Home Range Overlap Research Articles

A mechanistic, stigmergy model of territory formation in solitary animals: Territorial behavior can dampen disease prevalencebut increase persistence.

Although movement ecology has leveraged models of home range formation to explore the effects of spatial heterogeneity and social cues on movement behavior, disease ecology has yet to integrate these potential drivers and mechanisms of contact behavior into a generalizable disease modeling framework. Here we ask how dynamic territory formation and maintenance might contribute to disease dynamics in a territorial, solitary predator for an indirectly transmitted pathogen. We developed a mechanistic individual-based model where stigmergy-the deposition of signals into the environment (e.g., scent marking, scraping)-dictates local movement choices and long-term territory formation, but also the risk of pathogen transmission. Based on a variable importance analysis, the length of the infectious period was the single most important variable in predicting outbreak success, maximum prevalence, and outbreak duration. Host density and rate of pathogen decay were also key predictors. We found that territoriality best reduced maximum prevalence in conditions where we would otherwise expect outbreaks to be most successful: slower recovery rates (i.e., longer infectious periods) and higher conspecific densities. However, for slower pathogen decay rates, stigmergy-driven movement increased outbreak durations relative to random movement simulations. Our findings therefore support a limited version of the "territoriality benefits" hypothesis-where reduced home range overlap leads to reduced opportunities for pathogen transmission, but with the caveat that reduction in outbreak severity may increase the likelihood of pathogen persistence. For longer infectious periods and higher host densities, key trade-offs emerged between the strength of pathogen load, the strength of the stigmergy cue, and the rate at which those two quantities decayed; this finding raises interesting questions about the evolutionary nature of these competing processes and the role of possible feedbacks between parasitism and territoriality. This work also highlights the importance of considering social cues as part of the movement landscape in order to better understand the consequences of individual behaviors on population level outcomes.

Mating system of Thrichomys fosteri in the Brazilian Pantanal: spatial patterns indicate promiscuity

Animal mating systems provide key insights into the relationship between evolutionary processes and ecological factors such as the spatio-temporal fluctuation of resource abundance. Characteristics of mating systems can be inferred from the spatial distribution of conspecifics and the arrangement of reproductive pairs. Here we used home-range size and overlap for Thrichomys fosteri in the Brazilian Pantanal to infer the mating system on this echimyid rodent. Our aims were to verify the existence of sexual dimorphism, to test whether home-range size varied with the sex and body weight of the individuals, to evaluate the degree of home-range overlap, to estimate mean population density, and to infer individuals’ mating system. Twenty one individuals (15 males and six females) were radio tracked from 14 to 349 days, with the number of locations by individuals ranging from 19 to 193 locations. There was a male-biased sexual dimorphism in body weight where males were 1.36 times heavier than females. Males’ home-range size increased with their body weight, while for females there was no relationship. There was extensive home-range overlap between both sexes, and no evidence of territoriality. Mean population density ranged from 0.9 to 3.03 individuals/ha. Our results indicate that multiple mates were available for both sexes, characterizing a promiscuous mating system.

Genetic relatedness cannot explain social preferences in black-and-white ruffed lemurs, Varecia variegata

Fission–fusion social dynamics are common among a number of vertebrate taxa, and yet the factors shaping these variable associations among subgroup members have not been widely addressed. Associations may occur simply because of shared habitat preferences; however, social ties may also be influenced by genetic relatedness (kinship) or social attraction. Here, we investigate the association patterns of wild black-and-white ruffed lemurs, Varecia variegata, in Ranomafana National Park, Madagascar using behavioural, spatial (home range) and genetic data from 24 individually identified animals. We collected 40 840 records of group composition over a 17-month period and from this calculated pairwise association indices. We also used ranging coordinates and genetic samples to estimate patterns of spatial overlap and kinship, and then related these measures to patterns of affiliation. From these analyses, we found that dyadic ruffed lemur social associations were generally sparse and weak, that home range overlap was minimal and that average relatedness within the community was low. We found no evidence that kinship was related to patterns of either spatial overlap or social association; instead, associations were primarily driven by space use. Moreover, social preferences were unrelated to kinship. While home range overlap explained most of the variation seen in social association, some variation remained unaccounted for, suggesting that other social, ecological and biological factors such as shared resource defence or communal breeding might also play a role in social attraction. Our results further highlight the need to consider individual space use and nuances of species behaviour when investigating social preference and social association more generally.

