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Varied tastes: Home range implications of foraging-patch selection
Abstract
Despite evidence of home range behaviour across many taxa, the mechanisms underlying the development of home ranges are still unknown. Recently, models have been developed to explore these mechanisms for both territorial and non- territorial species. One such model for a generic forager suggests animal memory and optimal foraging theory as underlying mechanisms driving forager movement and the development of stable home ranges. Although this is a promising model for ungulate home range development, assumptions of the model have yet to be evaluated. Using GPS relocation data from two populations of elk, we explored how foraging patch selection might influence the structure and development of home ranges in elk Cervus elaphus. During the summer growing season, we identified and sampled foraging patches used by elk. Points along elk paths not used for foraging were sampled identically for comparison. We contrasted ‘patch’ and ‘nonpatch’ data points, to identify foraging selection differences across herd, sex and season using a combination of directly sampled and remotely sensed covariates. In general, elk selected patches with higher biomass, cover, slope and lower traffic on the nearest road. These patch-selection results speak directly to differences between foraging areas and other areas used by elk and demonstrate that both physiographic and anthropocentric features influence foraging patch selection. Our results offer insight as to what defines a valuable foraging patch for elk and how these patches might influence the development and structure of home ranges in a free-ranging ungulate.
Supplementary resource (1)
... Optimal foragers that rely on regularly replenished food sources commonly visit feeding sites in stable sequences, termed traplining, to maximise resource renewal rates and minimise travel distances (Gill 1988;Ohashi & Thomson 2009;Kays et al. 2012;Lihoreau et al. 2013). Foragers tend to select patches or prey based on energy maximisation (Sims & Quayle 1998;Robakiewicz & Daigle 2004;Brose 2010;Bleicher & Dickman 2016;Mahenya et al. 2016;Seidel & Boyce 2016), palatability (Mahenya et al. 2016), or macronutrient composition (Kohl, Coogan & Raubenheimer 2015), but also monitor local patches of lower quality to enable patch switching should conditions change (Smith & Sweatman 1974;Wildhaber & Crowder 1991;Dall & Johnstone 2002;Spencer 2012). ...
... To forage efficiently, animals should select the highest quality patches, based on a combination of food availability, habitat attributes and predation risk (e.g. Wei et al. 2015;Seidel & Boyce 2016) and typically restrict food searching movements within a home range to maintain an updated 'cognitive map' of local resources Spencer 2012). However, foragers occasionally travel considerable distances outside their territories to exploit desirable food resources, e.g. ...
The red fox (Vulpes vulpes) is a contentious species of global importance as a predator, competitor, vector of disease and pest. Understanding their social system is essential for successful species management and mitigating human-wildlife conflict. Foxes are solitary foragers that form groups in certain circumstances. It is unclear whether these groups are beneficial or simply the ‘best of a bad job’ due to ecological constraints. Further, little is known about how stable or cohesive fox groups are, which can have implications for disturbance or removal. I addressed these issues to further our understanding of how fox groups operate.
I set up camera traps in residential gardens where foxes were fed (food patches), to study social and competitive relationships in the high density fox population of suburban Bristol, UK. I collected over 152,000 photos of foxes and identified 192 individuals.
Social groups were difficult to define, but the most reliable definition encompassed shared space use, a sighting threshold and the number of social connections. Group membership was relatively stable; foxes associated in communities, mainly within their territory boundary and maintained long term relationships that lasted until death or emigration. However, in all seasons the majority of relationships lasted less than a day and were probably between foxes from different social groups, indicating that intergroup contacts were not uncommon and occurred year round.
Food patches were hotspots for sociality. Foxes improved their foraging efficiency by selecting high quality patches and coinciding their foraging activity with anticipated food availability, which increased contact rates at high quality patches. Females foraged according to their seasonal energetic demands, while males reduced their foraging effort in the winter mating season in favour of mate-searching behaviour. This contributed to a significant alteration in social structure in winter, with an increased rate of territory intrusion by strangers, a greater proportion of short term relationships and reduced social connectivity, demonstrating a role of females in maintaining group cohesion in winter.
Dominant foxes occupied central network positions and therefore had a major influence on group connectedness; the demise of a dominant male led to significant social perturbation in one territory, supporting the importance of breeders in canid groups. Dominance also facilitated priority access to food, but so too did resident group membership, perhaps through familiarity with local resources and conspecifics. Subordinates compensated for intragroup competition by utilising lower quality patches and risky extraterritorial foraging, which was observed at an unexpectedly high rate year round. Contrary to the resource dispersion hypothesis, this indicated that group size was not limited by within-territory resources.
To my knowledge, this is the most detailed study of fox sociality to date. Despite low contact rates fox groups were relatively stable and more similar in complexity to other canids than previously acknowledged. High individual flexibility in space use and year-round extraterritorial movement may have functioned to mitigate competition, but also explained how foxes responded so rapidly to local demographic change, providing evidence for the futility of management by removal.
... Porcupine Hills is predominantly mixed and shortgrass prairie, possibly forcing elk to travel farther from forest cover to find adequate forage. In contrast, Turtle Mountain is heavily forested and intermixed with cropland, potentially reducing the necessary travel distance from security cover [21]. Vegetation and landscape differences [2] between our study areas may explain differences in size of home range among all 3 elk herds [57] [58]. ...
... Home range size increased during winter and at night. During winter, reduced habitat quality due to snow and cold temperatures may have forced elk to travel farther to seek adequate forage and cover [21]. We expected our study elk to display larger home ranges at night, given elk are known to rest and forage in cover throughout the day and forage in more open areas at night [59]. ...
Changes in land use have resulted in range shifts of many wildlife species, including those entering novel environments, resulting in the critical need to understand their spatial ecology to inform ecosystem effects and management decisions. Dispersing elk (Cervus elaphus) were colonizing areas of suitable habitat in the Northern Great Plains, USA, resulting in crop depredation complaints in these areas. Although state resource managers had little information on these elk herds, limited evidence suggested temporal movements into Canada. We collected and analyzed essential information on home range and habitat selection for 3 elk herds residing in North Dakota. We captured 5 adult female elk in each study area, affixed global positioning system collars, and monitored them for 1 year (2016–2017). We estimated diel period, seasonal, and hunting season home ranges using Brownian Bridge Movement Models for each individual. We analyzed habitat selection using multinomial logit models to test for differences in use of land classes, and for departures from proportionate use based on random sampling; our predictor variables included individual elk, diel period, and season. Home ranges differed between the 3 herds, seasons, and diel period; gun and winter season home ranges were both larger than in summer, as was night when compared with day. Female elk generally restricted themselves to cover during the day and entered open areas at night and during winter months. Our results also suggest that elk in our study areas tended to seek more cover, and in the case of our Turtle Mountain study area, some cross into Canada during gun season. Our study provides a better understanding of the spatial ecology of elk in the Northern Great Plains while highlighting the need for enhanced international cooperative management efforts.
... How much greater? According to optimal foraging theory (MacArthur & Pianka, 1966;Schoener, 1971;Maurer, 1996), it should be at least large enough to yield an adequate food supply to satisfy the body needs during a given period (Andersson, 1978;Schoener, 1983;Seidel & Boyce, 2016). Thus, it must be greater in the sex with bigger body size according to terrestrial movement energetics and its application to the optimising animal (Halsey, 2016). ...
... Besides the legume availability effect on the size of morning foraging area, there could be a food distribution effect on animal mobility. Where food is patchily distributed the individual would have to move between more patches and thus increases its foraging area (Tufto et al., 1996;Haskell et al., 2002;Säid et al., 2005;Seidel & Boyce, 2016). Here we did not evaluate the effect of spatial distribution of legume fields on MFA sizes because legume fields were aggregated according to an agri-environmental scheme (Ponce et al., 2014 and own unpub. ...
Sexual size dimorphism (SSD) may favour physiological peculiarities in diet, behaviour and home-range size both across species and within species. Sex-specific differences in diet and behaviour have been reported in several bird species but there are fewer studies of foraging area size in sexually dimorphic bird species. Foraging area size should be greater in the bigger sex according to home-range size predictions based on body mass. We tested this prediction in a winter study of foraging area size in the Great Bustard Otis tarda , the most sexually size-dimorphic bird species, which forages in unisexual flocks. In this species the temporal pattern of a flock's feeding intensity; the proportion of birds actively feeding (FI) and the size of the morning foraging area (MFA) of each sex are unknown. We recorded the behaviour and movements of unisexual flocks of Great Bustards during winter mornings and sampled food availability to take into account its effect on FI and MFA. FI increased and then decreased through the morning in both sexes, and was lower in males than in females. This sexual difference was greater where legume availability was smaller. Legumes were the most preferred substrate type. Consequently, MFA sizes were smaller in sites with more legume availability. We did not find sexual differences either in the size of MFA or in the selection of the two preferred substrate types: legumes and stubble fields. MFA and FI were determined to a greater extent by ecological factors such as food availability than by metabolic requirements derived from body size differences. These results obtained from a short-term study do not preclude an effect of sexual size dimorphism on MFA size and FI of Great Bustards over longer periods but show that the body size effect on foraging behaviour may be smaller than predicted only by SSD.
... The seasonal home ranges of the suckler cows were also similar to the summer home ranges of certain wild herbivores. This includes the females of European bison (Bison bonasus) (Krasińska et al., 2000) and elk (Cervus canadensis) (Seidel and Boyce, 2016) in forested habitats of Poland/Belarus and Alberta, respectively. Bjørneraas et al. (2012) found that the summer home ranges of female moose, both with and without calves, in similar habitats in Norway were 500 ha and 400 ha, respectively. ...
... First, elk home ranges would be largely forested because the Pennsylvania Elk Management Area (EMA) is dominated by forest cover. However, because elk are intermediate grazers, seasonal space use would be driven by access to herbaceous forage throughout the year (Anderson et al. 2005;Seidel and Boyce 2016;Amor et al. 2019). Second, we expected that seasonal space use would be larger and more variable for males than for females (Rosatte 2017). ...
