Comparative Summer Feeding Strategies of Arctic and Alpine Rangifer

Comparative Summer Feeding Strategies of Arctic and Alpine RangiferAuthor(s): Terje SkoglandSource: Journal of Animal Ecology, Vol. 49, No. 1 (Feb., 1980), pp. 81-98Published by: British Ecological SocietyStable URL: http://www.jstor.org/stable/4278 .

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Journal of Animal Ecology (1980) 49, 81-98

COMPARATIVE SUMMER FEEDING STRATEGIES OF ARCTIC AND ALPINE RANGIFER

BY TERJE SKOGLAND

Viltforskningen, DVF, Elgesetergt. 10, 7000 Trondheim, Norway

SUMMARY

Rangifer tarandus tarandus and Rangifer tarandus granti were studied during summer at the alpine Hardangervidda, Norway and the arctic coastal plains, Prudhoe Bay, Alaska.

(1) Alpine Rangifer followed a gradient of vegetation release from snow cover over a relief gradient, arctic plains Rangifer followed a gradient of vegetation release from a high water table following snow melt on the polygonated tundra.

(2) Both Rangifers showed a significant correlation between time spent in vegetation types and respective phytomasses.

(3) Esophagus fistula and rumen dietary sampling in relation to availability showed that arctic plains Rangifer cropped in proportion to availability while alpine Rangifer selected forbs.

(4) Intake from both areas by EF sampling was significantly correlated with site phytomasses.

(5) A comparison showed that Rangifer biomasses from five regions within the subarctic-subalpine-arctic zone were significantly correlated with average summer range phytomass density. It was concluded that intermediate-sized Rangifer combined high quantity selection with quality selection as resource density permitted.

INTRODUCTION

Recent studies during the International Biological Program on Rangifer tarandus granti J. A. Allen on the North American arctic plains (Prudhoe Bay, Alaska) (White et al. 1975) and on R.t. tarandus L. from alpine plateaus (Hardangervidda, Norway) (Gaare, Skogland & Thomson 1970; Gaare & Skogland 1971, 1975; Skogland 1974, 1975) have documented in detail the feeding patterns of the species. Skogland (1974, 1975) and White et al. (1975) used phytosociological criteria to document dispersal patterns in relation to relief and vegetation mosaics.

Recent use of the esophageal fistula technique in preference-selectivity studies (Van Dyne 1962; Lesperance et al. 1960; Strasia et al. 1970) was first adopted by Skjenneberg et al. (1971) on reindeer (R.t. tarandus) in Norway and the method was subsequently used during the Hardangervidda and Prudhoe Bay studies. Combined with rumen samples from culled wild stock and detailed analyses of the vegetation these provide the most detailed picture available of Rangifer selection patterns. Most of the work so far has been reported separately in various reports and publications. One of the objectives of this paper is to bring this knowledge together and analyse it in view of some recent findings on other ungulates. From the East African grasslands there is evidence, i.e. Jarman (1974); Bell (1969, 1971); Stewart (1971) that a variety of African ungulates exploit the available biota on the basis of specific selection patterns related to body size.

0021-8790/80/0200-0081$02.00 ?1980 Blackwell Scientific Publications

81



82 Rangifer feeding strategies

Rangifer is a medium sized ungulate with adult live weights of the order of 50-120 kg. During the winter most Rangifer populations that have been studied appear to sustain themselves on a diet in which lichens predominate while vascular green plants play a more dominant role during summer (Heptner, Nasimovich & Bannikov (1966) USSR, Kelsall (1968) Canada, Klein (1967) Alaska, Hjeljord (1975) Svalbard, Gaare (1968a) Scandinavia). While utilization of lichens as a major winter food appears unique to Rangifer the summer vascular plant exploitation pattern is more comparable to the adaptation of other ungulates at lower latitudes.

METHODS

Esophagealfistula sampling

One reindeer from Hardangervidda and two from Prudhoe Bay were fitted with a fistula and used to sample pre-selected sites during grazing periods. For details of the procedures see White et al. (1975) from Prudhoe Bay and Gaare & Skogland (1975) from Hardangervidda. After a 2-3 days' adaptation period the animals were timed during ingestion to obtain data on rate of intake from different vegetation types. The contents of each sampling that was egested into bags attached around the neck was analysed botanically by the microscope point reading method (Gaare 1968b; Galt et al. 1969).

With EF samples the intake period is known and the area from which the experimental animal is harvested can be described botanically. However, because the experimental EF reindeer were not tame enough they could not be allowed to roam free, and were tethered to a 20 m rope with a man at the end following the animal during sampling. Since it would be difficult to quantify statistically at what level the EF samplings represented the diet of the wild animals, samplings were restricted to one vegetation type each sampling period. This procedure also reduced some of the variability in plant species compositions from ground scores since variability between sociological units is greater than within each unit.

From Hardangervidda only one vegetation type was sampled during early and late growth season. At Prudhoe Bay five different vegetation types were sampled during the growth season corresponding to the number of types utilized by wild Rangifer.

Rumen sampling

Wild Rangifer were shot and samples from their rumens taken for botanical analysis using the same point reading method as for fistula samples.

Plant parts are more difficult to identify in rumen than EF samples due to their more fragmented nature in the rumen. Also rumen samples from wild animals usually reflect the intake over an unknown length of time prior to culling.