Siring success in kangaroos: size matters for those in the right place at the right time

Abstract In polygynous species, male reproductive success is predicted to be monopolized by a few dominant males. This prediction is often not supported, suggesting that ecological and alternative mating tactics influence siring success. The spatiotemporal distribution of individuals and the number of males competing for each receptive female are often overlooked because they are difficult to monitor in wild animals. We examined how spatial overlap of female–male pairs, the time spent by a male on the breeding site, number of competitors, and morphological traits influence siring probability in eastern gray kangaroos (Macropus giganteus). We compared home range overlap for 12 208 dam–male pairs and 295 known dam–sire pairs to define local competitive groups and to estimate every male’s opportunity to sire the young of each female. We compared models considering morphological traits relative to the entire population or to local competitive groups. Including local competition improved model performance because it estimated the intensity of competition and compared each male’s morphological traits to those of its competitive group. Regardless of size, males can increase their probability to sire a young by increasing their mating opportunity relative to the mother. We underline the importance of considering spatial structure to assess the intensity of competition in species where males cannot equally access all females in a population. The estimation of mating opportunity and intensity of local competition improves our understanding of how morphological traits affect siring success when each mating event involves a different set of competing males, a characteristic of most wild species.

Unsustainable anthropogenic mortality disrupts natal dispersal and promotes inbreeding in leopards.

Anthropogenic mortality of wildlife is typically inferred from measures of the absolute decline in population numbers. However, increasing evidence suggests that indirect demographic effects including changes to the age, sex, and social structure of populations, as well as the behavior of survivors, can profoundly impact population health and viability. Specifically, anthropogenic mortality of wildlife (especially when unsustainable) and fragmentation of the spatial distribution of individuals (home‐ranges) could disrupt natal dispersal mechanisms, with long‐term consequences to genetic structure, by compromising outbreeding behavior and gene flow. We investigate this threat in African leopards (Panthera pardus pardus), a polygynous felid with male‐biased natal dispersal. Using a combination of spatial (home‐range) and genetic (21 polymorphic microsatellites) data from 142 adult leopards, we contrast the structure of two South African populations with markedly different histories of anthropogenically linked mortality. Home‐range overlap, parentage assignment, and spatio‐genetic autocorrelation together show that historical exploitation of leopards in a recovering protected area has disrupted and reduced subadult male dispersal, thereby facilitating opportunistic male natal philopatry, with sons establishing territories closer to their mothers and sisters. The resultant kin‐clustering in males of this historically exploited population is comparable to that of females in a well‐protected reserve and has ultimately led to localized inbreeding. Our findings demonstrate novel evidence directly linking unsustainable anthropogenic mortality to inbreeding through disrupted dispersal in a large, solitary felid and expose the genetic consequences underlying this behavioral change. We therefore emphasize the importance of managing and mitigating the effects of unsustainable exploitation on local populations and increasing habitat fragmentation between contiguous protected areas by promoting in situ recovery and providing corridors of suitable habitat that maintain genetic connectivity.