Home ranges are vitally important to an animal's behavior, survival, and reproduction. Variation in environmental conditions and landscape composition coupled with differences between sexes can influence home range structure, and understanding these differences is important for species management. Elk (Cervus canadensisErxleben, 1777) are a widespread culturally important ungulate that has been well studied over portions of its range. Reintroduced populations in eastern North America, where conditions differ dramatically from those in the west, are comparatively understudied. Using Ornstein–Uhlenbeck movement models, we calculated season- and sex-specific home range and core areas for elk in Pennsylvania, USA. Results showed strong seasonal variation in sizes of core areas and home ranges, with summer ranges consistently smaller than other seasons. Home ranges were largely forested. However, forest cover of core areas was lower than home ranges. Proportion of open cover types was greater in core areas than home ranges. Use of timber harvests overall was low. However, among individuals with highly forested home ranges, timber harvests were strongly selected for in spring. This work highlights the regional specificity in the size, composition, and seasonality of elk home ranges, and stresses the need for additional context-specific research in understudied elk populations of forested eastern landscapes.
... Furthermore, the arrangement of the home ranges of females to those of males has been used as a proxy for mating systems (Geffen and MacDonald 1992;Park et al. 2019). Nevertheless, such approaches are based only on the spatial shape and positioning of home ranges in space, with few studies (Edworthy et al. 2012;Seidel and Boyce 2016;Ofstad et al. 2019) considering ecological components of the environment that might play a role in constraining or promoting behavioral interactions that define individuals' dispersion in a population. ...
In many species, the shape, size, and location of home ranges depend on the spatial positioning of resources. Therefore, evaluating the resources and conditions related to the space use of individuals can provide crucial information on the species’ ecology and sociobiology. In this study, we evaluated factors shaping the use of space by the lizard Tropidurus montanus M.T. Rodrigues, 1987 and assessed how the distribution of resources can affect the size of the home range and how the quality of the male's home range can influence the number of associated females. We hypothesized that (i) males with a larger body size would have a higher-quality home range, and (ii) there would be a positive relationship between the home-range size and home-range quality of males and the number of associated females. Our results suggest that males, females, and juveniles adopt different strategies. While females and juveniles have relatively small home ranges located in more suitable locations, males invest in larger home ranges, including in lower-quality habitat patches. Our results suggest that males increase their home ranges to incorporate resources females prefer, enlarging the number of females in their harems.
... These pairs of predictor value sets form the basis of the conditional logistic regression. 4 We fitted the following conditional logistic regression selection model (response variable w, predictors x 1 to x n , and selection ratios β i , i = 1, ...n,-β i < 0 indicates selection against the i th predictor variable) [53,54] so that we could relate the set of values x n arising from each 'used' area with a response value w T in the associated 'available' area [55][56][57], where we used T to refer to the year of the particular data set used. 5 We included individual ID as a random effect [58,59] variable in our model alongside our fixed effects of Greenness ( x 1 ), Wetness ( x 2 ) , Road Density ( x 3 ), and Anthrax Risk ( x 4 ). We repeated this analysis separately for each of the two seasons, thereby deriving w 2009 and w 2010 as separate step selection functions (SSFs). ...
Movement behavior is an important contributor to habitat selection and its incorporation in disease risk models has been somewhat neglected. The habitat preferences of host individuals affect their probability of exposure to pathogens. If preference behavior can be incorporated in ecological niche models (ENMs) when data on pathogen distributions are available, then variation in such behavior may dramatically impact exposure risk. Here we use data from the anthrax endemic system of Etosha National Park, Namibia, to demonstrate how integrating inferred movement behavior alters the construction of disease risk maps. We used a Maximum Entropy (MaxEnt) model that associated soil, bioclimatic, and vegetation variables with the best available pathogen presence data collected at anthrax carcass sites to map areas of most likely Bacillus anthracis (the causative bacterium of anthrax) persistence. We then used a hidden Markov model (HMM) to distinguish foraging and non-foraging behavioral states along the movement tracks of nine zebra ( Equus quagga ) during the 2009 and 2010 anthrax seasons. The resulting tracks, decomposed on the basis of the inferred behavioral state, formed the basis of step-selection functions (SSFs) that used the MaxEnt output as a potential predictor variable. Our analyses revealed different risks of exposure during different zebra behavioral states, which were obscured when the full movement tracks were analyzed without consideration of the underlying behavioral states of individuals. Pathogen (or vector) distribution models may be misleading with regard to the actual risk faced by host animal populations when specific behavioral states are not explicitly accounted for in selection analyses. To more accurately evaluate exposure risk, especially in the case of environmentally transmitted pathogens, selection functions could be built for each identified behavioral state and then used to assess the comparative exposure risk across relevant states. The scale of data collection and analysis, however, introduces complexities and limitations for consideration when interpreting results.
... Laganas Bay and around Zakynthos Island, as well as on the neighbouring islands and mainland (Dujon et al., 2018), with different locations potentially supporting different food items of different availability and energetic value (Searle et al., 2005;Seidel & Boyce, 2016). Furthermore, two of the dominant individuals ceased being dominant after 2 years (one frequented the reef intermittently in 2017 before being killed by boat strike, and the other was not recorded at all in 2019e2021). ...
Interactions among individuals of the same species inform us about resource value and sociality; however, for species that are difficult to observe directly, these behaviours are potentially missed or misinterpreted via remote monitoring approaches. Here, we investigated how agonistic interactions influenced temporal and spatial variation in the social structuring of loggerhead sea turtles, Caretta caretta, foraging on sponges at a reef (Zakynthos, Greece) over multiple years. We directly observed individuals via snorkel surveys (with photoidentification and videos) supported by aerial drone surveys. Most turtles were immature loggerheads, of which half were detected in more than 1 year. Individual loggerheads occupied distinct (very small) patches on the reef, with low overlap when foraging. Interactions generally occurred when loggerheads were adjacent to, or passing through, patches occupied by other individuals. Interactions between loggerheads represented an extremely small fraction of the activity budget, but potentially consumed two to three times more energy than swimming and foraging. Escalation of aggression, unexpectedly, skipped the passive (evaluation) phase in half of interactions (starting with biting and chasing), with contests being primarily won by more aggressive individuals, independent of body size and duration of presence (i.e. reef occupancy in years). Distinct hierarchical structuring was detected based on win outcomes and spatial area use within each year; however, the number and combination of turtles frequenting the reef varied across years, with individuals only dominating for 2–3 years before departing (or returning intermittently) and being replaced. The unexpected fight dynamics and regularly changing hierarchies indicate that individuals perceived the resource value of sponges differently, which was attributed to differences in their ability to assess resource abundance and/or availability of resources at alternative sites. Our results contribute to the emerging field of sociality in reptiles.
... Les technologies innovantes nouvellement disponibles couplées à de puissantes méthodologies analytiques (e.g. Brennan et al., 2020;Panzacchi et al., 2016;Seidel and Boyce, 2016) offrent l'opportunité de tester des hypothèses, à condition d'être en mesure de soulever la principale limite de la recherche individuelle en écologie du mouvement, à savoir, le faible nombre d'animaux suivis (Hebblewhite & Haydon, 2010). Comprendre le lien entre une série de gradients de paysages et des caractéristiques comportementales, notamment à travers le mouvement (Van Moorter et al., 2016) peut ainsi permettre de combler certains manques de connaissances, à l'aide de l'écologie du mouvement. ...
Les effets des changements globaux sur les habitats naturels sont de plus en plus perceptibles, et comprendre comment les animaux y répondent est nécessaire pour une meilleure gestion de leurs populations. C’est en effet à travers leur impact sur l’environnement, et essentiellement sur les habitats, que les activités humaines ont souvent le plus grand effet sur les écosystèmes, à travers le changement climatique, la fragmentation, la destruction de l'habitat, les changements dans l'utilisation des terres ou la surexploitation des ressources. Les ongulés constituent un exemple marquant de progression numérique et spatiale d’une guilde d’espèces dans des écosystèmes impactés par l’Homme. Cet essor démographique est à l’origine d’un nombre croissant d’interactions entre Homme et faune et place la gestion de ces espèces au cœur des préoccupations des politiques publiques. Dans ce contexte, j’ai étudié cinq espèces de grands ongulés sauvages : le chamois, le mouflon, le bouquetin, le chevreuil et le cerf, dans le cadre du projet Mov-It (Ungulates MOVing across heterogeneous landscapes: identifying behavioural processes linking global change to spatially-explicIT demographic performance and management), soutenu par l’Agence Nationale de la Recherche (ANR). Dans un premier temps, je mets en évidence les liens entre variations intraspécifiques de la taille du domaine vital saisonnier des ongulés, le paysage (i.e. les ressources, le risque et l’hétérogénéité) et les traits d’histoire de vie de ces espèces. Je me suis ensuite intéressée plus particulièrement à l’influence des structures linéaires anthropiques et naturelles du paysage sur l'utilisation individuelle de l'espace. Je montre ainsi que les grands herbivores utilisent des structures linéaires du paysage pour délimiter leur domaine vital mensuel, mais que l'importance relative de ces structures linéaires dans la délimitation du domaine vital mensuel diminuait à mesure que leur densité augmentait dans le paysage local. Je mets également en évidence le caractère risqué des structures anthropiques pour les ongulés, en particulier l'effet de l'intensité de l’utilisation humaine de ces structures sur le nombre de traversées par les mouflons. Enfin, l’importance de la prise en compte du paysage du risque et des ressources sur l’organisation sociale est démontré. En effet, la formation de dyades (i.e. paires d’individus) est plus probable dans les milieux ouverts riche en ressources et lorsque le risque, incluant prédation et dérangement, est le plus fort (i.e. le jour). L’ensemble des résultats présentés dans ce travail de thèse a permis d’améliorer notre compréhension des effets de la structure du paysage et de la socialité sur la sélection d’habitat et le mouvement chez différentes espèces d’ongulés.
... In addition, some researchers speculated that smaller home ranges may lower the risk of running into predators(Wilson et al. 2018).Herbivores' home ranges varied seasonally, which indicates an adaptation to various environmental factors, for instance, the snow depth, foraging opportunities, and environmental temperatures(Morellet et al. 2013). In winter time, poorer habitat quality, for instance heavy winter snowfalls, lack of foraging opportunities and etc., may force the animal to travel farther away from their homes to seek adequate forage and suitable covers(Seidel and Boyce 2016). In contrast, during the calving seasons, the need for caring young may reduce travelling (Vore and Schmidt 2001; Cho et al. 2016; Yan et al. 2017) ...
