Habitat Selection by Blanding's Turtles ( Emydoidea blandingii ) in a Relatively Pristine Landscape

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Habitat Selection by Blanding's Turtles (Emydoidea blandingii) in a RelativelyPristine LandscapeAuthor(s): Christopher B. Edge, Brad D. Steinberg, Ronald J. Brooks, Jacqueline D. LitzgusSource: Ecoscience, 17(1):90-99. 2010.Published By: Centre d'études nordiques, Université LavalDOI: http://dx.doi.org/10.2980/17-1-3317URL: http://www.bioone.org/doi/full/10.2980/17-1-3317

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17 (1): 90-99 (2010)

Habitat selection studies document habitat and resource availability and patterns of their use by animals (Alldredge

& Griswold, 2006). The aim of these studies is to under-stand where animals are more likely to occur, which is necessary to understand their life history and general ecol-ogy (Manly, MacDonald & Thomas, 1993), especially for species at risk because loss of habitat is the largest threat to their survival (Dobson, Bradshaw & Baker, 1997; Wilcove et al., 1998; Venter et al., 2006; Walker & Preston, 2006). Studies of habitat selection are often conducted in degraded

Habitat selection by Blanding’s turtles (Emydoidea blandingii) in a relatively pristine landscape1

Christopher B. EDGE2, Department of Biology, Laurentian University, Sudbury, Ontario

P3E 2C6, Canada.

Brad D. STEINBERG, Ministry of Natural Resources, Algonquin Provincial Park,

Whitney, Ontario K0J 2M0, Canada.

Ronald J. BROOKS, Department of Integrative Biology, University of Guelph,

Guelph, Ontario N1G 2W1, Canada.

Jacqueline D. LITZGUS3, Department of Biology, Laurentian University,

Sudbury, Ontario P3E 2C6, Canada.

Abstract: Identifying habitats in which a species is likely to be found is extremely important for understanding the life history and general ecology of the species. Studies of habitat selection by species at risk provide information for management and recovery programs on critical habitat and are essential for conservation programs to be effective. Many studies on species at risk are conducted in highly altered or degraded habitats because few areas have not experienced human impacts. We investigated habitat selection by Blanding’s turtles (Emydoidea blandingii) in a large protected area, Algonquin Park. Specifically, we evaluated macrohabitat selection at 2 spatial scales (home range and individual location) and microhabitat selection at one scale. Macrohabitat selection was significant at the home range scale but not at the scale of individual location, and no shift in habitat selection was detected among different seasons. Habitat ranks were ambiguous because all wetland types were preferred over lotic and upland habitats. The microhabitat selection data showed no preference for habitat features or shifts among different seasons. These data combined with those from other studies suggest that large study sites in relatively pristine areas may include a large amount of suitable high-quality habitats such that habitat selection at a fine scale may not be detected or multiple habitat types may provide the resources necessary to support populations.Keywords: critical habitat, Emydoidea blandingii, habitat quality, hierarchical selection, home range, spatial scale.

Résumé : Identifier les habitats dans lesquels une espèce est susceptible de se trouver est extrêmement important pour comprendre l’histoire de vie et l’écologie générale de l’espèce. Les études de sélection d’habitats chez les espèces menacées fournissent des informations sur les habitats critiques pour la gestion et les programmes de rétablissement. Ces informations sont essentielles afin que les programmes de conservation soient efficaces. Plusieurs études sur les espèces menacées sont réalisées dans des habitats grandement modifiés ou dégradés par les impacts humains puisque peu de secteurs ont été épargnés. Nous avons examiné la sélection d’habitats chez la tortue mouchetée (Emydoidea blandingii) dans une grande aire protégée, le parc Algonquin. Spécifiquement, nous avons évalué la sélection du macrohabitat à 2 échelles spatiales (le domaine vital et les localisations individuelles) et la sélection du microhabitat à une échelle spatiale. La sélection du macrohabitat était significative à l’échelle du domaine vital, mais ne l’était pas à l’échelle des localisations individuelles et aucun changement dans la sélection d’habitats n’a été observé entre les saisons. Le classement des habitats était ambigu, car tous les types de milieux humides étaient préférés par rapport aux habitats lotiques et en hauteur. Les données de sélection du microhabitat n’ont montré aucune préférence pour des caractéristiques de l’habitat ni de changement entre les saisons. Ces résultats combinés à ceux d’autres d’études sur le sujet suggèrent que des sites d’étude de grande taille dans des aires relativement intactes puissent inclure une grande quantité d’habitats appropriés de qualité élevée. Ainsi, la sélection d’habitats à fine échelle peut ne pas être détectée ou alors les multiples types d’habitats pourraient fournir les ressources nécessaires pour subvenir aux besoins des populations.Mots-clés : domaine vital, échelle spatiale, Emydoidea blandingii, habitat critique, qualité de l’habitat, sélection hiérarchique.

Nomenclature: Ernst & Lovich, 2009.

Introduction

1Rec. 2009-09-29; acc. 2010-01-28. Associate Editor: Patrick Gregory.2Present address: Department of Biology, University of New Brunswick, Saint John, New Brunswick E2L 4L5, Canada.