Vegetation sampling

The ground cover in pre-selected sites grazed during fistula samplings was described in detail in 33 x 100 cm plots placed randomly in each vegetation type. From Prudhoe Bay no previous phytosociological classification existed and S0rensen's index of similarity (Greig-Smith 1964) was used to distinguish types. For details see White et al. (1975). After the completion of this field study Webber & Walker (1975) completed a more detailed vegetation analysis for the Prudhoe Bay region. The results from Skogland in White et al. (1975) were largely confirmed by Webber's work. From Hardangervidda the vegetation classification scheme of Nordhagen (1937, 1943); Kalliola (1939); and Dahl



T. SKOGLAND 83

(1956) was used to identify plant alliances, henceforth termed vegetation types. Availabil- ity of the various vegetation types was found by a combination of ground-walked transects and aerial photo interpretation. Data sources from Hardangervidda were Tveitnes (1947); Skogland (1974); Hesjedal (1975), from Prudhoe Bay Skogland's ground transects in White et al. (1975) were combined with map transects (White et al. 1975).

Habitat dispersal patterns

Wild Rangifer were followed in the field on foot during daylight periods and all groups within sight were classified to phytosociological vegetation types every 15 min with the aid of 15-45 x binoculars. Concurrent with this the activity pattern was recorded for each group, determined as number feeding, walking, running or resting. Location of groups in relation to a relief gradient was also recorded.

Feeding rate

Within active feeding periods of groups in the field randomly selected group members of the various sex and age cohorts were timed with stop watches for feeding rate, i.e. the amount of the feeding time spent on actual ingestion expressed as a fraction of 5 min samplings. All observations that were interrupted by other activities such as resting, walking or running were discarded. The 5 min samplings were performed in the intervals between each 15 min recording of number of animals in vegetation types and number engaged in the various activities. The observed feeding rates of wild Rangifer were compared to that of the fistulated animals during ingestion trials.

Selectivity

The data on use of vegetation types, plant species contents of fistula bags and rumen samples were compared to respective availabilities obtained in vegetation transects and ground plots. Selectivity was expressed as Ivlev's (1961) index of selectivity. Confidence intervals on proportions of time spent in each vegetation type by Rangifer and on individual items in the diets were determined by the z-statistic from tables in Fisher & Yates (1975) following Neu, Byers & Peek (1974).

Nomenclature of plants follow Lid (1963); Nyholm (1954-1969); Hulten (1968); Dahl & Krog (1973).

Below (Table 1) is shown the scheme of vegetation types used in this study and their nomenclature.

RESULTS

Plant growth stage utilization

Figures 1 and 2 show the percentage of time Rangifer utilized the available vegetation types through the summer period. Spring growth at Hardangervidda started approxi- mately 1 month earlier than at Prudhoe; the beginning of June v. the beginning of July (in 1972). From Hardangervidda at the time of start of snow melt the heath communities (L-A, J-ts, P-Pv) were utilized. Generally, use of the snow-bed heaths, snow-bed meadows, and mires peaked sometime during July at time of release from snow cover (see upper part of Fig. 1). As senescence of plants started during August a decline in the use of meadows and snow-bed communities took place.

Rangifer on Hardangervidda followed the receding snow-line to explore the early stages of plant growth (see Table 2). During July 80% of Rangifer foraging was from South facing slopes, during July a reversed trend in utilization to North facing slopes was




TABLE 1. Vegetation types from the Hardangervidda alpine area

Key Plant alliance classification Zonation

Heaths L-A, Loiseleurio-Arctostaphylion low alpine

Kalliola -39 J-ts, Junction trifidi-scandinavicum mid alpine

Nordh. -36 P-Vm, Phyllodoco-Vaccinion myrtilli low alpine

Nordh. -36 K-D, Kobresio-Dryadion Nordh. -36 mid-high

alpine Snow-bed heaths N-Cb, Nardo-Caricion bigelowii low-mid

Nordh. -36 alpine C-Sh, Cassiopo-Salicion herbaceae low-mid

Nordh. -36 alpine Snow-bed meadows La, Lactucion alpinae Dahl -56 low alpine R-Od, Ranunculo-Oxyrion digynae mid alpine

Nordh. -36 P-Pv, Potentillo-Polygonion viviparum mid alpine

Nordh. -3-6 Mires O-Eh, Oxycocco-Empetrion hermaphroditi low alpine

Nordh. -36 C-cg, Caricion-canescentis-goodenowii low-mid

Nordh. -36 alpine Sm, Salicion mysinites Kalliola -39 low-mid

alpine

Vegetation types from the Prudhoe Bay arctic plains area

Key Vegetation types Heaths Dryas Dryas integrifolia M. Vahl. dominated low

ridges along drainages. Sand dunes Salix ovalifolia Trauitv. dominated unstable

dunes along the coast. Marshes Eriophorum marshes Eriophorum angustifolium Honck dominated

polygonal complexes with raised hummocks and grading into marshes.

Carex marshes Carex aquatilis Wahlenb dominated marshes or pools with a high water table.

Meadows Dupontia wet meadows Dupontia fisherii R. Br. dominated usually

wet, well drained meadows along brooks.

For reference to vegetation type distribution based on plant com- positional data see appendices in White et al. (1975).