Home range size estimation is a crucial basis for developing effective conservation strategies and provides important insights into animal behavior and ecology. This study aimed at analyzing the home range variations, the influence of altitude in habitat selection, and comparing three methods in home range estimation of Chinese gorals ( Naemorhedus griseus ) living at a cliff landscape. The results indicated that there were significant differences between the annual home range sizes of individual animals but there was no difference in their seasonal home range sizes based on GPS tracking data of five female Chinese gorals from February 2015 to September 2018. The monthly home ranges decreased dramatically in May, June and July due to birth-giving. Notable seasonal variations were found in the micro-habitats of the Chinese gorals, as reflected by the altitude they inhabit, with higher altitude habitats used in spring and lower altitude habitats used in winter. Additionally, the altitude of monthly habitats was lowest in January, which may indicate an adaptation to low air temperature. We also found differences between estimation methods, namely minimum convex polygon (MCP), kernel density estimation (KDE) and α-local convex hull (α-LoCoH), with seasonal home range sizes derived from α-LoCoH being substantially smaller than those derived from MCP and KDE. In conclusion, our findings filled the gaps in home range study for this endangered species and contributed to effective conservation strategies. Considerations shall have to be given to the variations in home range estimation caused by different methods when dealing with rugged habitats, so as to make sure that any interpretation concerning the habitat use of the targeted species made on basis of such results would be meaningful and valid.
... Yet, at finer scales in Yellowstone, we have seen trophic-level interactions amplifying spatial heterogeneity through a trophic cascade. Movement among foraging patches might constitute a "shell game" by bison (Harvey and Fortin 2013) and elk (Boyce et al. 2003;Seidel and Boyce 2016) to avoid wolves, another mechanism amplifying spatial and temporal variation in herbivory. The Huffaker effect applies to wolf-ungulate systems at large scales, where some subpopulations might wink in and out (e.g., Isle Royale and Michipicoten Island in Lake Superior), whereas at finer scales, trophic cascades amplify spatial variation in predation risk and consequent herbivory. ...
The reintroduction of gray wolves (Canis lupus) to Yellowstone National Park is the most celebrated ecological experiment in history. As predicted by population models, the rapid recovery of a wolf population caused both temporal and spatial variability in wolf-ungulate interactions that likewise generated temporal and spatial variation in the expression of trophic cascades. This has amplified spatial variation in vegetation in Yellowstone, particularly with willow (Salix spp.) and cottonwood (Populus spp.) in riparian areas, with associated changes in food webs. Increasing influences of grizzly bears (Ursus arctos), cougars (Puma concolor), and bison (Bison bison) are making what initially was predominantly an elk-wolf interaction into an increasingly complex system. Outside Yellowstone, however, humans have a dominant influence in western North America that overwhelms trophic cascades resulting in what appear to be bottom-up influences on community structure and function. Complex and unexpected ecosystem responses to wolf recovery in Yellowstone reinforce the value of national parks and other protected areas as ecological baseline reserves.
... variables (Johnson, Parker, & Heard, 2001;Robbins & Bell, 2000;Seidel & Boyce, 2016). ...
... The risk of predation also leads to different areas being used for specific activities, such as resting and foraging ( Holt 1977, Lima & Dill 1990, Sinclair et al. 1998, Heithaus et al. 2007). Thus, animals make complex decisions regarding their movement patterns within and across patches, and hence adjust their overall home range, in response to multiple variables ( Robbins & Bell 2000, Johnson et al. 2001, Seidel & Boyce 2016). Marine turtles are primarily capital breeders (i.e. ...
During my PhD I obtained new insights on the migration strategies of marine species by utilising Fastloc-GPS tracking and drones. I demonstrated the value of these two emerging technologies to monitor elusive marine species by investigating and reporting on the small-scale movement patterns of sea turtles and the energy expenditure of humpback whales.
... In other instances, aggregation into patches at a fine scale is defensible to identify foraging patches. In elk (Cervus elaphus), foraging occurs in small patches of vegetation followed by larger movements between foraging patches within the home range [23]. However, seasonal ranges are shaped at much larger scales. ...
Purpose of Review
We review and provide comment on issues of scale in ecological studies in the context of two paradigms used to define landscapes: the patch-mosaic and gradient models. Our intent is to offer guidance for structuring habitat-selection models with examples of how scale, autocorrelation, measurement error, and choice of patch-mosaic or gradient models, analysis methods, and covariates by the researcher can influence inferences regarding landscape–organism interactions.
Recent Findings
Methods that allow the organism or data to define the grain and extent of scale of the study offer promise by reducing subjectivity in choices of scale. Ultimately, we recommend that the ecological phenomenon of interest should shape the selection of models defining landscape–organism interaction; however, the choice of model remains with the researcher and is dependent on the research question and the availability of data. Clearly, both the patch-mosaic and gradient models can provide reasonable frameworks for study, and multiple scales that draw from both paradigms often may be most appropriate.
Summary
Scale has been identified as a crucial feature of landscape ecology, yet scale as a paradigm has offered little direction for ecologists. Likewise, debate contrasting gradient models and patch-mosaic models offers few new insights on how ecologists might decide on an appropriate scale for analysis of organism distribution or habitat selection. Various ecological processes influence organisms at different scales and modeling approaches need to be able to accommodate multiple scales simultaneously, which may vary by landscape structure and movement ecology. The continuum of scales and combinations of both gradient and patch-mosaic landscapes provides the necessary array of structures that can be used to construct combinations of landscape covariates that coincide with the ecology of the organism across scales.
... Food resources are clustered into discrete patches of variable quality (Wiens 1976). To forage efficiently, animals generally select patches that offer maximum energy intake for minimal energy expenditure (Charnov 1976;Sims and Quayle 1998;Wei et al. 2015;Mahenya et al. 2016;Seidel and Boyce 2016). However, individuals are likely to adopt different foraging strategies depending on their internal state and external physical and social environment (Pettorelli et al. 2011). ...
In patchy environments, foragers adopt different strategies to acquire resources depending on their internal state and external physical and social environment: this has important fitness consequences. Linking individual variation in patch use to tangible characteristics is key to understand many higher-level ecological processes. We studied patch use by red foxes (Vulpes vulpes) in the city of Bristol, UK. We placed camera traps in gardens where householders provisioned foxes (patches) to investigate whether 1) foxes discriminated between patches based on food availability, quantified as provisioning frequency (predictability) and the energy value of provisioned food; and 2) individual patch use varied with dominance, gender, and season. Increased frequency of provisioning encouraged more foxes to visit and to stay longer in patches. All foxes visited the most predictable patches first each day, but females were more selective and generally more efficient foragers than males. Females increased foraging effort during cub rearing, whereas males reduced patch use in the dispersal and mating season. Dominants and subordinates shared patches spatiotemporally, possibly facilitated by relatedness and familiarity between group members. However, dominants visited more food patches on their territory, spent more time in predictable patches and fed earlier than subordinates. Subordinates may compensate for competition by visiting patches of lower quality or outside their territory, which is inefficient and risky. Our results demonstrate gender differences in behavioral motivation, show how subordinates forego foraging efficiency to mitigate intra-group competition and reveal how human provisioning influences fox space use in urban areas.
... The difference in the location of overlap could hold important information; if the non-overlap section were to fall on different habitat than the overlap section, it might imply that fidelity is based on social dynamics rather than dependency on certain habitat conditions. If the non-overlap section fell on similar habitat, it might imply fidelity to that specific habitat type, with the size of the UD simply fluctuating as conditions in the study area fluctuate, e.g., climatic variability or habitat suitability sensu (Seidel and Boyce, 2016). For example, the reduction in UDs, on average, from 1996 to 1997, was concurrent with a substantial increase in late-season precipitation, suggesting elk had to cover less distance to find forage. ...
Understanding the degree of spatial fidelity exhibited by individuals within a species increases our ability to manage for desired future outcomes. Elk (Cervus elaphus) is a closely managed species in the Western US, but there is little research evaluating their summer home-range fidelity. Elk summer-fall home-ranges overlap considerably with aspen (Populus tremuloides)-dominated forest types, and elk can impact aspen regeneration because it is a preferred browse species. We evaluated the fidelity of 72 adult female elk to individual summer-fall home ranges in northwestern Colorado, USA, during two consecutive summers (1996 and 1997). To compare elk summer-fall home-range overlap and distribution based on individual kernel-estimated utilization distributions, we calculated the volume-of-intersection statistic and the inter-annual distances between centers-of-mass. We found adult female elk in the White River Study area exhibited strong fidelity to individual home ranges. Volume-of-intersection results indicated that 93% of the elk showed explicit home-range overlap between 1996 and 1997, but that all the elk returned to the same vicinity as the previous year (median = 0.42, SE = 0.02, n = 72). Between-year center-of-mass distances ranged from 183 m to 34,170 m (mean = 3819, SE = 619, n = 72), while within-year maximum distances between location points ranged from 4320 m to 31,680 m (mean = 13,958, SE = 628, n = 72). Hunting increased the distance traveled by individual elk, but did not change the center of their home-range. Understanding female elk home-range fidelity could influence forest management focused on aspen regeneration. Specifically, targeted removal of female elk from their summer-fall home ranges could create a ‘window of opportunity’ in which browsing pressure was reduced, and the likelihood of aspen recruitment increased.
... At the temporal resolution of our GPS data, positive directional persistence often is associated with larger distances moved (e.g., during dispersal or migration), while within range or restricted movements are often described by low directional persistence and small distances travelled (Morales et al. 2004;Haydon et al. 2008). We suspect that positive directional persistence could enable elk to avoid recently depleted foraging areas, which might be especially important during winter when there is no forage renewal (Seidel & Boyce 2016). Future work intent on examining directionality and habitat relationships could test for interactions between landscape covariates and turn angle. ...
Roads are a prevalent, ever‐increasing form of human disturbance on the landscape. In many places in western North America, energy development has brought human and road disturbance into seasonal winter range areas for migratory elk.