3Author for correspondence. E-mail: [email protected] 10.2980/17-1-3317

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or fragmented landscapes. In these areas, high-quality habitat may be a limiting resource, or the landscape may be more heterogeneous (Gabor & Hellgren, 2000), with poor-quality habitat isolating limited patches of high-quality habitat. Selection under such conditions would theoretic-ally be highly significant (Boyce & McDonald, 1999). Conversely, in relatively pristine areas, high-quality habitat may not be a limiting resource and the landscape may be homogeneous in terms of meeting the requirements of resi-dent species. Under these conditions, habitat selection may not be detectable (Dasgupta & Alldredge, 2002; Alldredge & Griswold, 2006).

Results of ecological studies are dependent on the scale at which the observation occurs (Wiens, 1989). Using mul-tiple spatial scales accounts for the biology of the study spe-cies while removing the influence of human perception, and thus ensures that results are biologically relevant (Johnson, 1980; Morris, 1987; Aebischer, Robertson & Kenward, 1993; Conner & Plowman, 2001; Alldredge & Griswold, 2006). Using hierarchical theory to study habitat selection reflects how ecosystems are organized and how animals make choices, because selection at one scale is dependent on selection at the scale one level higher in the hierarchy (Johnson, 1980; Schaefer & Messier, 1995). In this frame-work, macrohabitat selection occurs at 3 spatial scales: selection of the population range, selection of an individ-ual’s home range, and selection of locations; these selection scales are referred to as 1st, 2nd, and 3rd order selection, respectively (Johnson, 1980). Habitat selection occurs when habitats are used disproportionately to their availability. Any habitat that is used more than expected is preferred while any habitat used less than expected is avoided (Neu, Byers & Peek, 1974). Presumably, a habitat type is selected because it provides a microhabitat that allows the animal to meet a biological or physiological need (Huey, 1991). Because the biological needs of animals can change among seasons, habitat selection may differ seasonally (Smith, Hupp & Ratti, 1982).

The needs of populations may differ due to regional variation in seasonality. For turtles at the northern periphery of their range, the annual cycle can be divided into 5 distinct periods (Arvisais et al., 2004; Litzgus & Mousseau, 2004): overwintering (late October/early November until April/May), prenesting (April/May until late May), nesting (May/June until late June/early July), summer (late June/early July until late August/early September), and prehibernation (September until late October/early November). There are 3 related biological requirements that must be met by tur-tles during the active period (prenesting through prehiber-nation): individuals need to acquire energy, thermoregulate, and find suitable refuge (Congdon, 1989). Individuals must acquire enough energy to meet the seasonal metabolic demands associated with maintenance, growth, reproduc-tion, and storage (Wiegert, 1968; Congdon, 1989). Because metabolic rate and feeding in ectotherms are directly related to body temperature (Congdon, 1989; Huey, 1991) and habitats are thermally heterogeneous, the body temperature an individual obtains is based on its behaviour and micro-habitat selection (Brown, Brooks & Layfield, 1990; Blouin-Demers & Weatherhead, 2002). Individuals also require

refugia to minimize risk of predation or to provide secure sites for basking and dormancy (Huey, 1991).

We investigated macrohabitat and microhabitat selec-tion by Blanding’s turtles (Emydoidea blandingii), a feder-ally threatened species in Canada (COSEWIC, 2005). We examined macrohabitat selection over 2 y at 2 spatial scales using a method based on Euclidean distances (Conner & Plowman, 2001) and microhabitat selection over 1 y in the relatively pristine landscape of Algonquin Park in Ontario, Canada. The goal of our study was to investigate whether habitats preferred by Blanding’s turtles change during different activity periods. To date, most studies on the Blanding’s turtle have focussed on life-history traits and movement patterns, and few studies have investigated habi-tat use and selection (Ross & Anderson, 1990; Piepgras & Lang, 2000; Joyal, McCollough & Hunter, 2001). We com-pared the results of our study with those from other studies to examine habitat selection by the same species in altered and relatively pristine environments.

Methods

STUDY SITE

The study site is located in the northeast corner of Algonquin Provincial Park, Ontario, Canada (45.9° N, 78.0° W). The 3400-ha site contains 340 ha of wetlands; the remainder is mature mixed forest. All wetlands within the study site were classified into 6 categories using the Canadian National Wetland Classification System (Warner & Rubec, 1997). We created 4 additional habitat categories that were not defined in the Canadian National Wetland Classification System (Table I). Habitats were mapped with ArcGIS 9.2 (ESRI, Redlands, California, USA) using available GIS map layers and spatially referenced ortho-photographs, and ground-truthed with a handheld GPS unit (GPSMap76, Garmin, Kansas City, Kansas, USA).