TABLE 2. Percentage utilization of aspects on a relief gradient by alpine Rangifer at Hardangervidda. Data from Skogland (1974)

Aspects

Summer Sample season N NE E SE S SW W NW size

Early 1 0.5 32 54 12 1 190 Mid 37 8 4 4 6 6 35 158 Late 21 20 16 13 8 1 7 14 300



T. SKOGLAND 85 1300

1250 I Altitude m/above

11501 I I Heaths L-A

J-ts_ P-Vm

Snow bed P-Pv 1 Heaths N-Cb

C-Sh I La R-Od

Mires C-Cg S-M

Loise/eurio -Arctostaphy/ion

Juncion trlfidi scandinavicum

Phy/lodoco-Vaccinlon myrti if// and Pofenth/o-Polygon/on viviparl 100

75 i Nardo-Carlclon blge/owll 50 =

125 L

Lactuclon a/p/rnie O

CGriclon-conescentls goodenowii

Ronunculo -Oxyrlon dlgynae

Cassiopo-Sa/icion herbaceGe

June July August

FIG. 1. Percentage of time Rangifer utilized vegetation types at the alpine Hardangervidda. Upper part shows the mean altitudinal distribution of the herd. The second lower part of the figure shows the average dates of growth initiation of each type after release from snow cover. The width of the shaded areas in the lower part of the figure shows the mean time

Rangifer utilized each vegetation type.

apparent (65% of observation). Rangifer used a relief gradient of c. 1150-1300 m above sea level following the receding snow-line (Fig. 1). On the flat arctic tundra at Prudhoe the permafrost underlaid plains does not permit rapid run off of excess melt water. On the sloping alpine ranges this water is rapidly carried off and also soaks into the unfrozen ground. In the arctic evaporation from stagnant water pools in polygons must be a major factor in recession of the water table.

Figure 2 shows that Rangifer clearly follow a gradient of receding water table during the summer season at Prudhoe. Arctic Rangifer use a strategy of foraging along a gradient of plant emergence on the plains in response to water level recession, while alpine Rangifer forage in response to snow melt.

Hardangervidda and Prudhoe Rangifer explored most vegetation types during summer in succession of first availability. On days of above + 7 ?C temperatures (depending on




Sand dunes I

Heaths Proportion of vegetation types below the water table

Polygon marshes

Former lake beds

Wet meadows

Carex marshes

100

Sa/lx rotundlfo/iG snow bed heaths A 75 a

Sand dunes 150

25 3

Erlophorum polygon marshes 0

DuponfiG wet meadows

Former lake beds

CareX aquaGf/Is marshes

Early late July

FIG. 2. Percentage of time Rangifer spent in vegetation types at the arctic coastal plains Prudhoe Bay area. The intersection of the sloped thick line with vertically drawn lines from the time scale at bottom of the diagram indicates the approximate water table in the

vegetation types.

wind conditions) harassment by bloodsucking insects could occur (from about the beginning of July, White et al. (1975); Skogland (1974)). Hardangervidda Rangifer seek hilltops or snow fields for relief from insect harassment, while Prudhoe Rangifer move toward the coast to be cooled by the on-shore Beaufort Sea winds in the coastal sand dunes. The avian Diptera causing strong discomfort, mosquitoes (Aedes), warble flies (Oedemagena tarandi L.) or nose bot flies (Cephenomyia trompe M.) are very sensitive to winds. A decline to lower fly activity is found along a gradient from wet tundra (or mires and tall shrubs) to more windswept ridges, or snow fields (with lower surface temperatures).

Vegetation type selection

Tables 3 and 4 show analyses of availability and Rangifer utilization of vegetation types. Chi-square tests

(X(1) = 526.6, P < 0.00 I(alpine), X(4) = 56.76, P < OO01(arctic)) indicated that both Hardangervidda and Prudhoe Rangifer utilized vegetation types nonrandomly.

Highest selection was shown for snow-bed meadows which have the greatest plant species diversity over a gradient from low alpine to middle alpine zones (Skogland 1974). Intermediate selection was shown for chionophilous heaths with dominant shrub (Betula



T. SKOGLAND 87

TABLE 3. Utilization-availability analysis of alpine vegetation types at Hardangervidda, Norway

Use Availability Vegetation types* N Y.t % + S.E. Selectivity?

Heaths L-A 26 3.3 ?15 3.5 +19 0 J-ts 25 3.1 ? 1.5 12.2 ? 2.1 -059 P-Vm 130 16.3 ? 3.1 6.8 5.5 +0-41 N-Cb 99 12.4 ? 1.0 30.8 ? 5.2 +0-43 K-D 1 0.15 ? 0.3 0.05 0 Snow-bed meadows L a 187 23.4 ? 3.6 1.4 + 1.4 +0-89 P-Pv, R-Od 136 17.0 ? 2.9 1.55 ? 0.6 +0-90 Snow-bed heaths C-Sh 80 10.0 ? 2*5 11.5 ? 2.8 0 Mires C-cg 75 9.4 ? 2.5 15.5 ? 4.0 -0.24 S-M 34 4.3 1.7 3.0 +1.4 0 O-Eh, L-S 7 0.9 ? 0.8 0.9 ? 0.3 0 Unvegetated 6.7 + 2.0 - Other 6.3

800 100.0 100.0 * For nomenclature of types see Fig. 1. t ? 10%. of the z-distribution. I Data from Skogland (in preparation).

? Selectivity = U + A

TABLE 4. Utilization-availability analysis of arctic vegetation types at Prudhoe Bay, Alaska

Use Availability

Vegetation types* N Y?t S.D.4 Selectivity Heaths D-i with 21 associated 15.7 ? 5.2 5.3 ? 2.4 +0-50 S-r snow-bed 7 heaths Snow-bed meadows D-f 24 13.5 ? 4.9 3.9 ? 4.0 +0-55 Mires and marshes E-a 81 45-5 ? 71 52-2 15-0 0 C-a 23 12-9 ? 4.8 29-8 16-0 -0.40 Sand dunes 22 12-4 ? 4.7 7.9 0

178 100-0 100.0

* For nomenclature see Fig. 2. t ? 10%0 of the z distribution. I Availability from line transects ? standard deviations (n = 5).

nana (L.)) and grass cover (Deschampsia flexuosa (L.)). Xeric heaths were utilized in proportion to availability as was the snow-bed heath (C-Sh).