We sought to evaluate the predictions from the risk‐disturbance hypothesis when studying elk response to roads during winter. Road proximity and crossing were used to evaluate these behaviours, which offered a rare comparison between two common measures of roads. We used integrated step selection analysis ( iSSA ) to evaluate four alternative hypotheses regarding the influence of roads on space‐use behaviour across 175 elk‐years of elk telemetry data, and we quantified both population‐level and individual‐level variations in responses.
We demonstrated, for the first time, how iSSA can be used to combine movement analysis in a refined approach to habitat selection. Elk responded to roads as they would natural predation risk. Elk selected areas farther from roads at all times of day with avoidance being greatest during twilight. In addition, elk sought cover and moved more when in the vicinity of roads. Road crossings were generally avoided, but this avoidance was weakest during daytime when elk were both moving and closer to roads.
Synthesis and applications . Energy development is transforming landscapes in western North America with the proliferation of roads, which we show is having substantial and multifaceted negative effects on elk movement and behaviour. These adverse effects can be mitigated by minimizing new road construction and by restricting traffic on roads as well as providing the protection of tree cover on elk winter ranges.
... Movement patterns reflect strategies to acquire and allocate resources (Van Noordwijk and de Jong 1986, Gaillard et al. 2010, Houston and McNamara 2014, and can provide information about aggregation of resources (Wiens 1976, Seidel andBoyce 2016). For instance, central place foraging patterns, or short forays from a central location, suggest food is localized and has small energetic returns (Giraldeau et al. 1994). ...
Simplifying stand structure to reduce fuel density is a high priority for forest managers; however, affects to Pacific marten (Martes caurina) movement and connectivity are unknown. We evaluated whether thinning forests to reduce fuels influenced movements of Pacific marten. We collected movement paths from 22 martens using global positioning system telemetry to evaluate habitat selection and describe movement patterns. We quantified motion variance, speed, and path sinuosity in 3 stand types that differed in structural complexity (i.e., complex [dense], simple [thinned], and open). We hypothesized marten movement would differ between stand types and predicted that 1) martens would select stand types with increased structural complexity (complex > simple > open); 2) movements would increase in complexity (sinuosity, motion variance) and decrease in speed when martens traveled through stands with increased structural complexity; 3) speeds would increase during summer, indicating increased movement during the breeding season; and 4) males would move more rapidly because of their larger home ranges. Martens traveled 0.5–27.2 km/day and an average (SD) of 1.4 (0.4) km/hour. Martens selected home ranges with fewer openings compared to the study area overall. Within home ranges, martens strongly selected complex stands over simple stands and openings. Speed and movement complexity were most consistent over time and movements were more sinuous and slower in complex stand types compared with openings and simple stands. Movement was erratic and more linear in openings than in both complex and simple stands. In simple stands, movement patterns were intermediate between complex stands and openings. Females generally moved more slowly, sinuously, and less variably compared to males. Martens moved more quickly, less sinuously, and more variably during winter compared to summer. However, martens avoided stands with simplified structure, and the altered patterns of movement we observed in those stands suggested that such treatments may negatively affect the ability of martens to forage without increased risk of predation. Fuel treatments that simplify stand structure negatively affected marten movements and habitat connectivity. Given these risks, and because treating fuels is less justified in high elevation forests, the risks can be minimized by applying treatments below the elevations where martens typically occur.
Home range size estimation is a crucial basis for developing effective conservation strategies and provides important insights into animal behavior and ecology. This study aimed at analyzing the home range variations, the influence of altitude in habitat selection, and comparing three methods in home range estimation of Chinese gorals ( Naemorhedus griseus ) living at a cliff landscape. The results indicated that there were significant differences between the annual home range sizes of individual animals but there was no difference in their seasonal home range sizes based on GPS tracking data of five female Chinese gorals from February 2015 to September 2018. The monthly home ranges decreased dramatically in May, June and July due to birth-giving. Notable seasonal variations were found in the micro-habitats of the Chinese gorals, as reflected by the altitude they inhabit, with higher altitude habitats used in spring and lower altitude habitats used in winter. Additionally, the altitude of monthly habitats was lowest in January, which may indicate an adaptation to low air temperature. We also found differences between estimation methods, namely minimum convex polygon (MCP), kernel density estimation (KDE) and α-local convex hull (α-LoCoH), with seasonal home range sizes derived from α-LoCoH being substantially smaller than those derived from MCP and KDE. In conclusion, our findings filled the gaps in home range study for this endangered species and contributed to effective conservation strategies. Considerations shall have to be given to the variations in home range estimation caused by different methods when dealing with rugged habitats, so as to make sure that any interpretation concerning the habitat use of the targeted species made on basis of such results would be meaningful and valid.
Migrations of large ungulates are globally threatened in environments affected by increasing human disturbance, rising large carnivore predation, deteriorating habitat quality, and changing climate. Animals migrating outside of protected areas can be exposed to greater human pressure, and this effect can be stronger when humans are perceived to be a predation risk, such as during hunting seasons. Using four consecutive years of satellite telemetry data (n = 138 migration events), we compared habitat selection, movement, and behavior of a large partially migratory herbivore while migrating through a heterogeneous landscape in spring and fall. We tested the hypothesis that fall hunting exacerbates the response of a large herbivore exposed to human disturbance while migrating through a road network. All elk (Cervus elaphus) selected greater forest cover, reduced movement rates, and avoided roads during fall-day than in any other season or time of day. Avoidance of roads was reduced during spring at night, for example, the time period of no hunting with fewest people on roads. Elk using stopovers in fall displayed different seasonal and diurnal behaviors between sexes in response to the disturbance. Females used steeper terrain during fall-day and males did not use this strategy in fall. Male avoidance of roads was much stronger than females during fall-day and males were less likely to cross a road during fall. Such responses are probably linked to higher hunting pressure on males vs. females. Finally, we found that elk spent more time feeding during spring migration compared to the fall migration and elk vigilance was >3 times higher in the fall hunting season. Our results provide insights into the effect of fear of humans on the ecology of both sexes of a migrating large herbivore when using stopovers. Such changes in behavior and stopover use might affect animal fitness by decreasing foraging, cause displacement from high-quality habitats, or affect the permeability of migration route stopovers.
Context
In southwestern Alberta, human development, including roads, is encroaching on the landscape and into the range of a partially migratory population of elk (Cervus elaphus).
Objectives
To quantify factors influencing among- and within-home-range selection of winter range in this population.
Methods
We studied individual habitat selection and road avoidance at two biologically relevant spatial scales. We outlined availability extents for 107 individual elk-years based on observed fall migration distance, and based on a minimum convex polygon around winter telemetry relocations. To model the response by elk to road disturbance, we fit a habitat-selection model to each elk-year at each of the two availability extents, and examined population-level and individual variation in space-use. We then evaluated the relationship between inferred selection at the two scales and the functional response in selection.
Results
Roads had a ubiquitous influence on elk across scales. Elk, individually and as a population, avoided roads when migrating to their winter range and within this seasonal home range. Individual elk that avoided roads more strongly relative to the population did so at both scales of analysis.Further, the avoidance of low-use roads decreased with increasing road density. These results support bottom-up habitat-selection patterns (i.e., scale-independent) and functional response in habitat selection.
Conclusions
Overall, using a multi-scale habitat selection analysis, we show that road avoidance is a major determinant of elk space-use behaviour across multiple scales. Consequently, any new road construction or increases in road-use intensity could have detrimental effects on migratory elk populations by restricting space-use.
Rocky Mountain elk (Cervus elaphus nelsoni), Rocky Mountain mule deer (Odocoileus hemionus hemionus), and cattle frequently co-occur on landscapes in the northwestern United States. We hypothesized that niche overlap would be greatest between introduced cattle with either of the 2 native herbivores because coevolution between native elk and mule deer should have resulted in strong patterns of resource partitioning. We observed strong differences among species in use of space, especially elevation, steepness of slope, and use of logged forests. We used 2 temporal windows to examine both immediate (6 h) and long-term (7 days) effects of competition. We noted strong avoidance over a 6-h period among the 3 ungulates. That effect was weaker for the previous 7 days. Cattle were generalists with respect to habitat selection; the 2 native herbivores avoided areas used by cattle. Mule deer and elk avoided one another during the short temporal window (6 h), although spatial differences in habitat use often were not maintained over 7 days. Elk used lower elevations when cattle were absent and moved to higher elevations when cattle were present, indicating shifts in niche breadth and competitive displacement of elk by cattle. We demonstrated strong partitioning of resources among these 3 species, and presented evidence that competition likely has resulted in spatial displacement.
An understanding of sexual segregation is important in the explanation of life history and social preference, population dynamics and the conservation of rare species. This book explores the reasons why this behaviour has evolved and what factors contribute to it. Males and females of many species can, and do, live separately for long periods of time. This sexual segregation is widespread and can be on social, spatial or habitat scales. © Cambridge University Press 2005 and Cambridge University Press, 2009.
An adaption of the optimal foraging theory suggests that herbivores deplete, depart, and finally return to foraging patches leaving time for regrowth [van Moorter et al., Oikos 118:641–652, 2009]. Inter-patch movement and memory of patches then produce a periodic pattern of use that may define the bounds of a home range. The objective of this work was to evaluate the underlying movements within home ranges of elk (Cervus elaphus) according to the predictions of this theory. Using a spatial temporal permutation scan statistic to identify foraging patches from GPS relocations of cow elk, we evaluated return patterns to foraging patches during the 2012 growing season. Subsequently, we used negative binomial regression to assess environmental characteristics that affect the frequency of returns, and thereby characterize the most successful patches.
We found that elk return to known patches regularly over a season, on average after 15.4 (±5.4 SD) days. Patches in less-rugged terrain, farther from roads and with high productivity were returned to most often when controlling for the time each patch was known to each elk.
Instead of diffusion processes often used to describe animal movement, our research demonstrates that elk make directed return movements to valuable foraging sites and, as support for Van Moorter et al.’s [Oikos 118:641–652, 2009] model, we submit that these movements could be an integral part of home-range development in wild ungulates.
