption fraction has been used in the calculations of carrying capacity in open lowland.
Calculations of the woodland carrying capacity, openland carrying capacity, and cOMbined carrying capacity of the Bernhei~ Forest are shown on the next page as four equations:
33
CARRYING CAPACITY AND POPULATION SIMULATIONS
BERNHEIM AREA: NUMber of deer-days = 69300/3.8 = 18237 deer-days, and NUMber of deer = 69300/500 = 139 deer.
KNOBS AREA: NUMber of deer-days = 68000/3.8 = 17895 deer-days, and NUMber of deer = 68000/500 = 136 deer.
OPENLAND: NUMber of deer-days = 1875/3.8 = 494 deer days, and NUMber of deer = 1875/500 = 4 deer.
COMBINED: NUMber of deer-days = 139175/3.8 = 36625 deer days, and NUMber of deer = 139175/500 = 278 deer.
The nUMber of deer supported by the woodland and openland forage cOMbined-- 278 deer--is the forage-based population goal for both the BernheiM properties. This goal provides for proportional use of range forage, and allows for range recovery.
Population SiMulations
ReMoval of deer to reach the calculated population goals was siMulated on a cOMputer prograM (Moen unpublished MS.) The prograM calculates the expected effect of reMoval of a fraction of the deer. The nUMber of deer in each sex and age class is accounted for, age-specific natality rates add fawns each year, and sex- and age-specific Mortality rates are calculated as values proportional to Male fawn survival. Population characteristics are calculated at the beginning and end of the SUMMer/fall period, the end of the reMoval period, and the beginning and end of the spring/winter period.
Inputs used in this population evaluation prograM represent reasonable biological estiMates of the deer population characteristics on the Forest. SUMMer survival of Male fawns was estiMated to be 0.80, and winter survival 0.85. Average Male yearling antler beaM diaMeter (YABD) was estiMated to be 13.5 MM. Inputs used are described below and nUMerical values are listed in Table 10.
Fawn Survival. An average Male fawn survival of 0.80 is used for each SUMMer. This is an approxiMate average denSity-independent fawn survival value deterMined in an in-depth population study in New York State (Moen and Sauer 1977). Neonatal fawn survival is dependent on weight at birth and on weather conditions during and shortly after parturition. Winter Male fawn survival is set equal to 0.85. FeMale fawn survival is slightly less than Male fawn survival.
Yearling Antler BeaM DiaMeter. As previously indicated (page 27) the YABD is a function of range condition. The fawn sex ratio is also related to range condition; good range conditions favor survival of the larger Male fawns in utero and hence affect sex ratio at birth. Male fawns are expected to survive in greater proportions, however, causing the fraction of feMales in the population to decrease, relatively, which in turn decreases the nUMber of reproductively active feMales in the next year.
34
CARRYING CAPACITY AND POPULATION SIMULATIONS
Fraction of Yearling Males in ~ Population. This input is used in the equations which generate the starting population in the population evaluation co~puter progra~.
The initial input of 0.40 was esti~ated fro~ the results of the 1984 hunt. Subsequent values of FYMP are calculated based on the results of the annual population si~ulations.
Fe~ale-to-~ale ratio in the yearline Bnd ~ population: This ratio is calculated on the basis of results of the first year's si~ulation.
~ re~oval ~ ~ ~. The nu~ber or percent of deer re~oved are entered yearly. The results of the February, 1984 hunt were entered to set up the first year. Re~oval
rates for subsequent years were entered sequentially. Antlered and antlerless deer were re~oved in the following proportions, respectively: 50% and 0%, 0% and 50%, 25% and 25%, and 50% and 50%. Results of these re~oval rates for the entire Bernhei~ property are illustrated in Figure 12.
Table 10. Population para~eters used in the population si~ulations.
MFSS MFSW YABD FYMP FRAP
0.80 0.85 = 13.5 0.40 1.05
Male fawn survival in the su~~er Male fawn survival in the winter Yearling antler bea~ dia~eter Fraction Yearling Males in Population Fe~ale-to-~ale ratio in the yearling and adult population
Initial populations: Bernhei~ Forest area = 612, Knobs Forest area = 338.