Mires were used in proportion to availability or selected against during summer. During late summer-early fall, low alpine mires were used to a higher degree than their availability (Skogland 1974). On the arctic plains with fewer types available the pattern was comparable with highest selection for snow-bed meadows (D-f. type) and the Dryas heath while mires were used in proportion to availability. Marshes were used more




toward the end of the season when drained of most excess water. Sand dunes were used in proportion to availability as relief sites.

Plant species selection

Table 5 shows that when the sample compositions of plant growth forms were nor- malized according to the time arctic Rangifer utilized each vegetation type EF and rumen sample compositions were not significantly different.

TABLE 5. Comparison of mean plant group compositions of rumen and EF bag collected samples from July at Prudhoe Bay

Rumen EF samples Woody 34.3 42.1 Grass-like 52.4 48.9 Forbs 10.4 7.1 Lichen 2.9 2-03

100.0 100-0 EF samples were meaned and

weighted according to the time Rangi- fer spent in the various vegetation types. On the basis of the Spearman Rank correlation cofficient r = 0.991, P < 0.01.

Tables 6-7 show the selectivity ratings from the alpine area based on rumen and EF sampling. EF samples were collected from a composite representing the major vegetation mass on the summer range. Rumen samples are thought to express harvesting from a composite of exploited vegetation types at the day of culling. Since EF and rumen samples represent different proportions of the available vegetation I compared selectivity ratings to test whether they represented dietary selection differently. The two measures were correlated (P < 0.01, Spearman Rank correlation test). Sampling the major vegetation types during the summer from Prudhoe is shown in Table 8.

Highest selection was shown for shrubs, Salix rotundifolia L., S. ovalifolia Trautv. S. arctica Pall. Two Cyperaceae had intermediate rating (Eriophorum angustifolium Honck. and Carex scirpoidea Michx.). From the alpine area, forbs had highest selectivity ratings (Tables 5-6) (Alchemilla glabra Neyg., Solidago virgaurea L., Gnaphalium spp. Hieracium alpinum L., Rumex acetosa L.) and the second highest rating was shown for the leaves of the shrub Betula nana; third was the lichen Cetraria islandica (L.) and the thin- leaved grass Deschampsia flexuosa.

Overall, shrubs were selected from the alpine area in late July. Skogland & Gaare (in preparation) showed that at the beginning of June at Hardangervidda Salix was selected. Sampling from both areas at the end of July showed selection against shrubs, at a time when most leaves had matured.

Lichens are selected throughout most of the growth season when not dry and quickly gain the major selectivity rating when emergent phase vascular growth forms become scarce, and when flowering heads of forbs mature, but even when emergent and early flowering phase growth forms of vascular plants are available Cetraria lichens were selected. At the Prudhoe sites the largest proportion of species were cropped in proportion to availability.

Dispersal and consumption in relation to phytomass

The regression of above-ground phytomass from each vegetation type with the percentage time Rangifer spent in each type showed a significant positive correlation (r =



T. SKOGLAND 89

TABLE 6. Utilization-availability analysis of alpine plants from July rumen samples (data from Skogland & Gaare in preparation). See footnote*

Rt At E = R-A

WOODY

Betula nana L. 1.05(0.9-1-2) 7.88 -0-76 Salix herbacea L. 9.56(8.0-11.1) 17-64 -0.3 Salix lapponum L. 2-03(1-3-2-7) 1.47 0 Vaccinium myrtillus L. 0.84(0.4-1-3) 1.69 -0-34 Vaccinium vitis-idea L. 0.91(0.4-1-4) 1.83 -0-34 GRASSES, SEDGES

Anthoxantum odoratum L. 3.06(2-2-4-0) 4.0 -0-14 Carex bigelowii Torr. 11.94(10.2-13-6) 9.57 +0-11 Deschampsia caespitosa (L.) 2.84(2-0-3-7) 4.75 -0-25 Deschampsia flexuosa (L.) 13-9(12.1-15-7) 16.73 -0-09 Eriophorum angustifolium Honck 7.9(6-5-9-3) 3-17 +0-43 Festuca ovina L. 1-68(1-0-2-4) 2-9 -0-27 Juncus trifidus L. 1.38(0.8-2-8) 7.76 -0-7 Poa alpina L. 7.97(6-6-10-0) 0.94 +0 79 FORBS

Alchemilla glabra Neyg. leaves 1-73(1-1-2-4) 0-14 +0-85 Gnaphalium norvegicum Gunn. 2-16(1-4-2-9) 0.21 +0-82

leaves Hieracium alpinum L. flower heads 0.56(0.2-1-0) 0.09 +0-7 Polygonum viviparum L. leaves 1.42(0.8-2-0) 1-72 0 Solidago virgaurea L. flower heads 1-76(1-1-2-5) 0-08 +0-9 LICHEN

Cetraria islandica (L.) 4.37(3-2-5.5) 1-13 +0 57 Cetraria nivalis (L.) 2.37(1-6-3-2) 2.23 0 Cladonia mitis Sandst. (some C. 10-79(9-2-12-4) 5.66 +0-29

alpestris L. included) C. unicialis (L.), C. gracilis (L.), 5.55(4-4-6-7) 1-05 +0-69

C. rangiferina (L.) Stereocaulon paschale (L.) 1.2(0.6-1-8) 0-37 +0-51 MOSSES

Dicranum fuscesens Sm. 0.54(0.005-1-1) 2.32 -0.75 Pleurozium schreberi (Brid.) 1.15(0.006-2-3) 1-42 0 Polytrichum juniperinum Hedw.} 1.05(0.9-1*2) 3X23 -0-51 Polytrichum communis Hedw. f

99.7 100-0

* Plants identified in ground scores but not ingested are not included. t R = mean rumen contents from 12 samples with the 90%0 confidence intervals

from the z-statistic. t A = weighted average availability of plant species from ground scores in all

vegetation types utilized by wild Rangifer and weighted according to the availability of the various vegetation types on the summer range. Plant species scores are from 238 33 x 100 cm plots in Skogland (1974).