Guidelines for use of wild mammal species are updated from the American Society of Mammalogists (ASM) 2007 publication. These revised guidelines cover current professional techniques and regulations involving mammals used in research and teaching. They incorporate additional resources, summaries of procedures, and reporting requirements not contained in earlier publications. Included are details on marking, housing, trapping, and collecting mammals. It is recommended that institutional animal care and use committees (IACUCs), regulatory agencies, and investigators use these guidelines as a resource for protocols involving wild mammals. These guidelines were prepared and approved by the ASM, working with experienced professional veterinarians and IACUCs, whose collective expertise provides a broad and comprehensive understanding of the biology of nondomesticated mammals in their natural environments. The most current version of these guidelines and any subsequent modifications are available at the ASM Animal Care and Use Committee page of the ASM Web site (http://mammalsociety.org/committees/index.asp).
We tested performance of 3 aspects of an elk (Cervus elaphus)-road density model that has been used extensively throughout western North America but has not been sufficiently validated. First, we tested the hypothesis that elk selection of habitats increases with increasing distance away from open roads. This forms the empirical basis for the model. Second, we compared the model's predictions of relative elk habitat selection, or habitat effectiveness (HE), with observed values at varying levels of road density. And third, we examined the potentially confounding effects of different spatial patterns of roads on model predictions. We conducted our study during spring and summer, 1993-95, at the Starkey Experimental Forest and Range (Starkey), northeast Oregon. Selection ratios were calculated using >100,000 recorded locations of 89 radiocollared female elk, with locations mapped in relation to 0.1-km-wide distance bands away from open roads. Selection ratios increased with increasing distance from open roads, and varied between seasons, but not among years or individual animals. Linear regression models, using distance to open roads as a predictor, accounted for significant variation in selection ratios during spring and summer. Model predictions of HE, as measured by number of elk locations, corresponded only weakly, however, with observed values of HE. The contradictory results of these 2 analyses may be explained in part by our simulation results, which showed that potential reductions in elk HE vary strongly with the spatial pattern of roads, which is not measured by the elk-road density model. Our results suggest that (1) management of roads and related human activities during spring and summer should remain an important consideration for modeling and managing the elk resource; and (2) a spatially explicit road component is needed for elk habitat models.
National parks are important for conservation of species such as wolves (Canis lupus) and elk (Cervus canadensis). However, topography, vegetation conditions, and anthropogenic infrastructure within parks may limit available habitat. Human activity on trails and roads may lead to indirect habitat loss, further limiting available habitat. Predators and prey may respond differentially to human activity, potentially disrupting ecological processes. However, research on such impacts to wildlife is incomplete, especially at fine spatial and temporal scales. Our research investigated the relationship between wolf and elk distribution and human activity using fine-scale Global Positioning System (GPS) wildlife telemetry locations and hourly human activity measures on trails and roads in Banff, Kootenay, and Yoho National Parks, Canada. We observed a complex interaction between the distance animals were located from trails and human activity level resulting in species adopting both mutual avoidance and differential response behaviors. In areas < 50 m from trails human activity led to a mutual avoidance response by both wolves and elk. In areas 50 -400 m from trails low levels of human activity led to differential responses; wolves avoided these areas, whereas elk appeared to use these areas as a predation refugia. These differential impacts on elk and wolves may have important implications for trophic dynamics. As human activity increased above two people/hour, areas 50 -400 m from trails were mutually avoided by both species, resulting in the indirect loss of important montane habitat. If park managers are concerned with human impacts on wolves and elk, or on these species' trophic interactions with other species, they can monitor locations near trails and roads and consider hourly changes of human activity levels in areas important to wildlife.
Background
In disease surveillance, the prospective space-time permutation scan statistic is commonly used for the early detection of disease outbreaks. The scanning window that defines potential clusters of diseases is cylindrical in shape, which does not allow incorporating into the cluster shape potential factors that can contribute to the spread of the disease, such as information about roads, landscape, among others. Furthermore, the cylinder scanning window assumes that the spatial extent of the cluster does not change in time. Alternatively, a dynamic space-time cluster may indicate the potential spread of the disease through time. For instance, the cluster may decrease over time indicating that the spread of the disease is vanishing.
Methods
This paper proposes two irregularly shaped space-time permutation scan statistics. The cluster geometry is dynamically created using a graph structure. The graph can be created to include nearest-neighbor structures, geographical adjacency information or any relevant prior information regarding the contagious behavior of the event under surveillance.
Results
The new methods are illustrated using influenza cases in three New England states, and compared with the cylindrical version. A simulation study is provided to investigate some properties of the proposed arbitrary cluster detection techniques.
Conclusion
We have successfully developed two new space-time permutation scan statistics methods with irregular shapes and improved computational performance. The results demonstrate the potential of these methods to quickly detect disease outbreaks with irregular geometries. Future work aims at performing intensive simulation studies to evaluate the proposed methods using different scenarios, number of cases, and graph structures.
We applied optimal foraging theory to test effects of habitat and predation risk on foraging behavior of mule deer (Odocoileus hemionus) subject to predation by mountain lions (Puma concolor). We predicted that deer would spend less time foraging, have higher giving-up densities of food (GUDs), and have higher vigilance behavior when occupying patch edges than when in open and forest interiors. We also measured GUDs in 3 microhabitats within 3 forest types. We used pellet-group surveys to estimate habitat and microhabitat use, and we assessed vigilance behavior with automatic camera systems. The GUDs (perceived predation risk) were greater in forests of Douglas fir (Pseudostuga menziensii) than moun-tain mahogany (Cercocarpus ledifolius). In forests of Douglas fir, GUDs were greatest in the forest interior, declined at the forest edge, and were lowest in the open microhabitat. Microhabitat features did not influence GUDs in the mountain mahogany forest. Pellet-group data indicated more activity in the open than in the edge or forest. Based on pho-tographs, deer were more vigilant at forest edges than in open and forest areas. We con-cluded that deer are responding to predation risk by biasing their feeding efforts at the scale of habitats and microhabitats and altering their habitat-specific patterns of vigilance behavior.
1. Summer home range size variation and habitat selection of 35 radio-collared adult female roe deer was studied, using kernel home range estimation and compositional analysis of habitat use. 2. Female roe deer adjust the size of their home range in response to decreasing food supply, and the hypothesis that female roe deer utilize the minimum area that sustain their energy requirement cannot be rejected. 3. Home range size increased with the visibility in the home range (the average distance at which sight is blocked by intervening vegetation). This supports the hypothesis that cover is important in reducing the risk of predation and thereby increasing adult survival. 4. Female roe deer spend more time near habitat edges, supporting the hypothesis that different habitat types contain complementary resources, e.g. food and cover or different nutrients. Simultaneous access to several habitat types did not have any effect on home range size, possibly because variation in heterogeneity between different home ranges was too low. 5. Females without fawns had smaller home ranges, possibly because they only need to sustain their own energetic requirements. 6. The analyses of habitat selection inside each home range showed that the forest types, characterized by high densities of food and low visibility, were preferred, suggesting that habitat use is allocated in proportion to either food or cover or both.
Human disturbance can influence wildlife behaviour, which can have implications for wildlife populations. For example, wildlife may be more vigilant near human disturbance, resulting in decreased forage intake and reduced reproductive success. We measured the effects of human activities compared to predator and other environmental factors on the behaviour of elk (Cervus elaphus Linnaeus 1758) in a human-dominated landscape in Alberta, Canada.
We collected year-round behavioural data of elk across a range of human disturbances. We estimated linear mixed models of elk behaviour and found that human factors (land-use type, traffic and distance from roads) and elk herd size accounted for more than 80% of variability in elk vigilance. Elk decreased their feeding time when closer to roads, and road traffic volumes of at least 1 vehicle every 2 hours induced elk to switch into a more vigilant behavioural mode with a subsequent loss in feeding time. Other environmental factors, thought crucial in shaping vigilance behaviour in elk (natural predators, reproductive status of females), were not important. The highest levels of vigilance were recorded on public lands where hunting and motorized recreational activities were cumulative compared to the national park during summer, which had the lowest levels of vigilance.
In a human-dominated landscape, effects of human disturbance on elk behaviour exceed those of habitat and natural predators. Humans trigger increased vigilance and decreased foraging in elk. However, it is not just the number of people but also the type of human activity that influences elk behaviour (e.g. hiking vs. hunting). Quantifying the actual fitness costs of human disturbance remains a challenge in field studies but should be a primary focus for future researches. Some species are much more likely to be disturbed by humans than by non-human predators: for these species, quantifying human disturbance may be the highest priority for conservation.
Rocky Mountain elk (Cervus elaphus nelsoni), Rocky Mountain mule deer (Odocoileus hemionus hemionus), and cattle frequently co-occur on landscapes in the northwestern United States. We hypothesized that niche overlap would be greatest between introduced cattle with either of the 2 native herbivores because coevolution between native elk and mule deer should have resulted in strong patterns of resource partitioning. We observed strong differences among species in use of space, especially elevation, steepness of slope, and use of logged forests. We used 2 temporal windows to examine both immediate (6 h) and long-term (7 days) effects of competition. We noted strong avoidance over a 6-h period among the 3 ungulates. That effect was weaker for the previous 7 days. Cattle were generalists with respect to habitat selection; the 2 native herbivores avoided areas used by cattle. Mule deer and elk avoided one another during the short temporal window (6 h), although spatial differences in habitat use often were not maintained over 7 days. Elk used lower elevations when cattle were absent and moved to higher elevations when cattle were present, indicating shifts in niche breadth and competitive displacement of elk by cattle. We demonstrated strong partitioning of resources among these 3 species, and presented evidence that competition likely has resulted in spatial displacement.
Road closures frequently are used to manage for Rocky Mountain elk (Cervus elaphus nelsoni), but no studies have evaluated the effects of limited vehicle access on movements and survival of Roosevelt elk (C. elaphus roosevelti). We studied movements and survival of female Roosevelt elk before Road Management Areas (RMA) were designated, and during limited vehicular access from 1991 to 1995. The Bureau of Land Management (BLM) instituted a limited-vehicle access program on 35% of the study area in 1992. We found a reduction in core area size (P = 0.002) and home range size (P = 0.077) during limited vehicle access. There was also a reduction in daily movement of elk (P = 0.0001), and there was a negative correlation between daily movements and percent association of elk home ranges with RMA. There was an increase in survival rate (P = 0.03) during the limited-vehicular access period compared to the pre-RMA period, and survival rate declined following the removal of the gates (P = 0.05). Our data suggest that limited-vehicular access reduces human disturbance that results in reduced movements and poaching (increased survival) of Roosevelt elk. Such methods should be considered for other elk populations.