STUDY ORGANISM

Blanding’s turtles occupy relatively large home ranges compared to other freshwater chelonians (Ross & Anderson, 1990; Rowe & Moll, 1991; Piepgras & Lang, 2000; Joyal, McCollough & Hunter, 2001; Rubin, Warner & Ludwig, 2001). Individuals typically use several activity centres within their home range (Ross & Anderson, 1990; Rowe & Moll, 1991; Joyal, McCollough & Hunter, 2001), with occasional sojourns away from an activity centre (Ross & Anderson, 1990). These movement patterns indicate 2 biologically relevant macrohabitat selection scales: selec-tion of habitats contained within home ranges from habitats within the population range, and selection of the habitat at an occupied location from habitats within the home range; and one relevant microhabitat selection scale: selection of habitat features from within the habitat in which the animal is found.

CAPTURE AND TELEMETRY

During spring (April–May), turtles were captured by hand or using a dip net while researchers waded or paddled a canoe in wetlands known to contain Blanding’s turtles. Upon capture, turtles were individually marked by filing a unique combination of notches into marginal scutes (Cagle,

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1939) and by injecting a passive integrated transponder (PIT tag) subcutaneously into a hind limb. Sex of adult turtles was determined by presence or absence of male second-ary sexual characteristics (concave plastron and tail length; Ernst & Lovich, 2009). Transmitters (Model SI-2F, Holohil, Carp, Ontario, Canada) were affixed to the rear marginal scutes by drilling two small holes and using 20-gauge wire. Individuals were radio-tracked with a Lotek Suretrack STR-1000 receiver (Lotek Engineering Inc., Newmarket, Ontario, Canada) or a Telonics receiver (Telonics, Mesa, Arizona, USA) and a 3-element Yagi antenna (Wildlife Materials International, Murphysboro, Illinois, USA). Tracking occurred at least once every 3 d, with the majority of loca-tions being once every other day. Over both years of study, only individuals that had at least 20 radiolocations were used in analyses. In 2006, 8 individuals (1 male, 7 females) were included, and in 2007, 13 individuals (4 males, 9 females) were included. Six females were radio-tracked in both years but each year was used as an independant sample to maximize our sample size.

We defined activity periods (seasons) based on turtle behaviour. Turtles at our study site emerge from hiberna-tion during the second week of April (Edge et al., 2009), and radio-tracking during the prenesting period began on 16 May 2006 and 26 April 2007. The nesting period began on 28 May in 2006 and 2007 when the first gravid female was detected and ended on 18 June 2006 and 19 June 2007, when the last known female oviposited. Radio-tracking for the summer activity period ended on 29 August of 2006 and 2007.

MOVEMENT PATTERNS

Inter-wetland movements were defined as movements between 2 wetlands that necessitated travel in upland habitat. The number of moves for each individual during each activ-

ity period was counted, and the minimum distance between the 2 wetlands was measured using ArcGIS. Intra-wetland movements were defined as movements within wetlands that did not require travel in upland habitat. The distances between consecutive radio-locations within the same wetland were measured using the HAWTHS Tools (Beyer, 2004) extension in ArcGIS. We tested for differences in the length of inter- and intra-wetland movements among activity periods using a Kruskal–Wallis test. Due to a low sample size of males, we did not test for differences between the sexes within seasons.

Because minimum convex polygons (MCP) may not provide an accurate estimate of habitat use for amphibians and reptiles, annual home ranges and activity period home ranges were estimated using 95% kernels with a smooth-ing factor (h) that resulted in their size being equal to that of a 100% MCP (Row & Blouin-Demers, 2006). This was done by calculating the size of kernels with various values of h. We plotted home range size against h, fitted a line of best fit, and used the equation for the line to calculate the smoothing factor that resulted in the size of the kernel equalling that of the MCP for each turtle. We tested for dif-ferences in home range sizes among activity periods using a Kruskal–Wallis test and for difference in annual home range sizes between sexes using a Mann–Whitney U-test. Because we had a small sample size of males, we did not make com-parisons between the sexes within each season. To ensure there were no differences in the amount of habitat available to each individual, linear regression was used to test for a relationship between the number of locations and the size of both activity period home ranges and annual home ranges.

MACROHABITAT SELECTION

Macrohabitat selection was investigated at 2 biologic-ally relevant scales. The first was selection of home range from within the population range (2nd order), and the second

TABLE I. Definitions used to classify habitats at the study site in Algonquin Provincial Park, Ontario, and the area (ha) each habitat type occu-pies. The first 6 are defined by the Canadian National Wetlands Classification (Warner & Rubec, 1997). The last 4 habitat types were created to include all habitats found at the study site.