0.94, P < 0.001). The range of mean live standing crops of vegetation types was marked on Hardangervidda, varying from 18-117 g DM gm - 2. From Prudhoe less detailed information is available on plant production but White et al. (1975) collected samples from five sites during 1973. The range of live standing crops was much narrower in the arctic coastal plains, live mass was in the order of 25-50 g DM m-2. A large proportion of above-ground phytomass was standing dead and unlike the Hardangervidda Rangifer at Prudhoe they consumed a significant proportion of dead Cyperaceae from Eriophorum marshes. (See Table 7.) Including live and dead phytomass from this site (the closed triangle in Fig. 3) the combined data from both areas were best fitted by the equation

Y = 1.07X?'72.




TABLE 7. Utilization-availability analysis of alpine plants from July esophagus fistula samples

EF* At Et WOODY Betula nana L. 12.4(10.0-14.4) 2.9 ? 0.74 +062 Empetrum hermaphroditum Hagerup. 0-2 + 0.1 -1 Lycopodium alpina L. 1.8 ? 1-1 -1 Salix herbacea L. 7.2(6.0-8.7) 15.6 ? 4.4 -0-37 Salix lapponum L. 3.1(2.0-4.0) 1.8 ? 1.8 0 Vaccinium myrtillus L. 0-02(-0-1 + 0.1) 1.1 ? 0.6 -0-97 Vaccinium uliginosum L. 0-04(-0.1 + 0-2) 0.1 ? 0.1 0 GRASSES, SEDGES

Anthoxantum odoratum L. 1.0(0.4-1.6) 1.1 ? 0-4 0 Carex bigelowii Torr. 6.1(4.7-7.5) 9.2 ? 3.2 0 Deschampsiaflexuosa (L.) 12.6(11.0-14.6) 7-7 ? 3.8 0 Eriophorum scheuzeri Hoppe 0-1(-0.1 + 0.3) 1-4 ? 1.4 0.87 Festuca ovina L. 0.1(-0-1 + 0.3) 0.4 ? 0-4 0 Luzula sudetica (Wild.) 0-2 ? 0-1 -1 Juncus trifidus L. 0.2(-0.1 + 0.5) 1.8 ? 1-0 -0.8 Nardus stricta L. 6-4 ?25 -1 FORBS

Hieracium alpinum L. 20.0(17.6-22.4) 2.0 ? 0.9 +0-82 Rumex acetosa L. 6.7(5-2-8-2) 0-5 ? 0.4 +0-86 Rubus chamaemorus L. 0.2(-0.1 + 0.5) 2-1 ? 16 0 Solidago virgaurea L. 13.6(11.6-15-6) 0.6 + 0.3 +0-92 Trientalis europeae L. 0-2 ?01 -1 LICHEN

Cetraria nivalis (L.) 0.2 ? 0.2 Cetraria islandica (L). 11.4(9-5-13.3) 6.8 ? 1.8 +0-25 Cladonia alpestris L. 0.7(0.2-1.2) 11.4 ? 4.1 -0-88 Cladonia bellidiflora (Arch.) 1.0 + 0-4 -1 Cladonia coccifera (L.) 0.2 ? 0.2 Cladonia deformis (L.) 0-2 + 0-1 -1 Cladonia gracilis (L.) 0.5(0.1-0.9) 1.8 ? 0.7 -0.57 Cladonia mitis Sandst. 3.2(2-2-4-2) 4-2 ? 1.3 0 Cladonia uncialis (L.) 2-2 + 0-7 -1 Stereocaulon paschale (L.) 0.1(-0.1 + 0-3) 0.1 ? 0.1 0 Ochroleucia sp. 0.2 ? 0-2 MOSSES

Bryum sp. 1-7+0-9 -1 Dicranum fusescens Sm. 5-6 + 2-4 -1 Polytrichum communis Hedw. 0.3(0-0.6) 5.8 + 2.2 -0.90 Drepanocladus uncialis (Hedw.) 0.7 ? 0.7 Pogonatum alpinum Rohl. 0.4 ? 0.4

99-6 99.6

* EF = mean esophagus fistula sample contents (0%,) (n = 12) with the 900% confidence interval from the z-statistic.

t A = mean availability from ground plots ? standard errors (n = 14). 1 E = selectivity.

Based on the ingesta collected by the fistulated animals the mean intake per time unit (g DM min- 1) was obtained from nine sample sites. Figure 4 shows the mean intake rates plotted over standing crops from each sample site. A positive significant correlation (r = 0.89, P < 0.001) was found, best fitted by the equation

Y= 2153 + 7*67InX.