The forage maturation hypothesis (FMH) proposes that ungulate migration is driven by selection for high forage quality. Because quality declines with plant maturation, but intake declines at low biomass, ungulates are predicted to select for intermediate forage biomass to maximize energy intake by following phenological gradients during the growing season. We tested the FMH in the Canadian Rocky Mountains by comparing forage availability and selection by both migrant and nonmigratory resident elk (Cervus elaphus) during three growing seasons from 2002–2004. First, we confirmed that the expected trade-off between forage quality and quantity occurred across vegetation communities. Next, we modeled forage biomass and phenology during the growing season by combining ground and remote-sensing approaches. The growing season started 2.2 days earlier every 1 km east of the continental divide, was delayed by 50 days for every 1000-m increase in elevation, and occurred 8 days earlier on south aspects. Migrant and resident selection for forage biomass was then compared across three spatial scales (across the study area, within summer home ranges, and along movement paths) using VHF and GPS telemetry locations from 119 female elk. Migrant home ranges occurred closer to the continental divide in areas of higher topographical diversity, resulting in migrants consistently selecting for intermediate biomass at the two largest scales, but not at the finest scale along movement paths. In contrast, residents selected maximum forage biomass across all spatial scales. To evaluate the consequences of selection, we compared exposure at telemetry locations of migrant and resident elk to expected forage biomass and digestibility. The expected digestibility for migrant elk in summer was 6.5% higher than for residents, which was corroborated with higher fecal nitrogen levels for migrants. The observed differences in digestibility should increase migrant elk body mass, pregnancy rates, and adult and calf survival rates. Whether bottom-up effects of improved forage quality are realized will ultimately depend on trade-offs between forage and predation. Nevertheless, this study provides comprehensive evidence that montane ungulate migration leads to greater access to higher-quality forage relative to nonmigratory congeners, as predicted by the forage maturation hypothesis, resulting primarily from large-scale selection patterns.
Models of habitat selection have been developed primarily for mobile animals with well-defined home ranges. The assumptions made by traditional techniques about habitat availability are inappropriate for species with low mobility and large home ranges, such as the wood turtle. We used paired logistic regression, typically used in medical case control studies, to model selection of habitat within activity areas in a population of wood turtles in a watershed in western Maine. We also modeled selection of activity areas within the watershed, using nonpaired logistic regression. Within activity areas, wood turtles selected nonforested locations close to water with low canopy cover. Within the watershed, they selected activity areas close to streams and rivers with moderate forest cover and little open water. The difference between selection at these two scales suggests that wood turtles select forest edges to balance thermoregulatory and feeding needs. The model of selection of activity areas within the watershed correctly classified 84% of activity areas and random areas. This model may be useful for identifying wood turtle habitat across the landscape as part of regional conservation efforts. We suggest that paired logistic regression shows promise for analysis of habitat selection of species with movement patterns that violate the assumptions of traditional habitat selection models.
Although herbivores are generally known to trade off forage in open habitat patches and cover in forested habitat patches, it remains unclear if high population density and low predation risk can modulate the trade-off between forage and cover. We studied a population of white-tailed deer (Odocoileus virginianus) that was at high density and on a large island free of predators to assess the influence of forage and cover on habitat selection under harsh environmental conditions. We fitted 19 female white-tailed deer with global positioning system collars and delineated summer home ranges and core areas. We sampled vegetation in the core areas and in the rest of the home ranges to determine abundance of forage and forest cover within habitat patches, and assessed habitat selection between open and forested habitat patches. At a coarse scale, white-tailed deer preferred open habitat patches over forested ones, suggesting that they adopted a foraging strategy favoring energy intake. At a fine scale, habitat selection was influenced positively by the percentage of ground cover of forbs and deciduous shrubs, but negatively by conifer density. The biomass of preferred plant species, lateral cover, fir regeneration, and distance to the nearest open–forest edge were not strong predictors of habitat selection by deer. We conclude that fine-scale habitat selection by white-tailed deer at high population density and in the absence of predation is mainly determined by forage abundance. These patterns of habitat selection demonstrate that herbivores can adjust their behavior to other limiting factors when predation risk is relaxed.
Many classical models of ungulate foraging are premised on energy maximization, yet limited empirical evidence and untested currency assumptions make the choice of currency a non‐trivial issue. The primary constraints on forage intake of ungulates are forage quality and availability. Using a model that incorporates these two constraints, we predicted the optimal biomass of forage patches for ungulate grazers using an energy maximizing vs. a time minimizing strategy.
We tested these predictions on wood bison ( Bison bison athabascae Rhoads) grazing naturally occurring sedge ( Carex atherodes Spreng). The digestive constraint was determined by a series of ad libitum feeding trials using sedge at different stages of growth. Sedge digestibility declined with biomass. Ad libitum intake of sedge by bison declined with sedge digestibility and thus decreased with sedge biomass. On the other hand, short‐term sedge intake rates of wood bison increased with biomass.
Incorporation of these constraints resulted in the prediction that daily energy gain of bison should be maximized by grazing patches with a biomass of 10 g m ⁻² , whereas a bison could minimize daily foraging time needed to fulfil its energy requirement by cropping patches with a biomass of 279 g m ⁻² .
To test these quantitative predictions, we used a staggered mowing regime to convert even‐aged stands of sedge to a mosaic of patches varying in quality and quantity. Observations of bison grazing these mosaics indicated that patches of biomass below 120 g m ⁻² were avoided, while patches of biomass 156 and 219 g m ⁻² were highly preferred, with the greatest preference for the latter.
These results indicate that bison were behaving as time minimizers rather than energy maximizers. Daily cropping times of free‐ranging bison from the literature corroborate our results.
Despite its central place in animal ecology no general mechanistic movement model with an emergent home-range pattern has yet been proposed. Random walk models, which are commonly used to model animal movement, show diffusion instead of a bounded home range and therefore require special modifications. Current approaches for mechanistic modeling of home ranges apply only to a limited set of taxa, namely territorial animals and/or central place foragers. In this paper we present a more general mechanistic movement model based on a biased correlated random walk, which shows the potential for home-range behavior. The model is based on an animal tracking a dynamic resource landscape, using a biologically plausible two-part memory system, i.e. a reference- and a working-memory. Our results show that by adding these memory processes the random walker produces home-range behavior as it gains experience, which also leads to more efficient resource use. Interestingly, home-range patterns, which we assessed based on home-range overlap and increase in area covered with time, require the combined action of both memory components to emerge. Our model has the potential to predict home-range size and can be used for comparative analysis of the mechanisms shaping home-range patterns.
Animals may respond to spatial and temporal heterogeneity by altering their movement patterns. The time an animal spends in an area of a given size is termed ȁ8first-passage timeȁ9 and can be used to identify the scales at which different movement processes occur. Using first-passage time and 2-h observations, we identified nested spatial scales representing three movement behaviours for elk (Cervus elaphus) – inactive/resting (moves Canis lupus), farther than 50m from anthropogenic linear clearings, and where microclimatic conditions were cool (high shrub cover and north to east-facing slopes). In contrast, elk were most likely to forage in areas having intermediate levels of herbaceous biomass and low movement costs. Elk were most likely to be relocating when in areas of high wolf use, when close to linear clearings, and in energetically costly situations such as moving upslope. We discuss how elk use of potential foraging habitats may be restricted in this landscape by risks imposed by predators, humans, or both.
Although there is ample evidence for the generality of foraging and predation trade-offs in aquatic systems, its application
to terrestrial systems is less comprehensive. In this review, meta-analysis was used to analyze experiments on giving-up-densities
in terrestrial systems to evaluate the overall magnitude of predation risk on foraging behavior and experimental conditions
mediating its effect. Results indicate a large and significant decrease in foraging effort as a consequence of increased predation
risk. Whether experiments were conducted under natural or artificial conditions produced no change in the overall effect predation
had on foraging. Odor and live predators as a correlate of predation risk had weaker and nonsignificant effects compared to
habitat characteristics. The meta-analysis suggests that the effect of predation risk on foraging behavior in terrestrial
systems is strongly dependent on the type of predation risk being utilized.
Home ranges of animals are associated with the spatial distribution of limiting resources on a landscape, yet no mechanistic models representing this relationship exist. We present models of how animals might choose patches for their home ranges in ways that are optimal with respect to spatially distributed resources. The models assume that animals choose patches for their home ranges based on resource benefits discounted for travel costs. Animals might select patches to maximize resources within their home ranges over random use of the landscape (resource maximization), or to satisfy a minimum resource threshold needed for survival or reproduction (area minimization). We evaluated how landscape configuration structures home ranges of animals by performing individual-based, spatially explicit computer simulations using each model on simulated landscapes that differed only in the spatial continuity of resources among patches (from over-dispersed to clumped). The most important factor determining quality, efficiency, resource content, and spatial distribution of home ranges was the extent to which resources were clumped on a landscape. Characteristics of resource-maximizing home ranges were determined only by the distribution of resources, and differed from those of area-minimizing home ranges depending upon the magnitude of the resource threshold required. An increase in resource threshold increased area and total resource content for area-minimizing home ranges, but did not change their quality or efficiency. Because animals can consume or protect resources within their home ranges, they can depress the value of resources available to other animals and hence how those animals will choose their home ranges. Depression of resource values on a landscape by animals should result in different configuration and spatial distribution of home ranges on a landscape than would be predicted in its absence. We modified the two home range models to depress the value of resources available to other animals within patches selected for each home range. We generated home ranges with the new models on the simulated landscapes and evaluated how home ranges with resource depression varied with landscape configuration and with the number of home ranges on the landscape. We compared characteristics and spatial distribution of home ranges with resource depression to those of home ranges that do not. For the number of simulations we performed, resource depression resulted in home ranges that differed little in configuration and landscape interactions from those without, except that they were distributed more evenly on the landscapes and overlapped each other less. As the number of home ranges on a landscape increased, resource distributions declined in quality and heterogeneity, and home ranges became larger, less efficient, and of lower quality. Our results suggest that, in addition to landscape configuration, the extent to which animals depress resources included in their home ranges should determine the evenness of spatial dispersion, overlap, and home range structure, especially where animals select home ranges to satisfy a specific resource threshold and the density of animals is high. Because resource depression sets a limit on the number of home ranges a landscape with fixed resource levels can support, our models provide a means of assessing carrying capacity of a landscape.