Habitat type Definition Area in study site (ha)

Bog Dense layer of peat, with small pools of acidic water. The water table is near the surface; the area is usually covered with mosses, shrubs, and sedges; trees might be present. 12.6 Fen Layer of peat and the water table is near the surface. Soils have a higher nutrient content than bogs; vegetation is dominated by sedges and grasses. 33.5 Swamp Area is covered in trees; water is stagnant or a slow-flowing pool. 5.5 Pond (shallow Includes basins, pools, and ponds; vegetation is submerged and usually consists of floating-leaved plants. 51.1water area) Marsh Can be periodically or permanently flooded; no trees, and the dominant vegetation is emergent. 86.5 Creek Flowing water over a mineral or organic substrate with a channel breadth no more than 3 m. 40.7 Ephemeral pool Pools that periodically hold water during the year and are hydrologically connected to a creek. 0.1 Lake Large bodies of water > 50 ha in size. Maximum water depth exceeds 5 m; may have a mineral or organic substrate. Surface vegetation is confined to bays and inlets. 58.3 River Flowing water with a channel breath > 3 m. 48.4 Upland Terrestrial habitats not associated with standing water. 3077


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was selection of locations from within the home range (3rd order). Analyses at both scales were done using the distance-based approach (Conner & Plowman, 2001). The population range (1st order) was defined as a 100% MCP around all turtle locations buffered by 200 m (Figure 1). The buffer was applied so that the population range encompassed the limits of all home ranges. Home ranges (2nd order) were defined as 95% kernels around all loca-tions for each animal. Locations (3rd order) were defined as all radio-locations for each animal.

To investigate habitat selection, 3408 points (referred to as random points) were created in a 100-m uniform pattern across the population range using ArcGIS. Using this pat-tern, the average distance from point to habitat was stable. The distance from random points and telemetry points to the nearest representative of each habitat was measured using Near Tool in ArcGIS. Availability of each habitat was

represented by the mean of the distances from the points one level up in the hierarchy to the nearest representative of each habitat type (ri), and habitat use was the mean distance from the points contained within the selection scale to the nearest representative of each habitat type (ui) for each ani-mal (Conner & Plowman, 2001). For each selection scale, a vector of ratios (d) was calculated for each animal by divid-ing each element of habitat use (ui) by the corresponding element of available habitat (ri). The expected value of the vector ratio (d = ui /ri) for random habitat use is 1 (Conner & Plowman, 2001). The 1st order was all random points within the population range, the 2nd order was all random points within the home range of an individual, and the 3rd order was the telemetry points for each individual. The mean number of random points within home ranges was 63 (range 25–157), and the mean number of radio-locations for each individual was 44 (range 23–54).

FIGURE 1. Map of study area used for the assessment of macrohabitat selection by Blanding’s turtles (Emydoidea blandingii) in Algonquin Provincial Park, Ontario. Population range is a minimum convex polygon around all turtle locations during the 2006 and 2007 active seasons (April–September) buff-ered by 200 m.


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A factorial multivariate analysis of variance (MAN-OVA) was used to test if habitats were used disproportion-ately to availability (d ≠ 1) among seasons. If no significant activity period effect was detected, then the analysis was repeated with annual home ranges. If habitats were used non-randomly, then 2-tailed t-tests were used to test which habitats were preferred, and to produce a relative rank of preference. Comparisons were drawn between spatial scales to determine at what scale selection was significant, and if habitat selection differed between scales.

MICROHABITAT SELECTION

At each turtle location, a 1-m2 plot was positioned with the turtle in the centre and variables were measured, counted, or characterized within the plot to estimate microhabitat use. To estimate microhabitat availability, the same variables were measured in a plot located within the same macro-habitat at a random compass bearing and random distance (10–50 m) away (values were determined a priori using a random number generator).

A total of 9 habitat variables associated with structure or temperature were measured in each plot. Water depth was measured to the nearest centimetre using a metre stick at 5 locations within the plot, at the centre and 50 cm away in each of the cardinal directions. Substrate depth was meas-ured to the nearest centimetre at the same 5 locations as water depth by placing a 3.5-kg brick on top of the measur-ing stick until the stick would not penetrate the substrate any further. Only one brick was used in all cases. Vegetation cover was visually estimated by looking through a 10-cm piece of PVC pipe with a diameter of 3.5 cm at 5 locations within the plot. The percentages of the opening in the PVC pipe covered by submergent, surface, and emergent vegeta-tion, and total cover from 0–50 cm above surface, were esti-mated independently of one another. Water temperature was measured 5 cm below the surface using a digital thermometer (± 1 °C) and at 50 cm below surface using an alcohol therm-ometer (± 2 °C). Air temperature was measured, in shade, 5 cm above the surface using a digital thermometer (± 1 °C).

We used a correlation analysis to test whether variables changed over time (i.e., seasonal changes in water temper-ature and vegetation growth); the turtle and random plots were analyzed separately. For each of the 3 activity periods, a MANOVA was performed to test if the turtle plots and random plots differed from one another. If the plots differed, a Discriminant Function Analysis (DFA) was performed to determine which variables discriminated between turtle and random plots.

The assumption of normality was tested using the Shapiro–Wilks test, and homogeneity of variance was tested

using Levene’s test. All percentage data were Arc Sin square root transformed to meet assumptions of normality and independence. All statistics were performed using Statistica (StatSoft, Tulsa, Oklahoma, USA).