Feeding rates between wild Rangifer at Prudhoe and Hardangervidda shown in Table 9 indicate that lactating does did not have significantly different feeding rates while other



T. SKOGLAND 91

TABLE 8. Utilization-availability of arctic plants from July esophagus fistula samples

EF* At Et

WOODY Arctostaphylos rubra (Rehd.-Wils.) 0.66(-0.05 + 0.17) 1.3 ? 0-8 -0-88 Cassiope tetragona (L.) 0-8 ? 0.8 -1 Dryas integrifolia M. Vahl. 3.2(2-4-4-0) 13-3 ? 1-9 -0.61 Salix arctica Pall. 5.9(4-8-7-0) 2.9 ? 0.6 +0-34 Salix ovalifolia Trautv. 25.2(23.2-27.2) 5.6 ? 1.1 +0-64 Salix lanata L. 0.4(0.1-0.7) 0-9 + 0-3 0 Salix pulchra (Cham.) 2.3(1.7-3-0) 2.0 ? 0-6 0 Salix reticulata L. 0.6(0-2-1-0) 2.5 ? 0.6 -0-61 Salix rotundifolia L. 5.4(4-3-6-5) 1-1 ? 0.4 +0-66

GRASSES, SEDGES

Arctagrostis latifolia (R.Br.) 1-0 ? 0.5 -1 Arctophila fulva (Trin.) 0-2 ? 0-2 -1 Alopecurus alpinus L. 0.06(-0.05 + 0.17) 0.2 ? 0.08 0 Carex aquatilis Wahlenb. 6.8(5.6-8.0) 5.4 ? 1.2 0 Carex membranacea Hook. 2-5 + 0.5 Carex scirpoidea Michx. 9.1(7-7-10.5) 1.4 ? 0.5 +0-33 Carex rupestris All. 0.6 0-3 Dupontiafisherii R.Br. 3.6(2-7-4-5) 5-3 ? 0-9 0 Equisetum variegatum Schleich 0.2(0-0.4) 1.9 i 0.7 -0-81 Eriophorum angustifolium Honck 20.5(18.6-22-4) 12.7 ? 1.6 +0-23 Eriophorum scheuzeri Hoppe 0.01(-0.04 + 0.06) 2.4 ? 06 -0.99 Elymus molli (Trin.) 0.3(0.1-0.5) 0.5 ? 0.3 0 Juncus biglumis L. 1.1 ? 0.7 -1 Poa alpina L. 0.1 ? 0.07 -1 Festuca rubra L. 1.3 ? 0.9 -1 Standing dead (Cyperacea) 12.3(10.8-13-8) 26.2 ? 21 -0-36

FORBS

Astragalus spp. 0.07 ? 0.05 -1 Artemesia sp. 0.2(0-0.4) 0.2 ? 0-09 0 Cardamine pratensis L. 0.01(-0.04 ? 0.06) 0.3 ? 0.1 0-94 Draba alpina L. 0.2(0-0.4) 0.2 + 0.1 0 Oxytropis arctica R.Br. 0.1(-0.1-0.3) 0.8 + 0.3 -0-78 Pedicularis arctica R. Br. 0.1 + 0.07 -1 Pedicularis capitata Adams 0.03 ? 0.03 -1 Pedicularis sudetica Willd. 0.3(0-0.6) 0-3 + 0.1 0 Polygonum viviparum L. 0.3(0.1-0.5) 0-5 ? 0.2 0 Polemonium boreale Adams 0.09(-0.05 + 0.23) 0.8 ? 0-4 0 Parrya nudicaulis L. 0-2(0-0.4) 0.1 + 0-07 0 Primula borealis Duby 0.09(-0.05 + 0.23) 0.1 ? 0.07 0 Ranunculus nivalis L. 0.02 + 0.02 -1 Saxifraga cernua L. 0.4 ? 0.3 -1 Saxifraga hirculus L. 0.4(0.1-0.7) 0.8 ? 0.2 0 Saxifraga oppositifolia L. 0.8 ? 0.3 Silene acaulis (L.) 0.09 ? 0-09 -1 Stellaria crassifolia Ehrh. 0-01(0-04 + 0.06) 0.09 ? 0 06 0 Valeriana capitata Pall. 0.09(-0.05 + 0.23) 0-2 + 0.1 0

LICHEN

Cetraria ericetorum L. 0.06(-0.05 + 0.17) 0.04 ? 0.04 0 Dactylina arctica (Hook.) 0.2(0-0.4) 0-4 + 0-3 0 Thamnolia vermicularis (Sw.) 2.1(1.4-2-8) 1.1 ? 0 5 0

100-8 100.6

* EF = mean esophagus fistula sample contents (%) (n = 20) with the 90% confidence interval from the z-statistic in parentheses.

t A = mean availability (0%,) from ground plots (n = 108) ? S.E. I E = selectivity. Mosses were not recorded in EF samples and are excluded from availability.




IL> A

v 4 a) > 40 -

' 30 -

E0~~~~~~~~~ 20

-

a_ 0 20 40 60 80 100 120

Mean I ive aboveground vascular stand'ing

crop,g DM m-2, in each vegetation type

FIG. 3. Regression between mean phytomass per vegetation type and the percentage of time Rangifer spent in each type. Phytomass data from Wielgolaski (1975), Hardanger- vidda, and White et al. (1975), Prudhoe Bay. Percentages of time spent by Rangifer in each type are from Tables 3-4. 0 Hardangervidda A Prudhoe Bay. The Eriophorum marsh site is given with phytomass data for live and dead above ground (see text for explana-

tion).