Changes in spatial organization following an acute epizootic: Tasmanian devils and their transmissible cancer

Epidemiological studies commonly monitor host population density but rarely account for how transmission dynamics might be influenced by changes in spatial and social organization that arise from high mortality altering population demography. Devil facial tumour disease (DFTD), a novel transmissible cancer, caused almost 100% mortality of its single host, the Tasmanian devil, and a >90% local population decline since its emergence 20 years ago. We compare size and overlap in home ranges in a devil population before and 15 years after disease outbreak. We used location data collected with VHF tracking collars in 2001 and GPS collars in the same area in 2015 and 2016. Density of adult devils, calculated from live trapping data in the same years, show a strong decrease following the disease outbreak. The decline in density was accompanied by a reduction in female home range size, a trend not observed for males. Both spatially explicit population modelling and animal tracking showed a decrease in female home range overlap following the DFTD outbreak. These changes in spatial organisation of the host population have the potential to alter the local transmission dynamic of the tumours. Our results are consistent with the general theory of sex-biased spatial organization mediated by resource availability and highlight the importance of incorporating spatial ecology into epidemiological studies.

Fine-scale genetic structure in Lahille’s bottlenose dolphins (Tursiops truncatus gephyreus) is associated with social structure and feeding ecology

Varying levels of population structure may arise from interactions between intrinsic behavioral and demographic factors and extrinsic environmental factors. Social organization, habitat use, resource partitioning, or even individual preferences are putative drivers of population genetic differentiation over fine spatial scales. Here, genome-wide data from single-nucleotide polymorphisms (SNPs) and carbon and nitrogen stable isotope data were used to examine population structure and niche partitioning among three social units of bottlenose dolphins with strong home range overlap in a relatively small geographic area in southern Brazil. Results from model-based and model-free analyses of population structure supported the delineation of two populations, one with preferences for estuarine waters and another strictly coastal, consistent with isotopic niche differentiation. These findings suggest that genetic and ecological structuring is mainly driven by habitat use. At finer scale, we also detected low but significant genetic differentiation among the three social units. The outcomes of this study provide new insights into population structure of Lahille’s bottlenose dolphins in the Patos Lagoon estuary and its adjacent coastal waters, which are exposed to increasing levels of anthropogenic disturbances, such as intensive artisanal fisheries, pollution, and boat traffic. Although for demographic studies, the estuary and the coastal dolphins should be treated separately, for conservation purposes, we recommend that the three social units be regarded as different entities.

Do Monkeys Avoid Areas of Home Range Overlap Because They Are Dangerous? A Test of the Risk Hypothesis in White-Faced Capuchin Monkeys (Cebus capucinus)

In social animals, areas where the home ranges of neighboring groups overlap are often underused. The Risk Hypothesis posits that the costs of intergroup conflict create a “landscape of fear,” discouraging the use of such shared areas. To test this hypothesis, we observed the behavior of white-faced capuchins (Cebus capucinus) in central vs. peripheral areas of their home ranges. If capuchins perceive areas of home range overlap as “risky,” we predicted they would change activity budgets, vocalization rates, and foraging behavior in these areas. A spatially explicit behavioral comparison based on nearly 100 h of focal follows revealed that capuchins socialize less in the periphery (vs. the center) of their home range. Time spent resting, foraging, and engaging in vigilance, as well as vocalization rates, varied in consistent ways across all four study groups, but these differences did not reach statistical significance. Fruit trees near range borders (vs. the center) contained more ripe fruit, and groups spent more time in these trees, with more individuals entering to feed and consuming more fruits. However, capuchins did not alter their foraging behavior in potentially risky peripheral areas in a manner consistent with predictions of optimal foraging theory: intake rates at patch departure were not significantly lower and groups depleted trees to a greater extent along the periphery vs. in the center of their range. These results suggest that while peripheral areas are perceived as risky and this “landscape of fear” contributes to behavioral changes, they also provide resources whose value may outweigh the cost of intergroup encounters.