Results

MOVEMENT PATTERNS

There was no signif icant relationship between the number of locations and activity period home range size during the prenesting (r2 = 0.12; df = 8; P = 0.32) and sum-mer periods (r2 = 0.0007; df = 18; P = 0.91), indicating that all individuals had access to the same amount of habi-tat during these seasons. During the nesting period, there was a relationship between the number of radio-locations and activity period home range size (r2 = 0.35; df = 16; P = 0.008), and this relationship was driven by 1 female that occupied a nesting home range (168.91 ha) twice the size of all other females; therefore, she was removed from the analysis. Her large home range was due to a long nest-ing migration (> 6000 m). This is the largest known nesting migration at our study site, and we do not have evidence to suggest movements of this length are common at our study site. With the remaining 16 individuals, there was no relationship between the number of radio-locations and activity period home range size (r2 = 0.047; df = 15; P = 0.40), indicating that all individuals had access to the same amount of habitat during the nesting season. Furthermore, when the habitat selection analyses were per-formed with and without this female, the results were the same. Using the 16 individuals, there were no significant differences in home range sizes during different activity periods (χ2 = 1.33; df = 2; P = 0.51; Table II). Seasonal home range size was stable when there were at least 7 radio-locations per individual. There was no relationship between annual home range size and the number of radio-locations (r2 = 0.016; df = 19; P = 0.58). There was no dif-ference between the mean annual home range size of males (n = 5) and females (n = 16) (U = 39; df = 1; P = 0.93; Table II). Annual home range size was stable when there were at least 20 radio-locations per individual.

The mean number of inter-wetland movements for both sexes was 4. There was no difference in the length of inter-wetland movements during any of the activity periods (χ2 = 0.89; df = 2; P = 0.64; Table II). On average, females moved greater distances between wetlands than males, but due to a high level of variability, this difference does not appear to be significant. The majority of inter-wetland movements (81%) were less than 500 m in length, but 6 movements by females were greater than 2000 m in length

TABLE II. Mean home range size and distance of inter-wetland and intra-wetland movements (± SD) by activity period (Season) for male (n = 5) and female (n = 16) Blanding’s turtles (Emydoidea blandingii) in Algonquin Provincial Park, Ontario.

Season Home range (ha) Inter-wetland movement (m) Intra-wetland movement (m)

Male Female Male Female Male Female

Prenesting 41.4 ± 16.6 30.1 ± 21.3 188 ± 111 702 ± 843 104.6 ± 53.2 73.2 ± 51.5Nesting 22.5 ± 9.5 40.7 ± 39.4 275 ± 0 522 ± 684 136.9 ± 64.6 173.7 ± 197.3Summer 46.1 ± 12.9 33.2 ± 46.7 247 ± 78 373 ± 836 66.6 ± 43.8 88.4 ± 28.6Annual 57.1 ± 15.3 61.2 ± 30.4 231 ± 89 497 ± 731 83.5 ± 39.9 91.0 ± 37.4


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(Figure 2); all of these occurred during the nesting period. For intra-wetland movements, there were no differences in mean distances between subsequent radio-locations among activity periods (χ2 = 4.10; df = 2; P = 0.13; Table II).


Habitat selection was significant only at the scale of the home range (2nd order). For 2nd order selection, the dis-tances from random points within home ranges to habitats differed from the distances to habitats from random points within the population range (F10, 11 = 14.41; P < 0.05). There was no significant interaction between activity period and home range selection (F20, 74 = 0.062; P = 1.00). The only habitat with a mean vector ratio value greater than 1 was upland habitat, which indicates that all aquatic habitats were preferred over upland habitat. Two-tailed t-tests cat-egorized the habitats into 3 groupings (Table III). The most preferred habitats were swamp, pond, marsh, lake, fen, and bog, which were significantly preferred over river, creek, and ephemeral pool, which were significantly preferred over upland habitat. For 3rd order selection, there were no differ-

ences between the observed distances from radio-locations to habitats and the distances from random points to habitats within home ranges (F9, 9 = 0.71; P = 0.69) and there were no differences among activity periods (F20, 74 = 0.0971; P = 1.00), indicating that habitat selection did not occur at the 3rd order spatial scale.


From 24 April 2007 until 29 August 2007, 19 indi-vidual Blanding’s turtles (11 females, 8 males) were radio tracked, for a total of 381 turtle plots and 236 random plots with complete data sets for structure and temperature vari-ables. The majority of these variables changed over time and the relationship appeared to be linear, but there was a large amount of variability in the measured values. The relatively low r2 values for the regressions indicate that the relationships may not be biologically relevant (Table IV). Of interest are the variables that differ in turtle plots com-pared to random plots over time. Vegetation from 0 to 50 cm increased over time in random plots (r2 = 0.0072; df = 234; P = 0.045) while staying constant in turtle plots (r2 = 0.0012; df = 379; P = 0.41). Submergent vegeta-tion in random plots was constant over time (r2 = 0.0054; df = 234; P = 0.13) and decreased in turtle plots (r2 = 0.016; df = 379; P = 0.0043). Lastly, water depth was constant over time in random plots (r2 = 0.0009; df = 234; P = 0.55) and decreased in turtle plots (r2 = 0.013; df = 379; P = 0.0091).