Re~oval of antlerless deer (~ale fawns, so~e yearling ~ales, and fe~ale deer of all ages) reduces the population ~ore than re~oval of antlered deer. A fe~ale yearling has the potential to produce 12-15 fawns during her reproductive lifeti~e, yet only one fe~ale offspring needs to survive to breeding age before the doe dies to keep the size of the breeding population constant. If ~ore than one survives the population will grow. The ratio of antlered to antlerless deer to be re~oved to keep the population size constant will vary with the sex ratiO in the population. This is why the evaluations need to be updated each year; co~puter-based infor~ation processing is designed for just such purposes.
35
READ Y-AXIS AS NUMBER OF DEER 400 + + 400
380 + + 380
360 + + 360
60 + + 60
40 + + 40
20 + + 20
YEARS
FiQure 12. Population size changes in relation to five re~oval rates on the Bernheil"l area.
36
MANAGEMENT OPTIONS
ManageMent of free-ranging populations of wild species is accoMplished best when the biological relationships between aniMal and range are understood. We hUMans share the land with wild species, and careful consideration of the Many diMensions involved in land use will result in reasonable nUMbers and resource use by all species. ManageMent options May be evaluated by siMulations which represent deer populations and predict population trends without the expense and delays associated with actual trials. This is analagous to financial analyses which May be cOMpleted for different rates of return; actual rates May not be known in advance, but various options and expectations are considered when Making decisions. In this report, the deer population has been described with the best available current data, and the expected effects of different Manage~ent options are discussed next.
Do Nothing
One Manage~ent option is to do nothing, to let "nature take its course." Man, by virtue of land use patterns that have developed for several centuries in this area, has Made it iMpossible for nature to fully take its course, ecologically. A "do nothing" approach to deer population control on the BernheiM Forest has resulted in population increa~es in the past (See Figure 3), resulting in daMage to nearby agricultural areas and affecting forest regeneration and understory co~position. Deer control the understory abundance, diversity, and COMposition on the Crane Me~orial Reservation and Wildlife Refuge in Ipswich, Massachusets (Moen 1984). At the BernheiM Forest, da~age to agricultural areas occurs before the deer affect understory co~position as greatly as the Crane areas have been affected.
Predators (poachers, dogs, coyotes, fox, bobcats) are not abundant enough on the BernheiM Forest to control the deer population, and without theM and such other natural eleMents as fire, ecological relationships are not co~plete. Further, the ecology of this area has been dOMinated by Man for over 200 years. What should be done to recover and perpetrate as ~any natural relationships as possible on the BernheiM Fore~t?
Feed the Deer
It is teMpting to consider feeding deer which are starving. A successful feeding prograM would be very expensive, would result in higher survival rates and more population growth, co~pounding the probleM of too Many deer for the carrying capacity of the land. There are also several practical probleMS associated with feeding deer. One, as rUMinants, deer need tiMe for the ~icroflora in the rUMen to adjust to new feeds. Thus a change in diet MUSt be Made over a period of ti~e. Two, feeding concentrates the deer, and this increases the likelihood of exchanges of paraSites between deer, and results in greater localized iMpacts on the vegetation. Three, costs of feeding an increasing deer herd would arise rapidly as the deer becaMe More dependent on an artificial food supply. Whenever there are too Many free-ranging deer for the habitat to support, SOMe ~ethod of herd reduction is necessary.
37
Reduce the Population
It is i~possible to keep deer herd nu~bers in ecological balance in areas such as the Bernhei~ Forest without periodically reducing the nu~ber5; ~an ~ust
assu~e the role of an effective predator. Reductions should occur until the population is reduced to the carrying capacity of the habitat, and then control ~easures should ~ini~ize population fluctuations fro~ year to year. Methods of population reduction need to be given careful consideration with regard to their feasibility and appropriateness for these areas. Several ~ethods are discussed briefly next.
Trapping
Trapping deer is a labor-intensive and capital-intensive activity that is not successful in reducing and controlling a deer population.