Investigating uneven recovery of repatriated bobcats (Lynx rufus) in a mined landscape: space use, habitat use and condition in coal country

Abstract ContextBobcats (Lynx rufus) were extirpated from Ohio, USA, during the mid-1800s. Genetic evidence indicates that they recolonised from neighbouring states. Initial re-establishment occurred almost simultaneously in two spatially distinct areas of a coal-mined landscape in the 1980s. Relative population growth was apparently higher in the eastern than in the southern area. AimsUnderstanding the reasons for the disparity in population dynamics and sustainability is essential for proper bobcat management. It also addresses substantial knowledge gaps in vertebrate carnivore ecology on mined land. We hypothesised that the characteristics of mined land in the eastern Ohio area provided bobcats with greater resources, enabling a more rapid recovery. MethodsWe trapped bobcats and took body measurements and weights to determine condition indices. We attached GPS radio-collars and used locations to determine annual home-range and core-area sizes, home-range and core-area overlap, and habitat selection using remotely sensed land cover data and mine permit records. We compared factors between the two bobcat population areas. Key resultsBody condition indices were higher, and home ranges and core areas of males and females were smaller, for eastern Ohio bobcats. Home-range overlap did not differ for any dyad type. Selection of mined land by habitat type differed at the home-range level, with eastern bobcats selecting more mined habitats and southern bobcats showing an opposite tendency. ConclusionsAn interaction may exist between landscape features of former surface mines and bobcat recovery. Results suggest more favourable habitat conditions in the eastern area, which featured more mined land and more older, less regulated mines, than in the southern area. These conditions may support a higher bobcat reproductive success. ImplicationsThe first bobcat harvest season in Ohio is under development by authorities. We recommend the regulation of eastern and southern Ohio as separate bobcat management units; the southern population should remain protected, and the eastern population should be managed conservatively as a source population to further colonise southern Ohio. Our data suggest that surface-mined land can be conducive to the restoration and conservation of species.

Space use by the giant anteater (Myrmecophaga tridactyla): a review and key directions for future research

Understanding the use of space is essential to promote effective conservation actions, particularly to xenarthran species that are threatened by habitat loss, poaching, and other environment degradation. Information regarding the use of space by the giant anteater (Myrmecophaga tridactyla), a large and vulnerable Neotropical mammal, is sparse and sometimes inconsistent in the scientific literature. Our aims are (1) to present an updated overview of giant anteater use of space; (2) to identify knowledge gaps; and (3) to recommend the next steps to advance this knowledge. We compiled information from 53 publications regarding the key aspects of space use: movement patterns, home range size and overlap, and habitat use. We identified the following research priorities: (a) the need of studies on different populations throughout the species’ range, including continuous native forest areas, and different spatial scales; (b) to develop research on dispersal by the individuals; (c) to understand movement patterns based on trajectory-related methods; (d) to comprehend home range overlap and territoriality ecological meaning; and (e) habitat selection and movement patterns on human-modified landscapes.

Spatial ecology of the giant armadillo Priodontes maximus in Midwestern Brazil

AbstractThe giant armadillo (Priodontes maximus) is the largest living armadillo. This naturally rare and poorly known species is endemic to South America and classified as “Vulnerable” by the IUCN. Here we explored aspects of the spatial ecology of P. maximus in Midwestern Brazil to gain insights on its ecology and biology to support conservation efforts. In 8 years, we identified 50 individuals of P. maximus and monitored 23 of them using telemetry methods. To characterize site fidelity and home range, we fitted individual continuous-time movement models and estimated Autocorrelated Kernel Density Estimates. We built a Structural Equation Model to evaluate how home-range area and daily displacement are related to each other, to sampling effort, and to individual characteristics. We estimated home-range overlap between pairs of different sexes using a bias-corrected Bhattacharyya coefficient. Finally, we formulated a canonical density estimation formula to characterize minimum population density. We gathered a total of 12,168 locations of P. maximus. The best-fitted movement models indicated site fidelity for all individuals and a median adult home-range area of 2,518 ha. Median adult daily displacement was 1,651 m. Home-range area scales positively with daily displacement and daily displacement scales positively with body mass. Median home-range overlap between pairs was low (4%) and adult females presented exclusive home ranges among themselves. Median minimum density was 7.65 individuals per 100 km2 (CI = 5.68–10.19 ind/100 km2). Our results are congruent with characterizing P. maximus as a generally asocial species, most likely promiscuous/polygynous, that establishes large, long-term home ranges, which grants the population a naturally low density. Spatial patterns and biological characteristics obtained in this study can be used to guide future conservation strategies for P. maximus in the Pantanal wetlands and elsewhere.