During the prenesting period, 13 turtles (8 females, 5 males) were radio tracked. There were 35 turtle and 23 random plots with complete structure and temperature data sets. There were no differences between turtle and random plots with respect to any of the microhabitat vari-ables (λ = 0.84; F9, 48 = 1.02; P = 0.44). During the nesting period, 15 turtles (10 females, 5 males) were radio tracked. There were 66 turtle and 51 random plots with complete structure and temperature data sets. There were no differen-ces in temperature or structure variables between turtle and random plots (λ = 0.94; F9, 107 = 0.73; P = 0.68). During the summer period, 18 individuals (11 females, 7 males) were radio tracked. There were 280 turtle and 162 random plots with complete temperature and structure data sets. There were differences in temperature and structure variables between turtle and random plots (λ = 0.93; F9, 432 = 3.78; P < 0.005). The squared Mahalanobis distance between tur-tle and random centroids was 0.34 (P < 0.005). The standard

FIGURE 2. Histogram of the number of inter-wetland movements (n = 86) by 21 (16 female, 5 male) Blanding’s turtles (Emydoidea bland-ingii) during the 2006 and 2007 active seasons. Of the 86 total movements, 80 movements (93% of total) were < 2000 m in length, 76 movements (88% of total) were < 1000 m in length, and 70 movements (81% of total) were < 500 m in length.

TABLE III. Vector ratios (d) and P-values from two-tailed t-tests for 2nd order distance-based habitat selection by Blanding’s turtles (Emydoi-dea blandingii) in Algonquin Provincial Park, Ontario. Significant values (P < 0.05) reported here, shown in bold, indicate where significant selection occurred.

d Swamp Pond Marsh Lake Fen Bog River Creek Ephemeral (ui / ri) pool

Swamp 0.368 Pond 0.422 0.595 Marsh 0.424 0.390 0.989 Lake 0.466 0.449 0.781 0.756 Fen 0.524 0.422 0.634 0.614 0.799 Bog 0.562 0.234 0.451 0.409 0.632 0.876 River 0.686 < 0.05 0.132 0.937 0.251 0.497 0.563 Creek 0.687 < 0.05 < 0.05 < 0.05 0.185 0.456 0.515 0.993 Ephemeral pool 0.704 < 0.05 < 0.05 < 0.05 0.127 0.397 0.438 0.917 0.908Upland 3.521 < 0.05 < 0.05 < 0.05 < 0.05 < 0.05 < 0.05 < 0.05 < 0.05 < 0.05


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coefficients indicate that emergent vegetation and water depth were the largest contributors to the first discriminant function (Table V). The DFA correctly classified 70% of all plots as turtle or random (93% of turtle plots and 32% of random plots).

Discussion

MOVEMENT PATTERNS

Blanding’s turtles moved extensively between and with-in wetlands. The large and frequent inter-wetland move-ments observed in our study and reported elsewhere (Ross & Anderson, 1990; Row & Moll, 1991; Piepgras & Lang, 2000; Joyal, McCollough & Hunter, 2001) indicate that upland habitat is not a barrier to movements by Blanding’s turtles. Individuals travel extensively between wetlands dur-ing all seasons. Individuals can traverse their entire home range in a matter of days, as shown by the long and rapid nesting migrations undertaken by some females (Congdon et al., 1983; Standing, Herman & Morrison, 1999; this study). In addition, we observed some males to spend up to a week traveling from overwintering locations to summer wetlands. Intra-wetland travel was also extensive and occa-sionally covered great distances. As a result of these move-ment patterns, all habitats within an individual’s home range were available at any point in time.

Movements between wetlands are thought to be induced by wetland drying (Rubin, Warner & Ludwig, 2001), chan-ges in food availability (Ross & Anderson, 1990), thermal quality of the wetland (Sajwaj & Lang, 2000; Hartwig &

Kiviat, 2007), and efforts to facilitate nesting and repro-duction (Congdon et al., 1983; Ross & Anderson, 1990; Joyal, McCollough & Hunter, 2001). During our study, all wetlands used by Blanding’s turtles held water for the entire year; thus, it is unlikely that wetland drying caused individ-uals to move between wetlands. Interestingly, females did not make more inter-wetland movements during the nesting period, in contrast to observations reported elsewhere for Blanding’s turtles (Piepgras & Lang, 2000). The average length of inter-wetland movements by females was 247 m greater than that of males, and some females made con-siderable nesting migrations (> 6000 m in one case). We did not test for differences in inter-wetland movements between the sexes within activity periods due to a small sample size for males, but the high amount of variability in the data indicates that any differences are unlikely to be significant. An increase in the number of inter-wetland movements by females would be expected if suitable nest sites were lim-ited. Gravel roads (Standing, Herman & Morrison, 1999; Congdon et al., 2000) and human-altered areas (Joyal, McCollough & Hunter, 2001) are used by Blanding’s turtles as oviposition sites. At our study site, a forest access gravel road presented 10 km of suitable nesting habitat, which was used by multiple individuals, and it is unlikely that suitable nesting habitat is a limiting resource.