Hunting
Hunting is a cost-effective population control ~ethod (Giles 1978). Different for~ats ~ay be used, and co~puter-based analyses now ~ake it possible to consider a nu~ber of different for~ats. The for~ats considered are all subject to the ga~e laws of Kentucky, under the authority of the Kentucky Depart~ent of Fish and Wildlife Resources and their Ga~e Co~~ission. Hunts on a natural area such as the Bernhei~ Forest should be planned and regulated carefully, and ~anage~ent responsibilities need to be assigned to oversee the deer control progra~ at the Forest.
Open-to-the-public Huntina. Public hunting, i.e., anyone ~ay hunt without per~ission, is not desirable on the Bernhei~ Forest for a nu~ber of reasons, including high potential hunter density (35,000 hunters applied for a 1,350 per~its to hunt in February, 1984), the current Wildlife Refuge status of the Forest and the opposition of the Foundation Trustees to such uncontrolled public hunting.
Controlled Hunting. Controlled hunting i~plies the presence of a specified nu~ber of hunters, screened for their ability to handle firear~s
safely and accurately, and assigned to selected areas of the Forest. Experience with such controlled hunts at the Carey Arboretu~ in New York State has shown that such hunts beco~e ~ore successful each year as experience is gained by both ~anage~ent and the roster of hunters. A well-~anaged,
controlled hunt would be an econo~ical ~ethod of ~anaging the deer herd. Either the Kentucky Depart~ent of Fish and Wildlife Resources or personnel at the Bernhei~ Forest would have to assu~e responsibility for planning and ~anaging such a hunt.
Quota Huntina. A goal-oriented reduction progra~ could be set up on a trial basis on the Bernhei~ Forest, with reduction continuing until a designated quota has been reMoved fro~ the population. This reduction would be carefully ~onitored, with each ani~al inspected and its sex and age entered into a population progra~ in the COMputer which would continually update the predicted require~ents of the herd re~aining on the land, the reproduction expected at the next parturition, and the iMpact of these changes on next
38
MANAGEMENT OPTIONS
year's population. Quota hunting is ideally suited to critical and high­ da~age areas such as nature preserves, arboretu~s, orchards, vineyards and .truck far~s. Quota hunting ensures adequate re~oval, ~iniMizing the possibility of probleMs due to overpopulations recurring frOM year to year.
Quota hunting could be conducted with a wildlife re~oval perMit issued by the Kentucky DepartMent of Fish and Wildlife Resources. ReMoval perMits are issued when deer cause or have the potential to cause da~age to agricultural crops or property. The perMits are usually issued in retrospect; perMits are issued after cOMplaints are filed. The science and art of population control has now reached the point where probleMs can be prevented rather than cured, and that is a fundaMental characteristic of good ManageMent of any resource. Because of the extended period of tiMe during which Quota hunting could continue, ManageMent of such a hunt should be the responsibility of the BernheiM Forest personnel.
Deer populations, once reduced, will increase again unless control Measures are taken (See Fig. 3, p. 7). It is Much easier to Maintain control over annual increMents of deer populations than it is to allow theM to build up for several years and then try to reduce theM to Much lower levels. The population is stable when the natality and Mortality rates are equal.
39
MANAGEMENT RECOMENDATIONS
Manage~ent
opportunity population
of the deer population on the Bernhei~ properties presents the to i~ple~ent a herd control progra~ which will first reduce the
and then control it with a ~ini~u~ of effort and cost. Deer herd control is clearly necessary if population fluctuations are to be Further, as a society, we ought to recognize our effects on both ani~al populations, and to ~anage both of these natural responsibly, not allowing one to do~inate the other.
~ini~ized.
plant and resources
The population of deer before the 1984 reduction hunt was ~uch higher than the forage-based carrying capacity of the Bernhei~ Forest. Further, the deer were in poor physical condition, indicated by the low body weights and the nu~ber of fawns (22) found dead during the hunt. Although the deer population was reduced, further reductions are still necessary to get the nu~ber of deer down to a level which will allow for recovery and restoration of the vegetation.