Spatial patterns of movement are fundamental to the ecology of animal populations, influencing their social organization, mating systems, demography, and the spatial distribution of prey and competitors. However, our ability to understand the causes and consequences of animal home range patterns has been limited by the descriptive nature of the statistical models used to analyze them. In Mechanistic Home Range Analysis, Paul Moorcroft and Mark Lewis develop a radically new framework for studying animal home range patterns based on the analysis of correlated random work models for individual movement behavior. They use this framework to develop a series of mechanistic home range models for carnivore populations. The authors' analysis illustrates how, in contrast to traditional statistical home range models that merely describe pattern, mechanistic home range models can be used to discover the underlying ecological determinants of home range patterns observed in populations, make accurate predictions about how spatial distributions of home ranges will change following environmental or demographic disturbance, and analyze the functional significance of the movement strategies of individuals that give rise to observed patterns of space use. By providing researchers and graduate students of ecology and wildlife biology with a more illuminating way to analyze animal movement, Mechanistic Home Range Analysis will be an indispensable reference for years to come.
INTRODUCTION Adult males and females of many animal species differ in terms of the taxonomic range of food types they use, and/or the physical and chemical properties of the meals they ingest. Surprisingly, however, recognition and understanding of these differences has advanced slowly. For example, practitioners of wildlife production and conservation typically use total animal numbers for setting stocking rates, estimating area requirements, monitoring plant–animal interactions, etc., with no consideration of sex differences in feeding ecology. Yet the reason why textbooks on wildlife ecology and management (e.g. Caughley & Sinclair, 1994) seldom address sex differences is more the lack of conclusive published information than simple oversight. Hence, my purpose in writing this chapter will be served if it stimulates further research on this ecologically important topic. My focus here is on sex differences in the foraging ecology of large mammalian herbivores (>5 kg), mostly because the principles underlying diet selection have been better studied in this group than in any other. It is obvious that substantial dietary differences will occur when male and female herbivores feed in separate plant communities, the possible reasons for which are discussed in Chapter 9. Here, however, I discuss sex differences in the consumption of plant material by large herbivores at the scale of the small patch, or feeding station (as defined by Senft et al. , 1987). © Cambridge University Press 2005 and Cambridge University Press, 2009.
We studied survival and vulnerability to hunting mortality among adult male, subadult male, and adult female elk (Cervus elaphus; n = 78) in the Cascade Range of south-central Washington, USA, 1992-1999. Among several candidate survival models, the weight of evidence suggested that the data best supported a model wherein survival varied by sex, ( = 0.65 [95% CI: 0.54 to 0.75], = 0.83 [95% CI: 0.70 to 0.91]). Thirty-nine (50%) of the radiomarked elk died during the study. All deaths among subadult (≤4 yr) males and all but 1 death among females were caused by hunting. Eleven of 17 (64.7%) deaths among adult (≥5 yr) males were hunting-related, whereas 5 deaths (29.4%) were independent of hunting. We evaluated 12 candidate logistic regression models relating elk harvest risks to landscape features within summer-autumn home ranges, where most hunting mortalities occurred, using an information-theoretic approach. Akaike model weights indicated that 5 models represented a best-model subset using data from all radiomarked elk and 4 models represented a logical best-model subset when the analysis was limited to data from male elk, although collective Akaike weights differed between the 2 subsets. Several models in the best-model subsets contained road density (km/km2) as an explanatory variable, but models using road density as the only explanatory variable were not among the best-model subsets. Two additional variables appeared to be useful for modeling harvest risks. Aspect diversity, an index of topographic complexity (which influenced hunter effort), and percent of elk home ranges in managed forest were common to several models in the best-model subsets. The managed forest variable indexed the proportion of an elk's home range that was roaded. All models in the best-model subsets had either a road density or percent managed forest variable, suggesting that broadly defined road effects were important sources of harvest vulnerability. For all elk, the model with the highest Akaike weight (56%) used road density and 2 topographic variables to explain elk harvest risks. For male-only data, the best-supported model (weight = 25%) used percent managed forest and aspect diversity as explanatory variables. Our analysis supported the inference that harvest vulnerability in elk in the south-central Cascades was strongly affected by the presence and/or density of open roads, but that topographic complexity influenced the likelihood that elk were killed apart from roading effects.
1. Hypothesis Testing in Ecology, by Charles J. Krebs2: A Critical Review of the Effects of Marking on the Biology of Vertebrates, by Dennis L. Murray and Mark R. Fuller3. Animal Home Ranges and Territories and Home Range Estimators, by Roger A. Powell4. Delusions in Habitat Evaluation: Measuring Use, Selection, and Importance, by David L. Garshelis5. Investigating Food Habits of Terrestrial Vertebrates, by John A. Litvaitis6. Detecting Stability and Causes of Change in Population Density, by Joseph S. Elkinton7. Monitoring Populations, by James P. Gibbs8. Modeling Predator--Prey Dynamics, by Mark S. Boyce9. Population Viability Analysis: Data Requirements and Essential Analyses, by Gary C. White10. Measuring the Dynamics of Mammalian Societies: An Ecologist's Guide to Ethological Methods, by David W. Macdonald, Paul D. Stewart, Pavel Stopka, and Nobuyuki Yamaguchi11. Modeling Species Distribution with GIS, by Fabio Corsi, Jan de Leeuw, and Andrew K. Skidmore
Cover is one of the more commonly measured quantities in vegetation sampling. Measurement of basal area may be more reliable for estimation of cover changes for some species than foliage cover because basal cover fluctuates less during seasonal periods of precipitation or other perturbations. Line intercept and point intercept methods are two of the most popular methods used to estimate cover, and are variable plot sampling units. There are two other important variable area techniques used extensively for cover determination: (1) Bitterlich's “variable-radius method” for tree basal area and shrub canopy area, and (2) the “point-centered quarter method” (PCQ) to determine cover simultaneously with stem density. Many plant ecologists are interested in qualitative attributes of species rather than quantitative attributes. Some qualitative methods can be used for mathematical computations of data and, thus, are suitable for statistical analysis. These methods can appropriately be referred to as semi-quantitative.
WE propose here a mechanism for territorial pattern formation in wolves (Canis lupus) and analyse it using a spatially explicit mathematical model incorporating wolf movement and scent marking. Model results reflect field observations from northeastern Minnesota: buffer zones where wolves are scarce arise between adjacent packs, and near these buffer zones there are increased levels of scent marking1,2. Territories are arranged in a spatial mosaic (Fig. 1) which covers the wolf range. In the model formulation no assumptions are made about actual existence or extent of wolf territory and buffer zones; these arise naturally as stable steady-state solutions to the equations. We show mathematically how reduced predation by wolves in the buffer zones provides a refuge for prey species. Field studies support this; distribution of a primary prey species, white-tailed deer (Odocoileus virginianus), correlates negatively with that of wolves. Deer are found primarily in buffer zones3,4 (Fig. 2).
The traditional models used to characterize animal home ranges have no
mechanistic basis underlying their descriptions of space use, and as a
result, the analysis of animal home ranges has primarily been a
descriptive endeavor. In this paper, we characterize coyote (Canis
latrans) home range patterns using partial differential equations for
expected space use that are formally derived from underlying
descriptions of individual movement behavior. To our knowledge, this is
the first time that mechanistic models have been used to characterize
animal home ranges. The results provide empirical support for a model
formulation of movement response to scent marks, and suggest that having
relocation data for individuals in adjacent groups is necessary to
capture the spatial arrangement of home range boundaries. We then show
how the model fits can be used to obtain predictions for individual
movement and scent marking behavior and to predict changes in home range
patterns. More generally, our findings illustrate how mechanistic models
permit the development of a predictive theory for the relationship
between movement behavior and animal spatial distribution.
Timber management is the most prominent land management activity in the Black Hills National Forest in the northcentral United States. Management units are stands 4–32ha in size and are described using a hierarchal vegetative description including vegetation type, size class (age), and overstory canopy cover. For the most part, these stands are relatively homogeneous resulting from decades of even-aged management. Because elk (Cervus elaphus) select habitats at different scales from home ranges to microsites, it is important for managers to know how elk utilize vegetative conditions within these stands. We compared vegetative conditions at microsites selected by elk to the vegetative conditions of similarly classified stands to enable managers to better understand how timber management affects elk habitat. Within these relatively homogeneous forest stands under even-age management of the Black Hills, elk demonstrated selection for particular forest attributes. Vegetative conditions that provide cover for elk were selected for in open stands (both aspen and pine), but while in dense stands, elk selected for more open conditions. The elk hiding cover model should be adjusted for this forest.
Elk (Cervus elaphus) in the Jackson herd in northwestern Wyoming, U.S.A., migrate as far as 100 km from high-elevation summer ranges to winter ranges and feed grounds at lower elevations where there is less snow. Selection favoring migratory tendency in elk has resulted in high fidelity to seasonal ranges and migration routes in the Jackson elk herd. However, migratory behavior is not genetically fixed as some interbreeding herds adjacent to the Jackson herd are resident whilst others are migratory or nomadic. The proximal factor stimulating autumn migration is clearly snowfall, whereas spring migration appears to follow snowmelt and greenup. Migratory behavior creates certain management difficulties because elk cross lands under various management jurisdictions. Fidelity to seasonal ranges also has important implications for harvest policy because local distribution has been substantially altered by hunting. To restore historical distribution of elk in the Jackson herd would require an increase in the controversial culling program within Grand Teton National Park. Careful timing of mining and logging operations on seasonal ranges and migration routes can minimize their disturbance effects on elk distribution.