Effect of human activity on habitat selection in the endangered Barbary macaque

AbstractThe exponential growth of human population and infrastructure is significantly reducing the amount of ecological resources available for wild animals. We analyzed the effect of human activity on Barbary macaques Macaca sylvanus, an endangered species restricted to the fragmented forests of Morocco and Algeria, using location data from five social groups inhabiting Ifrane National Park, Morocco. We used a resource selection function to explore the effects of anthropogenic disturbance on macaque habitat selection, using nine natural, social, and anthropogenic disturbance variables as predictors. Forest cover, home range overlap, herding route proximity, and road proximity were all significant predictors of habitat use. Macaques avoided areas used by local shepherds, to reduce the risk of attack by shepherds’ dogs, but approached roads to increase the chances of provisioning by tourists. However, herding route and road use varied seasonally in line with levels of human use, suggesting that macaques may be navigating their environment strategically (in space and time) to balance food acquisition and risk avoidance. The results of this study highlight the importance of assessing human impact on habitat selection in both space and time. Our data on seasonal variations in macaques’ use of roads can help prevent road injuries, a major source of mortality for provisioned macaques, by focusing management efforts by national park workers in time and space. Furthermore, understanding when and where macaques seek provisioning from tourists can help combat provisioning, which negatively impacts macaque health, behavior, and susceptibility to poaching.

Spatial Use and Survival of Sympatric Populations of New England and Eastern Cottontails in Connecticut

Abstract The New England cottontail (NEC) Sylvilagus transitionalis is strongly associated with shrubland and early successional habitat and is the only cottontail native to the U.S. Northeast. The distribution and abundance of young forest habitat and NEC populations have declined. The eastern cottontail (EC) Sylvilagus floridanus was introduced into the U.S. Northeast in the early 1900s and uses similar habitat as NEC, but is expanding in distribution and abundance. Little information exists on spatial use, survival, and competition in sympatric populations of NEC and EC. Understanding differences in population demographics may identify important factors or relationships influencing population trends and aid in developing effective management strategies. Our objectives were to quantify home range and core area sizes, annual survival rates, minimum population densities, and range overlap for sympatric populations of NEC and EC at four sites in Connecticut. We monitored spatial use and survival rates of 107 radio-collared rabbits over a 10-y period. Mean annual home ranges and core areas were 10.9 and 2.5 ha for NEC and 5.6 and 1.6 ha for EC. Overlap in home range and core areas was greater within species than between species (NEC-EC). For both species and sex, home range size expanded from winter to breeding seasons. Survival rates were greater for NEC than for EC at all four sites, with predation as the major cause of mortality for both species. Space-use patterns suggest that the potential for EC to interfere with NEC reproduction is limited and avoidance or resource partitioning between species in the same patch may be occurring.