A quota-based for~at is the best of the three options given in the previous section for an area such as the Bernhei~ Forest. Two ~ain advantages of a quota-based hunt are (1) a designated nu~ber of deer, sufficient to ~eet the population reduction goal are re~oved each year, and (2) hunting effort is diffused as fewer hunters are allowed on the Forest at a ti~e, but over a period of several weeks. Thus it should be safer and ~ore relaxing for those who enjoy hunting ~ore for the fun of being in the woods than for any other reason. Such a hunt could be ~anaged by Bernhei~ Forest personnel, in cooperation with the Depart~ent of Fish and Wildlife Resources.
Both antlered and antlerless deer should be re~oved under fairly intensive hunting pressure for the next three years. Such intensive hunting pressure is needed i~~ediately in order to ~ake less intensive hunting possible in the future. Cooperative efforts between Bernhei~ Forest personnel and the Kentucky Depart~ent of Fish and Wildlife Resources are strongly reco~~ended in the next three years as both parties gain experience with quota hunting as a ~anage~ent for~at.
41
MANAGEMENT RECOMMENDATIONS
BernheiM Forest Area. The inputs used for the initial population siMulations, described in Table 10 (page 35), were used in the siMulations used to calculate the nUMbers of deer which should be reMoved each year froM the BernheiM area. ReCOMMended reMoval rates of 20 to 40 percent of the antlerless deer and 20 to 30 percent of the antlered deer result in the harvests given in Table 11 and plotted in Figure 13. Note that, depending on harvest rates selected for antlered and antlerless deer, frOM 101 to 164 should be reMoved in 1985, 87 to 108 in 1986, 66 to 81 in 1987, and 18 to 65 in 1988, 8 to 55 in 1989, and 8 to 43 in 1990 frOM the BernheiM area. The lower nUMbers in 1988-1990 are due to intensive antlerless reMoval rates (307. and 40%) which keep the nUMber of breeding feMales low. All of these nUMbers are based on the Mortality and natality rates given earlier; the results are based on the assuMption that reproductive rates do not rise sharply and that fawn survival reMains at the level used in the analyses.
Table 11. The nUMber of antlered and antlerless deer which need to be reMoved frOM the BernheiM Forest area at the recoMMended reMoval rates.
1985 1986 1987 1988 1989 1990 Antlered/Antlerless
ReMoval rate (X) 20/20 20/20 20/20 20/20 20/20 20/20
Antlered 38 34 30 25 22 18 Antlerless 63 53 45 40 .l2 ~
Total 101 87 75 65 55 43
Antlered/Antlerless ReMoval rate (X) 30/30 30/30 30/30 15/15 10/10 10/10
Antlered 57 43 32 12 7 7 Antlerless 94 ~ 49 ~ .li 1.1
Total 151 111 81 30 18 18
Antlered/Antlerless ReMoval rate (X) 20/40 20/40 25/30 10/10 515 5/5
Antlered 38 31 31 9 4 4 Antlerless 12Q 77 ~ 1! ! !
Total 164 108 66 18 8 8
42
120 +
100 +
80 +
120 +
100 +
80 +
60 +
120 +
100 +
80 +
Male 20% Antlered
READ V-AXIS AS NUMBER OF DEER TO BE REMOVED
Male ----
1989
READ Y-AXIS AS NUMBER OF DEER TO BE REMOVED • lMale 20% Antlered
40% Antlerles s
+ 120
+ 100
+ 80
60
40
20
o 1990
NUMbers of antlered and antlerless deer to be reMoved froM the BernheiM Forest area each year. Initial reMoval rates in 1985 identify the graph, reMoval rates in following years are given in Table 11.
43
MANAGEMENT RECOMMENDATIONS
~ Forest ~ The recoMMended reMoval rates of between 20 and 40 percent of the antlerless deer and 20 and 30 percent of the antlered deer will reduce the population to the carrying capacity in 3 to 6 years. The nUMbers of deer which should be reMoved each year froM the Knobs Forest area are given in Table 12 and plotted in Figure 14. Note that 88 to 147 should be reMoved in 1985, 78 to 99 in 1986, 48 to 74 in 1987, 17 to 59 in 1988, 8 to 51 in 1989, and 8 to 44 in 1990. Again, the assuMption is Made that reproductive rates do not rise sharply and that fawn survival reMains at the level used in the analyses.
Table 12. The nUMber of antlered and antlerless deer which need to be reMoved froM the Knobs Forest area at the recoMMended reMoval rates.