For Blanding’s turtles in Algonquin Park, biologic-ally significant macrohabitat selection occurred at the home range scale but not at the individual location scale. Upland habitat was the only habitat avoided; however, it was used as a travel corridor between wetlands and for nesting. Upland habitat can also be used for late season aestivation in this species (Joyal, McCollough & Hunter, 2001), but aestiva-tion is rare in reptiles living at northern latitudes (Litzgus & Brooks, 2000) and was never observed during our study. It is unlikely that upland habitat provides sufficient foraging opportunities or refuge as the diet of Blanding’s turtles is largely composed of aquatic invertebrates, amphibian lar-vae, vegetation, and small fish (Sajwaj & Lang, 2000; Edge, 2008; Ernst & Lovich, 2009). Management should consider how these animals use the landscape, and provide protection at the level of the home range and not simply at the scale of preferred individual wetlands.

TABLE IV. Correlation values for structure and temperature variables and Julian date measured at Blanding’s turtle (Emydoidea blandin-gii) locations and in random plots. P-values in bold indicate signifi-cant correlations at P < 0.05.

Microhabitat Plot Direction of r2 P-valuevariable type relationship

Vegetation from Location 0.0012 0.41 0–50 cm Random + 0.0072 0.045 Surface vegetation Location + 0.066 < 0.001 Random + 0.081 < 0.001 Emergent vegetation Location + 0.024 < 0.001 Random + 0.028 < 0.001 Submergent Location – 0.016 0.0043 vegetation Random 0.0054 0.13 Water depth Location – 0.013 0.0091 Random 0.0009 0.55 Substrate depth Location + 0.009 0.03 Random + 0.0011 0.032 Air temperature Location + 0.068 < 0.001 Random + 0.066 < 0.001 Surface water Location + 0.081 < 0.001 temperature Random + 0.079 < 0.001 50-cm water Location + 0.024 0.0012 temperature Random + 0.032 0.001

TABLE V. Standardized coefficients for canonical roots of 9 habi-tat structure and temperature variables used in the assessment of microhabitat selection by Blanding’s turtles (Emydoidea blandingii) during the summer period in Algonquin Provincial Park, Ontario. Large standardized coefficients values indicate variables with high discriminatory power.

Microhabitat variable Standardized coefficients

Vegetation from 0–50 cm –1.55Surface vegetation –0.18Emergent vegetation 1.44Submergent vegetation 0.12Water depth 0.64Substrate depth –0.19Air temperature 0.22Surface water temperature 0.05750-cm water temperature –0.22


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There were no differences in habitat selection at either scale among activity periods, indicating that Blanding’s tur-tles do not select different habitat types seasonally. Spotted turtles (Clemmys guttata) shift among habitats to meet different biological or behavioural needs related to mating and thermoregulation (Litzgus & Brooks, 2000; Litzgus & Mousseau, 2004). Wood turtles (Glyptemys insculpta) are found in or near aquatic habitats in early spring and late summer to thermoregulate and hydrate (Arvisais et al., 2004) and shift into upland habitat during the later spring and early summer to forage (Arvisais et al., 2004; Greaves, 2007). Unlike spotted and wood turtles, Blanding’s turtles did not have different habitat requirements during early and late portions of the active season, possibly due to differ-ences in mating and overwintering requirements. Spotted turtles aggregate in spring for mating (Ernst, 1967; Litzgus & Brooks, 2000; Litzgus & Mousseau, 2004), whereas the majority of mating in Blanding’s turtles occurs just prior to and after hibernation (Edge et al., 2009; Newton & Herman, 2009). Wood turtles spend the majority of the summer on land, returning to rivers to hibernate (Compton, Rhymer & McCollough, 2002; Arvisais et al., 2004; Greaves, 2007), whereas Blanding’s turtles use upland habitat as a travel cor-ridor between wetlands and overwinter in wetlands that are used during the active season (Edge et al., 2009). Habitat selection may also differ between the sexes; for example, females nest in upland habitat, while males do not require upland habitat to meet reproductive needs. The low sample size of males in our study precluded the statistical investiga-tion of differences between the sexes.


We did not detect microhabitat selection during the prenesting or nesting period, but during the summer period, water depth and emergent vegetation discriminated between turtle and random locations. Selection for specific habitat variables occurs when individual animals select habitat features that are not available ubiquitously in the environ-

ment (Gabor & Hellgren, 2000). It has been suggested that chronological habitat use in turtles reflects seasonal chan-ges in vegetation and temperature (Kaufmann, 1992). As temperatures increase and vegetation changes, new habitats become accessible, and individuals will exploit resources as they become available.