TABLE 9. Mean ? standard errors of feeding rates of different size-sex classes of Rangifer from Hardangervidda and Prudhoe Bay study areas

Hardangervidda Prudhoe Bay Early summer Late summer Summer

Size-sex classes N x + S.Ef i X I, S.E. N x ? S.E. Velvet bucks, a 7 80-7 3-3, 31 76.9 2*2 22 60-4 4.3 Adult does 49 78.3 17 Lactating does 61 81-4 1-4 22 79.5 2.3 Barren does and 13 77.7 3-3 6 67.5 6.0

yearlings

cohorts showed significant differences. Arctic plains males and barren and yearling females spent more time searching than alpine Rangifer at Hardangervidda. Since more search time will lower the effective food intake rate and the mean intake rate at peak availability at Prudhoe was 2.29 gDM min-I compared to a mean 6.54 g DMmin'- at Hardangervidda it appears clear that alpine Rangifer at Hardangervidda had a higher intake rate per unit of effort than plains Rangifer.

The data presented in this section point to a strategy of quantity selection by Rangifer. Admittedly the data on which this conclusion is made are scanty and some of the samples small, but collectively they point to a clear trend of optimizing intake by concentrating

in the most productive parts of the summer ranges when allowed to express selection

uninterrupted by insect or other harassment.

Comparison with other arctic-alpine herds

A regression of regional average above-ground phytomass (Table 11) with Rangifer

summer densities (Table 10) shown in Fig. 5 was best fitted by the equation

Y= 0=6X'67

The correlation was significant (r = 0.96, P < 0.001). Table 10 shows that the difference

between the smallest-sized animals and the largest is marked, more than double. Also



T. SKOGLAND 93

* 14 E

L 12 0~~~~~ 0~~~~~

4)C -o>

4i)

6 0

cO) 4 ~ L

2

0 20 40 60 80 100 120 Mean live aboveground vascular standing

crop g DM m-2 in each vegetation type

FIG. 4. Regression between above ground live vascular phytomass and intake rate, expressed as the ingesta collected per time unit during esophagus fistula sampling. Body weights of sampling animals were 83 kg at Prudhoe Bay and 45-54 kg at Hardangervidda. 0 alpine sites at Hardangervidda from June-July, A arctic plains sites at Prudhoe Bay from July. Esophagus fistula data from White et al. (1975) and Gaare & Skogland (1971).

Plant data from White et al. (1975) and Wielgolaski & Kjelvik (1975).

3 0

en O /

00~~~~~~~~

'a) 0

C1 C

E~~~~~~~

O 2

QE 0

CIj

E

c ~~~ . I I I I I I

1. 5 2 205

Log10 aiverabge green vascular-lichen aboveground phytomsse, g DM 2,from each region

FIG. 5. Regression between live above ground phytomass and Rangifer biomass from various circumpolar regions. 0 Agapan station, Taimyr region in the subarctic in summer; 0 Hardangervidda, alpine region in summer; Fl Kevo station in the subarctic boreal forest-heath tundra ecotone in summer; A Nordenskioldland, arctic island in summer; A Reinsdyrflya, arctic in summer, a Prudhoe Bay, arctic plains in summer.

(See Tables 10 and 1 1 for references to individual site data.)




TABLE 10. Biomass data from various Rangifer herds

BW* Stocking rate Region Area kg N km - 2 References

High arctic Nordenskioldland 42.2 3.4-5.6 Krog et al. (1976), Island Reinsdyrflya Alendal, & Byrkjedal

(1976), Reimers (1977) Alpine Hardanger- 55 13 This study

vidda Subarctic Kevo 60 4 Fagerhaug (1976)

coniferous- Varo (1972), tundra ecotone Kallio (1975)

Arctic plains Prudhoe Bay 78 0-46 White et al. (1975) Subarctic tundra Taimyr 90 13-5 Vassiljevskaja

90 13.5 et al. (1975)

* Body weights are calculated as the mean population weights based on approximate age and sex structures.

TABLE 1 1. Regional phytomass data

Mean vascular-lichen Region phytomass (g DM m-2) References

Agapan, subarctic tundra 314.5 Vassiljevskaja et al.

(1975, p. 149) Kevo,

subarctic boreal forest 185.75 Kjelvik & Karenlampi (1975, ecotone pp. 113, 117).

Hardangervidda, subalpine tundra 219.5 Ostbye et al. (1975, p. 234)

Prudhoe Bay, arctic plains 41.06 White et al. (1975, p. 169)

New Siberian Island, Franz Josef Land, Aleksandrova (1958, 1969) High arctic islands 129-185* Cited by Bliss et al.

(1973, p. 368).

* Including cryptogams with mosses not excluded.

stocking rates varies much between the different areas. The Kevo data were taken from domestic Rangifer occupying that region (Kallio 1975). Since domestic stock are not allowed to disperse as freely as wild stock this could be a source of error. Data from two subpopulations of Svalbard Rangifer were plotted against primary productivity data from the nearby Franz Josef Land, and the more eastern but at same latitude New Siberian Islands (Aleksandrova 1970). The surprisingly high biomasses of Svalbard Rangifer were plotted against primary productivity including bryophytes. Unlike other Rangifer populations mosses are found to be ingested in large amounts, constituting up to 5000 of diets at times (Hjeljord 1975) in Svalbard Rangifer. The Svalbard data are from two distinct areas, fertile valley systems and flat polygonal plains. According to Aleksandrova (op. cit.) these physiognomic differences result in different primary productivity and Rangifer data were plotted against moss-lichen polygon site data and herb-dwarf shrub- moss site data. Bliss et al. (1973) showed that there are small variations in high arctic primary productivity from different study areas so the error involved in using plant production data from other areas than Svalbard could be small.