1985 1986 1987 1988 1989 1990 Antlered/Antlerless
ReMoval rate (%) 20120 20/20 20/20 20120 20/20 20/20
Antlered 29 27 24 22 19 17 Antlerless 59 .51 .tl 37 .J.l n.
Total 88 78 68 59 51 44
Antlered/Antlerless ReMoval rate (X) 30/30 30/30 30/30 10/10 10/10 10110
Antlered 43 34 26 7 7 7 Antlerless ~ 65 48 11 11 11
Total 132 99 74 18 18 18
Antlered/Antlerless ReMoval rate (X) 20/40 20/40 20/25 10/10 5/5 5/5
Antlered 29 25 20 8 4 4 Antlerless 118 74 28 ~ ! !
Total 147 99 48 17 8 8
44
MANAGEMENT RECOMMENDATIONS
READ V-AXIS AS NUMBER OF DEER TO BE REMOVED 120 + + 120
100 + Male
80 + + 80
2: I"""I+J" __ + ___ '+i ___ + __ JlJi ___ + __ Jl+J ___ + ___ I+i ___ + ___ .+!---I
40
20
o 1985 1986 1987 1988 1989 1990
READ V-AXIS AS NUMBER OF DEER TO BE REMOVED 120 + + 120
Male = - 100 + Fel'llale = __ _ 30% Antlered
30% Antlerless + 100
60 + 1 i +
:: i 1i : : i : 1 I JI · · .: o +--- ----+--- +1 ___ +_- +1 ___ + ___ I+I ___ + ___ I+. ___ + __ Jl+. ___ +
+ 80
60
40
20
READ V-AXIS AS NUMBER OF DEER TO BE REMOVED 120 +
IMale + 120 -• 20% Antlered
• 80 + + 80 I 1 60 + 1 +
: 1 1 : 60
2: ~__ 1--+--1L_+--1L_+ ___ I+.---+---.+.---+---.... ---! 20
o
1985 1986 1987 1988 1989 1990
NUl'llbers of antlered and nonantlered deer to be rel'lloved frol'll the Knobs Forest area each year. Initial rel'lloval rates in 1985 identify the graph, rel'lloval rates in following years are given in Table 11.
45
MANAGEMENT RECOMMENDATIONS
Projections of deer nUMbers 2-4 years in the future are not Meant to be inviolate; inputs to the prograM such as SUMMer and winter fawn Mortality vary as weather and range conditions change. Data gathered on the aniMals reMoved are needed to Make adjustMents and recalculations each year which accurately reflect the changing conditions of aniMal and range. That i5 precisely why the COMputer is used; recalculations are quick and easy once the prograM teMplate has been set up. It should be eMphasized that the need to evaluate the ManageMent strategies iMpleMented Makes it necessary to have SOMeone responsible for updating ManageMent plans, recording deer data, Maintaining records, and evaluating the results frOM year to year.
ManageMent of deer populations at a nature center such as the BernheiM Forest is SOMetiMes controversial because of the traditions surrounding nature centers. They are thought of as places where all wildlife can live peacably together, and people who support nature centers are generally not in favor of hunting (Bowles 1981). Since deer are herbivores with a very high reproductive potential, they have a treMendous iMpact on vegetation when their nUMbers are high. They affect the abundance and diversity of plants, which in turn affects the abundance and diversity of aniMals.
High cash-value crop areas are another exaMple of the type of location where quota-hunting is deSirable and perhaps necessary. It is likely~ based on conditions in Many other states, that Kentucky DepartMent of Fish and Wildlife Resources will be forced into action concerning such areas in the near future if it hasn't been up to this tiMe. Quota-based hunts designed to MiniMize control effort and population fluctations frOM year-to-year provide the opportunity for real profeSSional and effective ManageMent where it is needed. The quota-hunt forMat described here provides the Kentucky DepartMent of Fish and Wildlife Resources with an opportunity to develop ManageMent experience in areas where deer population control is critical. This area could beCOMe a prototype for other critical areas in the future.The More traditional season-tupe forMat is still appropriate for those areas where deer ManageMent objectives are directed More toward recreational hunting, of course.