The line interception method as herein described is designed for measuring density and composition of herbaceous vegetation and shrubs. It is based primarily on the line transect. However, it incorporates a new technique for obtaining an inventory of the vegetation by line measurement of individual plants on a randomly selected sample. It appears to offer a practical, rapid and statistically sound means for sampling vegetation on both large and small range areas, as well as on small plots used in detailed and intensive studies. Field tests have demonstrated that subjective influences are largely eliminated as factors affecting inventories so obtained. The method while primarily developed for range studies should also serve equally well to measure minor vegetation and stands of reproduction in forests.
Inter-sexual segregation between habitats or between sites within a habitat is very widespread in sexually dimorphic ungulates. As an explanation, it has been suggested that males, because of their larger forage requirements, are driven from preferred, high quality forage habitats into marginal habitats of lower forage quality but higher forage biomass by female competition (‘indirect competition hypothesis’). However, this hypothesis has hardly been tested. In the present study, we tested the indirect competition hypothesis for site segregation of red deer on the Isle of Rum, Scotland, within two vegetation communities: short Agrostis/Festuca grassland and Calluna heath. We predicted that: (1) males should choose sites within each vegetation community that are of higher forage biomass but lower forage quality, than sites selected by females; (2) the degree of inter-sexual site segregation should be highest within the vegetation community in which indirect competition was most intense. We found that the sexes were significantly segregated between sites within both vegetation communities, but males did not use sites of lower forage quality or of higher forage biomass than did females. Moreover, degree of site segregation was not significantly higher in the vegetation community in which competition was more intense (i.e. short Agrostis/Festuca grassland). We conclude that the indirect competition hypothesis cannot explain site segregation in red deer on the Isle of Rum.
Roads cause functional habitat loss, alter movement patterns and can become ecological traps for wildlife. Many of the negative effects of roads are likely to be a function of the human use of roads, not the road itself. However, few studies have examined the effect of temporally and spatially varying traffic patterns on large mammals, which could lead to misinterpretations about the impact of roads on wildlife.
We developed models of traffic volume for an entire road network in south-western Alberta, Canada, and documented for the first time the response of grizzly bears Ursus arctos L to a wide range of traffic levels.
Traffic patterns caused a clear behavioural shift in grizzly bears, with increased use of areas near roads and movement across roads during the night when traffic was low. Bears selected areas near roads travelled by fewer than 20 vehicles per day and were more likely to cross these roads. Bears avoided roads receiving moderate traffic (20–100 vehicles per day) and strongly avoided high-use roads (>100 vehicles per day) at all times.
Synthesis and applications. Grizzly bear responses to traffic caused a departure from typical behavioural patterns, with bears in our study being largely nocturnal. In addition, bears selected private agricultural land, which had lower traffic levels, but higher road density, over multi-use public land. These results improve our understanding of bear responses to roads and can be used to refine management practices. Future management plans should employ a multi-pronged approach aimed at limiting both road density and traffic in core habitats. Access management will be critical in such plans and is an important tool for conserving threatened wildlife populations.
Most studies of habitat selection by large herbivores focus on the resource availability and interactions with other species, but neglect the importance of an animal being familiar with an area due to past use. Yet, studies of the establishment and retention of territories, home ranges, birth sites, and feeding site choices in experimental settings have shown the importance of spatial familiarity at these scales. We used GPS locations of translocated wapiti Cervus elaphus, resource selection functions (RSF), and time-to-return to examine whether previous site use was important for selection of sites by wapiti in west-central Alberta. To construct RSFs, we used logistic regression that included spatial familiarity (presence of a previous GPS location within a 50-m radius) as well as estimates of herbaceous and shrub biomass, elevation, aspect, slope, and predation risk to wapiti from wolf predation, as dependent variables. We found that previous use had a strong positive relationship with subsequent site use, indicating that wapiti were not avoiding previously visited locations, as would be expected if memory of forage depletion (which we did not measure) determined response to familiar locations. Revisited sites were of higher quality, i.e. had more moderate terrain, higher forage, and lower predation risk, than sites that were not revisited, indicating that the selection of familiar locations was likely not the result of avoidance of unfamiliar locations. Finally, animals demonstrated preference for familiar locations that it had visited most recently, indicating that memory (which would decline with time) of higher site quality, rather than high quality alone, influenced selection for familiar locations. We conclude that spatial familiarity is important not only for large scale processes such as selection of home range and territory, but for smaller scale habitat selection and foraging as well.
1Nutrition influences most aspects of animal ecology: juvenile growth rates and adult mass gain, body condition, probability of pregnancy, over-winter survival, timing of parturition, and neonatal birth mass and survival. We provide an overview among ungulates of the extent of these influences resulting from interactions among bioenergetics, foraging, and nutritional demands.2 Body condition of an animal is the integrator of nutritional intake and demands, affecting both survival and reproduction. The deposition and mobilization of body fat and body protein vary with physiological requirements and environmental conditions as species use dietary income and body stores to integrate the profits of summer and the demands of winter. Results from our simulation model and uncertainty analysis of the influence of body mass and changes in body composition of Rangifer over winter indicate that percent body fat rather than body mass in early winter is most important in determining whether animals die, live with
Accurate estimates of kill rates remain a key limitation to addressing many predator—prey questions. Past approaches for identifying kill sites of large predators, such as wolves (Canis lupus), have been limited primarily to areas with abundant winter snowfall and have required intensive ground-tracking or aerial monitoring. More recently, attempts have been made to identify clusters of locations obtained using Global Positioning System (GPS) collars on predators to identify kill sites. However, because decision rules used in determining clusters have not been consistent across studies, results are not necessarily comparable. We illustrate a space—time clustering approach to statistically define clusters of wolf GPS locations that might be wolf kill sites, and we then use binary and multinomial logistic regression to model the probability of a cluster being a non—kill site, kill site of small-bodied prey species, or kill site of a large-bodied prey species. We evaluated our approach using field visits of kills and assessed the accuracy of the models using an independent dataset. The cluster-scan approach identified 42–100% of wolf-killed prey, and top logistic regression models correctly classified 100% of kills of large-bodied prey species, but 40% of small-bodied prey species were classified as nonkills. Although knowledge of prey distribution and vulnerability may help refine this approach, identifying small-bodied prey species will likely remain problematic without intensive field efforts. We recommend that our approach be utilized with the understanding that variation in prey body size and handling time by wolves will likely have implications for the success of both the cluster scan and logistic regression components of the technique. (JOURNAL OF WILDLIFE MANAGEMENT 72(3):798–807; 2008)
We studied factors which may shape giving-up decisions of wapiti grazing grassland patches (area where a wapiti initiates and terminates a feeding sequence) and feeding stations (area within a patch that a wapiti can reach without moving its forelegs). In grassland patches, cropping rate decreased after a critical period, whereas at feeding stations cropping rate increased with cumulative bites consumed. The number of feeding stations grazed, number of bites taken and grazing time did not dictate the termination of grazing in a patch. Wapiti gave up a patch only after the cropping rate at a feeding station dropped below the seasonal expectation during trials on lush pasture in May, but gave up after the cropping rate dropped below the seasonal expectation at two consecutive feeding stations in March/April and August when foraging conditions were less favourable. This confirmed a prediction of the marginal value theorem. Wapiti did not give up a feeding station according to bites taken, grazing time or cropping rate, but they left feeding stations when their lateral neck angle reached a critical point suggesting a biokinetic explanation. Leaving feeding stations when ungrazed forage can no longer be reached and patches when intake rate drops both appeared to be rules used by wapiti grazing grasslands of the boreal mixed wood forest.
We tested the idea that ruminants allocate their feeding time to habitat patches in relation to foraging efficiency. We used five tame red deer (Cervus elaphus) in an enclosure planted with four treatment of timothy grass (Phleum pratense) differing in their stage of growth. Older swards offered higher biomass but lower nutritional quality than younger swards. We observed time spent feeding in each treatment during each of seven trials. We measured goodness-of-fit between observed times and predictions from two alternative hypotheses differing in optimization strategy (maximizing versus matching), and a third, null hypothesis. We tested the hypotheses using two alternative currecies: digestible protein, and digestible dry matter or energy. Although digestible protein concentration and dry-matter digestibility were highly correlated (r=0.763, PR
infPred
sup2
=0.899) across all animals and trials. The other hypotheses were rejected. The results have important ecological implications in showing the underlying role of food in the selection of habitat by ruminants, and that simple, mechanistic models of forage intake and digestion can be scaled up to the level of animal behavioural choices.
In this paper kernel methods for the nonparametric estimation of the utilization distribution from a random sample of locational observations made on an animal in its home range are described. They are of flexible form, thus can be used where simple parametric models are found to be inappropriate or difficult to specify. Two examples are given to illustrate the fixed and adaptive kernel approaches in data analysis and to compare the methods. Various choices for the smoothing parameter used in kernel methods are discussed. Since kernel methods give alternative approaches to the Anderson (1982) Fourier transform methods, some comparisons are made.
Researchers and managers undertaking wildlife habitat assessments commonly require spatially explicit environmental map layers such as those derived from forest inventory and remote sensing. However, end users of geospatial products must often make choices regarding the source and level of detail required for characterizing habitat elements, with few published resources available for guidance. We appraised three environmental data sources that represent options often available to researchers and managers in wildlife ecological studies: (i) a pre-existing forest inventory; (ii) a general-purpose, single-attribute remote sensing land cover map; and (iii) a specific-purpose, multi-attribute remote sensing database. The three information sources were evaluated with two complementary analyses: the first designed to appraise levels of map quality (assessed on the basis of accuracy, vagueness, completion, consistency, level of measurement, and detail) and the second designed to assess their relative capacity to explain patterns of grizzly bear (Ursus arctos) telemetry locations across a 100,000-km2 study area in west-central Alberta, Canada. We found the forest inventory database to be reasonably functional in its ability to support resource selection analysis in regions where coverage was available, but overall, the data suffered from quality issues related to completeness accuracy, and consistency. The general-purpose remote sensing land cover product ranked higher in terms of overall map quality, but demonstrated a lower capacity for explaining observed patterns of grizzly bear habitat use. We found the best results using the specific-purpose, multi-attribute remote sensing database, and recommend that similar information sources be used as the foundation for wildlife habitat studies whenever possible, particularly those involving large areas that span jurisdictional boundaries.