Philip D. McLoughlin

Intraspecific Variation in Home Range Overlap with Habitat Quality: A Comparison among Brown Bear Populations

We developed a conceptual model of spatial organization in vertebrates based upon changes in home range overlap with habitat quality. We tested the model using estimates of annual home ranges of adult females and densities for 30 populations of brown bears (Ursus arctos) in North America. We used seasonality as a surrogate of habitat quality, measured as the coefficient of variation among monthly actual evapotranspiration values for areas in which study populations were located. We calculated home range overlap for each population as the product of the average home range size for adult females and the estimated population density of adult females. Home range size varied positively with seasonality; however, home range overlap varied with seasonality in a nonlinear manner. Areas of low and high seasonality supported brown bears with considerable home range overlap, but areas of moderate seasonality supported brown bears with low home range overlap. These results are consistent with behavioural theory predicting a nonlinear relationship between food availability and territoriality.

Declines in populations of woodland caribou

We summarize the demography of woodland caribou (Rangifer tarandus caribou) inhabiting 6 ranges in northeast Alberta, Canada, from 1993 to 2002. Among ranges, mean annual survival of radiomarked adult females averaged 0.88 (range: 0.86-0.93). Predation by wolves (Canis lupus) and other predators was implicated as the most common cause of death for adult caribou in northeast Alberta. Pregnancy rates (90-100%) and calf production (75-95%) were relatively high in all caribou ranges; however, mean annual recruitment was near or below 20 calves per 100 cows in most ranges (x = 17.1, range = 11.4-22.7). Caribou populations in 3 ranges have declined at average rates exceeding those that would lead to a 50% decline from initial population size over 3 generations; another population is declining at half this rate. Populations of caribou in 2 ranges appear to be stable, declining marginally since inception of our study. The current distribution, intensity, amount, and type of human activity in and near caribou ranges is likely compromising the integrity of caribou habitat. Treatment of declines will require new land-use guidelines that promote caribou conservation.

A hierarchical pattern of limiting factors helps explain variation in home range size

Abstract Home range size characterizes the interplay between an organism and its environment. Determinants of home range size can be intrinsic or extrinsic to the individual but all factors relate along a hierarchical pattern according to spatial and temporal scale. Determinants of home range size at species and population levels result from relatively slow processes, such as evolutionary changes in body size or global changes in climate. Range determinants at the lower level of individuals, however, can change at a relatively fast rate as they result from more rapid processes, such as the seasonal production of food or annual changes in predation rates. Not only do higher scales constrain those below but also lower level processes combine to affect higher scales. Further, correlates of home range size can differ among scales. To incorporate the possible findings of different patterns at different temporal and spatial scales we recommend using a comparative approach to complement controlled manipulative experiments.

Considering ecological dynamics in resource selection functions.

1. Describing distribution and abundance is requisite to exploring interactions between organisms and their environment. Recently, the resource selection function (RSF) has emerged to replace many of the statistical procedures used to quantify resource selection by animals. 2. A RSF is defined by characteristics measured on resource units such that its value for a unit is proportional to the probability of that unit being used by an organism. It is solved using a variety of techniques, particularly the binomial generalized linear model. 3. Observing dynamics in a RSF - obtaining substantially different functions at different times or places for the same species - alerts us to the varying ecological processes that underlie resource selection. 4. We believe that there is a need for us to reacquaint ourselves with ecological theory when interpreting RSF models. We outline a suite of factors likely to govern ecologically based variation in a RSF. In particular, we draw attention to competition and density-dependent habitat selection, the role of predation, longitudinal changes in resource availability and functional responses in resource use. 5. How best to incorporate governing factors in a RSF is currently in a state of development; however, we see promise in the inclusion of random as well as fixed effects in resource selection models, and matched case-control logistic regression. 6. Investigating the basis of ecological dynamics in a RSF will allow us to develop more robust models when applied to forecasting the spatial distribution of animals. It may also further our understanding of the relative importance of ecological interactions on the distribution and abundance of species.