It is iMportant to reMeMber that profeSSional ManageMent options have not been readily available in the past because of the tiMe necessary for tabulating and evaluating the data. Now, with cOMputer-based inforMation processing, data can be entered directly into a COMputer which has been loaded with the appropriate software, analyzed in Minutes, and deCisions Made within days at MOSt. Further, this can ultiMately be done by personnel at the BernheiM Forest since COMputers are readily available at reasonable cost, and the software, in preparation by A.N. Moen, will be available soon.
The availability of low cost COMputing power, coupled with the availability of deer ManageMent prograMS at low cost, siMilar to state extenSion-produced COMputer prograMS for Managing woodlots, for exaMple, suggests that Many people could be in the deer Manage~ent business within a few years. At least, they will have opinions based on SOMe facts and potentially very powerful analytical prograMS. This Makes it iMperative that state wildlife agencies aSSUMe a leadership role if they are to be looked on as responsible profeSSional stewards of wildlife resources such as white­ tailed deer, and at the saMe tiMe being responsive to property owners and tenants who are the stewards of the land.
46
ECOLOGICAL CONSIDERATIONS
AniMal and environMent are inseparable and interactive; the status of one affects the status of the other. Natural areas are ecological units having particular size and diversity characteristics that allow both plants and aniMals to live in dynaMic balance with one another. Natural areas Must be of sufficient size for ecological relationships to develop. Such diversity develops only when no single cOMponent or few cOMponents dOMinate the area. While the BernheiM property is relatively large, it is very hOMogeneous--an even-aged hardwood forest--and deer have Made a noticeable iMpact on the forest.
Population Interactions
Deer on the BernheiM property spend the SUMMers spread out over a large area, but tend to Move to the lowlands and nearby agricultural areas in the fall and winter. The potential for agricultural daMage increases as the deer population increases. The effect of deer on both natural vegetation and agricultural crops can be severe. The establishMent of tree seedlings of preferred browse species can be prevented in years of high deer populations; the deer affect the future species cOMposition of the forest in this way.
Browse lines are evident in parts of the BernheiM Forest as a result of excessive foraging. Plant geoMetry and understory species cOMposition affect the Visibility of the browse line. Eastern Red Cedar and Virginia Pine, for exaMple, have very pronounced browse lines, and reproduction and new growth of these species is very liMited. A browse line was not observed on beech seedlings and saplings in any part of the Forest, however, since it is generally not a preferred browse species. Large nUMbers of beech seedlings and saplings are found in parts of the BernheiM and Knobs Forest areas; they are in a pOSition to increase relative to plant species which are preferred deer foods.
Spring wildflowers, which are as natural a part of forests as are the trees, can be severely iMpacted in years of high deer populations. Wildflowers can be browsed heavily before they reproduce or store enough energy to sprout the next year. TrilliuM flowers, for exaMple, weigh about 0.1 gM each, and the top part of the plant about 0.25 gM, so hundreds would be required to satisfy even a SMall part of a deer's daily diet (Moen 1984).
ManageMent of the habitat and nUMbers of different species is sufficiently well-developed as an art and science to prevent such environMental iMpacts, and to provide not only for the presence but also an appropriate abundance of both plants and aniMals, native and introduced. Rational ManageMent of deer populations in an ecological context is pOSSible, and benefits the ecosysteM as a whole.
47
48
SUMMARY
Metabolic energy require~ents and the a~ount of forage necessary to ~eet these require~ents have been calculated for white-tailed deer populations on the Bernhei~ Forest and Knobs Forest areas. The nu~ber of deer currently on these areas exceeds the nu~ber that should be supported by the available forage resources.
Forage production within reach of deer is low in the Mature hardwood forest which covers 97% of the Bernhei~ property. A target population of 200- 300 deer has been deter~ined fro~ carrying capacity analyses. Reductions in the nUMber of deer should follow a carefully-planned schedule; between 200 and 300 deer should be reMoved in 1985. Reductions should be followed by control of deer nu~bers in order to prevent a reoccurrence of over-population. COMputer-based population evaluations indicate that 20 to 100 deer would need to be re~oved annually in 1990 and subsequent years, depending on the ratiO of antlered/antlerless deer harvested in previous years.