T. SKOGLAND 95

DISCUSSION

Alpine Rangifer selected the herbaceous layer as well as lichen and to some extent thin- leaved grasses and prostrate shrubs while arctic plains Rangifer expressed a less clear selection for particular strata of the vegetation but cropped most plants in proportion to availability, even cropping a high proportion of standing dead Cyperaceae. This apparent lack of selection by arctic plains Rangifer is probably an effect of low range productivity. The frequency of insect harassment from Hardangervidda and Prudhoe Bay were probably not different enough to account for the differences in selection intensity. In order to express high selection, search times would have to be too high for requirements to be met, and this is particularly evident for lactating females, where search time was kept to a minimum. Skogland & Gaare (in preparation) showed a positive significant correlation between highest total non-structural carbohydrate levels and a negative significant correlation between N/fibre ratios and the selection indices of plants during both summer and winter at Hardangervidda. Skogland (in preparation) also showed that there was a positive significant correlation between proportions of plant species from Hardangervidda July rumen samples compared to mean and live phytomass of each plant species. Wielgolaski (1975) showed that the penned domestic sheep (Ovis aries) at the Stigstuv sites selected vascular shoots of highest TNC concentrations.

Most Rangifer herds have separate winter and summer ranges on the Eurasian and North American mainlands. Some of the arctic island herds show a less marked seasonal movement but do more altitudinally, when permitted by the topography, from valley bottoms in summer to ridges and plateaus in winter (Egorov 1967; Kelsall 1968; Hjeljord 1975).

Generally, mainland winter ranges are located in the ecotone between tundra and taiga in the subarctic region, usually in a continental climatic zone, while summer ranges are located near the arctic coast lines. The alpine Rangifer at Hardangervidda move seasonally clockwise from the eastern winter ranges in a continental climatic zone westward into a more steeply graded summer range in the western part of the alpine plateau with a more oceanic climate. Arctic coastal plains Rangifer at Prudhoe mostly wintered in the northern foothills and south of the Brooks Range although a few winter on the coastal plains (White et al. 1975).

Rangifer, when not restricted, thus follow a shoot-tissue-high TNC concentration cycle extending over most of the summer season when the range gradient is steep enough. The animals disperse in a manner that combines high phytomass-high TNC concentrations per unit of vegetation thus securing maximum nutrient retrieval. This was achieved by a regular seasonal movement pattern (Skogland 1974) along learned routes of access. Plant growth during the 24 h diurnal cycle of light in the arctic and partially in the alpine location (60?N) is rapid in prostrate chamaephytes and hemicryptophytes which con- stitute the major part of the vegetation growing in the microenvironment near ground surface where daytime temperatures far exceed ambient temperatures when the ground is bared of snow or water (Bliss 1962). The alpine area with a steeper relief gradient and wider variation in aspect creates a wider range of microclimatic conditions over the season thus allowing for a more diversified plant community mosaic, broadly 12 alliances v. 5 associations.

Over a 4-year period alpine Rangifer seasonal home range occupancy was predictable. Alternatively in arctic Rangifer the gradient of water table recession is followed. The lack of a steep gradient does not permit rapid run off of excess water and less favourable




plant growth conditions exist, thus providing a less favourable niche where seasonal occupancy becomes more opportunistic. Rangifer occupation of the Prudhoe region was unpredictable during the period of this study (White et al. 1975).

It has been postulated from the Bell-Jarman hypothesis by Geist (1974) that ruminants adopting a feeding strategy based on highly digestible forage will be small-bodied. Rangifer, irrespective of subspecies, must be categorized as intermediate in body size and in its apparent ability to adopt quantity as well as quality selection dependent on density of highly digestible forage (flowers, sprouting shoots and lichens) over a productivity gradient. By non-random dispersal and morphological adaptation to a highly mobile harvesting technique they effectively concentrate the intake of highly digestible foods. The evidence from this study suggests that summer dispersal is primarily determined by vascular green phytomass but lichens are found in most mesic vegetation types and are preferred when not dry irregardless of spatial density. Lichens of the genus Cetraria and Cladonia are in most cases highly digestible with a rapid turn-over rate in the rumen (White et al. 1975, 1977; Jacobsen & Skjenneberg 1975) and their high density- accessibility all year provides a readily available source of carbohydrate maintenance energy, but protein for growth and reproduction must be cropped from the vascular strata. Coe, Cumming & Phillipson (1976) showed that East African large herbivore biomass-densities were significantly correlated with primary productivity in semi-arid regions. Likewise Bobek (1977) showed that roe deer (Capreolus capreolus) in temperate- coniferous regions of Poland had stocking rates significantly correlated with summer above-ground phytomasses.

This study suggests a similar relationship between average regional primary production and Rangifer biomass-density within the northern circumpolar region.

ACKNOWLEDGMENTS

The study was supported by funds from the Norwegian National IBP committee, section PT-UM, the Direktoratet for Vilt og Ferskvannsfisk, Trondheim, Norway and the US IBP Tundra Biome program. I am particularly grateful to cand.real. Eldar Gaare for my participation in the Norwegian reindeer project, for all help, discussions and criticisms, for office and laboratory facilities at the Institute in Trondheim, to Drs R. G. White and J. Luick for my participation in the US IBP program, and to R. G. White for co-operation in the field and subsequent help, discussions and criticisms during his stay in Trondheim, and to Gosta Hanseon for rumen contents analyses. Without the full support by E. Gaare, R. G. White and J. Luick this international study could not have taken place. Dr D. R. Klein, University of Alaska kindly provided critical comments on the manu- script.

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T. SKOGLAND 97

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(Received 6 October 1978)



Documents

Comparative Summer Feeding Strategies of Arctic and Alpine Rangifer