Lifetime reproductive success and density- dependent, multi-variable resource selection

Individuals are predicted to maximize lifetime reproductive success (LRS) through selective use of resources; however, a wide range of ecological and social processes may prevent individuals from always using the highest-quality resources available. Resource selection functions (RSFs) estimate the relative amount of time an individual spends using a resource as a function of the proportional availability of that resource. We quantified the association between LRS and coefficients of individual-based RSFs describing lifetime resource selection for 267 female red deer (Cervus elaphus) of the Isle of Rum, Scotland, from 1970 to 2001. LRS was significantly related to first- and second-order effects of selection for Agrostis/Festuca grassland and proximity to the sea coast (quality of forage within Agrostis/Festuca grassland was highest nearest the coast (ratio of short : long grassland)). The benefits of selecting for quality in Agrostis/Festuca grassland, however, traded-off with increases in LRS gained by avoiding conspecific density. LRS was inversely associated with local density, which was highest along the coast, and reproductive benefits of selecting Agrostis/Festuca grassland diminished with increasing density. We discuss the relevance of these results to our understanding of the spatial distribution of red deer abundance, and potential applications of our approach to evolutionary and applied ecology.

HIERARCHICAL HABITAT SELECTION BY TUNDRA WOLVES

Abstract Using resource selection functions, we examined habitat selection patterns of tundra wolves (Canis lupus) in the central Canadian Arctic at the level of the home range and within the home range. Esker habitat was relatively preferred by wolves at the home range level of selection, possibly indicating the importance of denning habitat as a limiting factor for tundra wolves. We failed to conclusively tie vegetation communities to movements of wolves within the home range. Eskers make up only about 1–2% of the landscape; hence, a potential conflict between wolf conservation and industrial development in the region may occur as eskers are targeted as a source of granular material for road construction. Results of this study underline the importance of scale dependence in habitat selection. Failure to view habitat selection as a hierarchical process may result in a narrow and possibly misleading notion of the value of habitats to animals.

Maternal and individual effects in selection of bed sites and their consequences for fawn survival at different spatial scales

We examined the relationship between survival of roe deer (Capreolus capreolus) fawns at Trois Fontaines, Champagne-Ardennes, France, and factors related to bed-site selection (predator avoidance and thermoregulation) and maternal food resources (forage availability in the maternal home range). Previous studies have demonstrated that at small scales, the young of large herbivores select bed sites independently from their mothers, although this selection takes place within the limits of their mother’s home range. Fawn survival was influenced largely by the availability of good bed sites within the maternal home range, not by the fawn’s selection of bed sites; however, selection for thermal cover when selecting bed sites positively influenced survival of young fawns. Typical features of a good home range included close proximity to habitat edges, which is related to forage accessibility for roe deer. The availability of bed sites changed as fawns aged, probably due to an increased mobility of the fawn or a different use of the home range by the mother; sites offering high concealment and thermal protection became less available in favor of areas with higher forage accessibility. Despite the minor influence of bed-site selection on survival, roe deer fawns strongly selected their bed sites according to several environmental factors linked to predator avoidance and thermoregulation. Fawns selected for sites providing concealment, light penetration, and avoided signs of wild boar (Sus scrofa) activity. Avoidance of sites with high light penetration by young fawns positively affected their survival, confirming a negative effect on thermoregulation due to reduced thermal cover. Selection for light penetration by older fawns was less clear. We discuss these results in the context of cross-generational effects in habitat selection across multiple scales, and the potential influence of the ‘ghost of predation past’.