IMPLICATIONS AND CONCLUSIONS

Selection for particular habitats can be dramatically altered by habitat modification and destruction (Arthur et al., 1996; Schaefer & Mahoney, 2007), because animals may use less-productive foraging habitats in areas with high levels of disturbance (Allen, 2000). At our relatively pristine site, we found evidence for habitat selection by Blanding’s turtles at the scale of the home range and not the location of an individual, contrasting with the results of other studies. Other studies have reported significant habitat selection by Blanding’s turtles (Kofron & Schrieber, 1985; Ross & Anderson, 1990; Power, Herman & Kerekes, 1994; Rubin, Warner & Ludwig, 2001; Hartwig & Kiviat, 2007) in habi-tats impacted by human activities. When making compari-sons between our study and others, consideration should be paid to 2 components. If the study site is large and relatively pristine (as is the case in Algonquin Park), then all habi-tats are likely represented in sufficient amounts; therefore, selection may not be detectable because no preferred habi-tat is a limiting resource. An example of this is presented in Figure 3. In Figure 3a, habitat 1 is a limiting resource, while in Figure 3b, habitat 1 is not a limiting resource; in both figures there are 20 hypothetical animal locations that represent habitat use. The use of habitat 1 does not increase as the availability of habitat 1 is increased, and under this condition, selection for habitat 1 may not be detected. If selection is detected, an investigator should consider if pre-ferred habitats are rare habitats, and if avoided habitats are common habitats (Mysterud & Ims, 1998), because the use of habitats reflects the quality and abundance of resources within them (Boyce & McDonald, 1999).

FIGURE 3. Theoretical example of habitat selection in a landscape where habitat 1 is a limited resource (a) and in a landscape where habitat 1 is not a limited resource (b). In both cases, usage (# of animal locations) of habitats 1 and 2 is not different (i.e., 15 locations in habitat 1 and 5 locations in habitat 2). When the availability of habitat 1 is increased (a versus b), usage of habitat 1 does not increase. In a, selection for habitat 1 would be detected, while in b, selection for either habitat would not be detected.


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Potential differences in the quantity and quality of available habitats are apparent in studies investigating habi-tat selection by Blanding’s turtles. In Wisconsin, Blanding’s turtles used ponds more frequently than marshes (Ross & Anderson, 1990), but the authors note that individuals seemed to use open water preferentially, regardless of habi-tat type. Open water may represent a limiting resource at the Wisconsin study site. In Illinois, Blanding’s turtles used artificial ponds more frequently than natural wetlands as the wetlands became scarce due to drying (Rubin, Warner & Ludwig, 2001); as preferred habitat became scarce, individuals began to use marginal habitat more frequently. The Wisconsin and Illinois studies were conducted in for-est reserves located in urban or developed areas. Habitat selection has also been examined in much smaller study areas: A 7.4-ha constructed site bordering a high school in New York (Hartwig & Kiviat, 2007), and the only remain-ing pond (1.4 ha) known to contain Blanding’s turtles in Missouri (Kofron & Schrieber, 1985). These 2 study sites are likely highly modified or degraded. The authors do not describe the habitat between wetlands; if that habitat pre-sents a barrier to movement, individuals would not be able to move to different habitats. Therefore, selection may have been found not because the used habitats are preferred, but because individuals were unable to move to other habitats. Another study that reports habitat selection by Blanding’s turtles is in a large national park in Nova Scotia. This population has been the focus of a long-term mark–recap-ture project (Herman, Power & Eaton, 1995; McMaster & Herman, 2000; Mockford et al., 2005). The turtles in Nova Scotia are closely associated with darkly coloured water (Power, Herman & Kerekes, 1994), but to our knowledge, no macrohabitat selection model has been published for this population.

In Algonquin Park, active forest management occurs within the park boundaries, but the study site has not been logged in the last 20 y and the upland habitat is largely mature mixed forest. The study site is large (3400 ha), with 340 ha of wetlands, a landscape that is dramatically differ-ent from the landscape found in other study sites (besides the one in Nova Scotia). No habitat within the Algonquin Park study site is likely a limiting resource, and all wetland habitats may present similar structure and feeding opportun-ities for turtles. When comparing these studies, we assumed that habitat use in each is representative of all animals at all times. There are several factors that may violate this assumption. Major differences include analyses, study dur-ation, study location, and local environmental conditions. Further work should be undertaken using several popula-tions living in landscapes with varying levels of disturbance or disruption to directly investigate whether habitat selec-tion changes under different levels of disturbance.

Acknowledgements

Funding for this research came from the Natural Sciences and Engineering Research Council of Canada (NSERC) (sep-arate grants to J. D. Litzgus and R. J. Brooks), World Wildlife Fund-Endangered Species Recovery Fund (WWF-ESRF) and Environment Canada (to C. B. Edge and J. D. Litzgus), Ontario Parks, the Algonquin Forest Authority (to B. D. Steinberg), the Friends of Algonquin Park (to B. D. Steinberg), the Toronto

Zoo (to C. B. Edge, J. D. Litzgus, and R. J. Brooks), and Swish Maintenance Limited (to B. D. Steinberg). We would like to thank K. Mulligan, R. Dolson, and volunteers who made this study pos-sible and the staff at Achray campground for their hospitality. The study was carried out under the guidelines of the Canadian Council on Animal Care and the Laurentian University Animal Care Committee (protocol no. 2004-11-01).

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Habitat Selection by Blanding's Turtles ( Emydoidea blandingii ) in a Relatively Pristine Landscape