Manage~ent of the deer population on the Bernhei~ property could serve as a prototype of intensive control, using quota-based hunting rather than season-based hunting. A designated nUMber of fe~ale and Male deer would be re~oved each year by qualified hunters who would be allowed to hunt for several weeks or even ~onths, until the quota was reached. This kind of hunting should be considered in areas where precise control of the deer population is necessary because of land use patterns such as orchards, vineyards, parks, and nature centers.
Since free-ranging deer are a public resource living on private land for the Most part, cooperative efforts between the wildlife agencies responsible for the deer and landowners and tenants responsible for the land are not only encouraged, but are necessary if Manage~ent is to proceed at the level of professionali5~ currently possible.
49
50
LITERATURE CITED
LITERATURE CITED
Anony~ous. Nu~ber 1. Bernhei~ Forest ArboretuM and Nature Center. Pa~phlet produced by the Isaac W. Bldg., Louisville, KY.
BernheiM Foundation, Inc., 536 Starks
AnonYMous. NUMber 2. 1984. BernheiM Forest ArboretuM and Nature Center. PaMphlet produced by the Isaac W. BernheiM Foundation, Inc., 536 Starks Bldg., Louisville, KY.
Bowles, M. 1981. Hunting policies on nature preserves and natural areas in eleven Midwestern states. J. Nat. Areas Assoc. 1(1 ):5-9.
Giles, R.H. Jr. 1978. Wildlife ManageMent. W.H. FreeMan and COMpany, San Francisco. 416 p.
Hicks, L.E. 1939. Report of Survey ~ade of Deer DaMage and Deer Control ProbleMs on the BernheiM Foundation Estate Area. Unpublished.
Medley, M.E. 1984. The Spontaneous Vascular Flora of BernheiM Forest, Bullitt County, Kentucky. Unpublished.
Moen, A.N. 1973. Wildlife Ecology; An Analytical Approach. W.H. FreeMan COMpany, San Francisco. 458 p.
Moen, A.N. 1976. Energy conservation by white-tailed deer in the winter. Ecology 57(1):192-198.
Moen, A. N. 1978. Seasonal changes in heart rates, activity, ~etabolisM and forage intake of white-tailed deer. J. Wildl. Manage. 42(4):715-738.
Moen, A.N. 1980-82. The Biology and ManageMent of Wild RUMinants. Parts I- VII. CornerBrook Press, Lansing, N.Y.
Moen, A.N. 1980. The Biology and ManageMent of Wild RUMinants; Part I. Physical Characteristics of Wild RUMinants. CornerBrook Press, Lansing, N.Y.
Moen, A.N. 1981. The Biology and ManageMent of Wild RUMinants; Part III. Physiology and MetaboliSM of Wild RUMinants. CornerBrook Press, Lansing, N.Y.
Moen, A.N. 1983. Lansing, N.Y.
Moen, A.N. 1984. Wildlife Refuge.
Agriculture and Wildlife ManageMent. CornerBrook Press,
Deer ManageMent at the Crane MeMorial Reservation CornerBrook Press, Lansing, N.Y.
and
Moen, A.N. and P. Sauer. 1977. Deer Populations and Harvest SiMulations. Pages 26-36 In Proceedings of the Joint Northeast-Southeast Deer Study Group Meeting, Blackstone, VA.
51
Moen, A.N. and C. W. Severinghaus. survival of white-tailed deer.
1981. Annual cycle weight equations and N.Y. Fish GaMe J. 28(2):162-177.
Moen, A.N. and C.W. Severinghaus. In press. universal key. N.Y. Fish GaMe J.
EstiMating nUMbers with a
Pierle, C.B. 1942. Deer DaMage report on the BernheiM Foundation Estate Area. Unpublished.
Robbins, C.T., A.N. Moen, and J.T. Reid. 1974. Body cOMposition of white­ tailed deer. J. AniM. Sci. 38(4):871-876.
Severinghaus, C.W. and A.N. reproductive rates of a of antler beaM diaMeter GaMe Journal 30(1):30-38.
Moen. 1983. Prediction of weight and white-tailed deer population froM records aMong yearling Males. New York Fish and
52