Increasing density leads to generalization in both coarse‐grained habitat selection and fine‐grained resource selection in a large mammal

Density is a fundamental driver of many ecological processes including habitat selection. Theory on density-dependent habitat selection predicts that animals should be distributed relative to profitability of habitat, resulting in reduced specialization in selection (i.e. generalization) as density increases and competition intensifies. Despite mounting empirical support for density-dependent habitat selection using isodars to describe coarse-grained (interhabitat) animal movements, we know little of how density affects fine-grained resource selection of animals within habitats [e.g. using resource selection functions (RSFs)]. Using isodars and RSFs, we tested whether density simultaneously modified habitat selection and within-habitat resource selection in a rapidly growing population of feral horses (Equus ferus caballus Linnaeus; Sable Island, Nova Scotia, Canada; 42% increase in population size from 2008 to 2012). Among three heterogeneous habitat zones on Sable Island describing population clusters distributed along a west-east resource gradient (west-central-east), isodars revealed that horses used available habitat in a density-dependent manner. Intercepts and slopes of isodars demonstrated a pattern of habitat selection that first favoured the west, which generalized to include central and east habitats with increasing population size consistent with our understanding of habitat quality on Sable Island. Resource selection functions revealed that horses selected for vegetation associations similarly at two scales of extent (total island and within-habitat zone). When densities were locally low, horses were able to select for sites of the most productive forage (grasslands) relative to those of poorer quality. However, as local carrying capacity was approached, selection for the best of available forage types weakened while selection for lower-quality vegetation increased (and eventually exceeded that of grasslands). Isodars can effectively describe coarse-grained habitat selection in large mammals. Our study also shows that the main predictions of density-dependent habitat selection are highly relevant to our interpretation of RSFs in space and time. At low but not necessarily high population size, density will be a leading indicator of habitat quality. Fitness maximization from specialist vs. generalist strategies of habitat and resource selection may well be apparent at multiple spatial extents and grains of resolution.

Habitat selection and tHe evolution of specialists in Heterogeneous environments

Recent advances in studies of habitat selection and resource use provide a framework not only for estimating resource specialization, but also for predicting future success of specialist and generalist strategies. The protocol merges resource selection functions with fitness and population dynamics to assess the evolution of competing strategies that change with density-dependent habitat selection. These strategies are revealed by resource selection coefficients derived from marked individuals that can then be used to predict each individual’s fitness at different population sizes. Simulated consumer resource dynamics confirm the theory’s ability to identify strategies of habitat and resource use with simple statistical models that summarize rather complex systems. The theory produces excellent fits with simulated data when strategies depend on density, and when the success of a single strategy interacts with others. Specialist strategies yield highest fitness at low population density, whereas generalists have highest fitness in dense populations. When applied to female red deer living on the Isle of Rum, Scotland, the theory correctly predicts an equilibrium distribution of competing strategies dominated by specialization on Agrostis/Festuca grassland. Specialization declined as population density increased through time. Simultaneously, changes in the genetic structure of the population reflected the increased opportunity for out

Lichen abundance in the peatlands of northern Alberta: Implications for boreal caribou 1

ABSTRACT In boreal forests, wildfire is a dominant ecological process that, among other things, affects the distribution and abundance of terrestrial lichens. Woodland caribou (Rangifer tarandus caribou) occupying peatland complexes of western Canada rely on terrestrial lichens for winter forage. Understanding the relationship between lichen distribution and fire is therefore important in order to understand caribou ecology. We documented abundance of terrestrial lichens in 73 peatland sites in northern Alberta, all within caribou home ranges. Forty-eight of these had been disturbed by forest fire within the past 70 y, while 25 had not been disturbed for at least 70 y. Peatlands that had not been disturbed for at least 70 y had low lichen cover (average 21.7 ±2.1%; range 4.6–54.0%) and lower lichen biomass (660.0 ±63.3 kg ·ha−1) than other studied boreal areas. However, lichen in sites disturbed by fire appeared to have recovered after only 40 y. This rapid recovery seems to have been mediated by a high growth rate: 4.8 ± 0.1 mm·y−1. Controlling for the effect of time since fire, lichen cover was inversely related to cover of Sphagnumspp., while growth rates of lichen were positively related to time since fire. Although the re-growth of lichen after fire was rapid in comparison to other systems, we suggest that fire has a strong effect on lichen distribution and hence on the spatial distribution of foraging habitat for Alberta caribou.