Movement seasonality in a desert-dwelling bat revealed by miniature GPS loggers

BackgroundBats are among the most successful desert mammals. Yet, our understanding of their spatio-temporal dynamics in habitat use associated with the seasonal oscillation of resources is still limited. In this study, we have employed state-of-the-art lightweight GPS loggers to track the yellow-winged bat Lavia frons in a desert in northern Kenya to investigate how seasonality in a desert affects the a) spatial and b) temporal dimensions of movements in a low-mobility bat.MethodsBats were tracked during April–May 2017 (rainy season) and January–February 2018 (dry season) using 1-g GPS loggers. Spatial and temporal dimensions of movements were quantified, respectively, as the home range and nightly activity patterns. We tested for differences between seasons to assess responses to seasonal drought. In addition, we quantified home range overlap between neighbouring individuals to investigate whether tracking data will be in accordance with previous reports on territoriality and social monogamy in L. frons.ResultsWe obtained data for 22 bats, 13 during the rainy and 9 during the dry season. Home ranges averaged 5.46 ± 11.04 ha and bats travelled a minimum distance of 99.69 ± 123.42 m/hour. During the dry season, home ranges were larger than in the rainy season, and bats exhibited high activity during most of the night. No apparent association with free water was identified during the dry season. The observed spatial organisation of home ranges supports previous observations that L. frons partitions the space into territories throughout the year.ConclusionsOur results suggest that, in low-mobility bats, a potential way to cope with seasonally harsh conditions and resource scarcity in deserts is to cover larger areas and increase time active, suggesting lower cost-efficiency of the foraging activity. Climate change may pose additional pressures on L. frons and other low-mobility species by further reducing food abundances.

Range overlap and spatiotemporal relationships of frugivorous lemurs at Kianjavato, Madagascar

Interspecific competition can strongly influence patterns of space use in animal communities, particularly between closely related species, and may be exacerbated in marginal habitat. This may be important in Madagascar, as lemurs face diminishing resources due to deforestation. We examined the range overlap and spatiotemporal relationships of three species of frugivorous lemur in the fragmented forests of Kianjavato, Madagascar. We conducted simultaneous location and behaviour sampling of black-and-white ruffed lemurs, Varecia variegata , red-fronted lemurs, Eulemur rufifrons , and red-bellied lemurs, Eulemur rubriventer , at two sites over a period of 11 months. We used Doncaster's index of dynamic interaction to investigate the relative amount of time species spent within 30 m and 100 m of each other, compared to the time expected based on random use of location points. All three species showed low core range overlap compared to home range overlap, and while core overlap was higher between interspecific groups than intraspecific groups, the difference was not substantial. Conversely, no spatiotemporal avoidance was observed, and red-fronted lemurs showed positive association (indicating possible attraction) with both red-bellied and ruffed lemurs. These positive spatiotemporal associations may be related to shared resource use in small forests, or predation avoidance strategies. At present, these species may rely more on spatial segregation and niche separation than spatiotemporal avoidance to minimize interspecific competition. • Frugivorous lemurs spatially avoid heterospecifics via low core range overlap. • Spatiotemporally, red-fronted lemurs associate positively with probable competitors. • Positive associations may result from shared limited resources or predators. • Spatial avoidance and niche differentiation may offset spatiotemporal overlap costs.

Life in the thornscrub: movement, home range, and territoriality of the reticulate collared lizard (Crotaphytus reticulatus)

ABSTRACTSeveral habitats may be required for an animal’s persistence, and movements within and among these habitats characterise an animal’s home range. For species of lizards, variation in home range size is typically best explained by either sit-and-wait or active foraging styles. In this study, we explore movements, home range size, and territoriality of Reticulate Collared Lizards (Crotaphytus reticulatus) from the typically sit-and-wait foraging subfamily Crotaphytinae. Over three years, we tracked 10 adult males and four adult females using GPS telemetry and found male C. reticulatus moved significantly longer distances and maintained significantly larger home ranges and core areas than females. We observed no home range overlap in females and one case of overlap in males, although all females maintained home ranges overlapped by a single male home range. The one-to-one pattern of a male home range overlapping just a single female home range is consistent with male mate guarding observed in active foragers. Moreover, compared to classic sit-and-wait foraging Common Collared Lizards (C. collaris), C. reticulatus moves more frequently, maintains a larger home range, is less territorial, and exhibits less sexual dimorphism; all traits of active foraging lizards. Indeed, C. reticulatus was observed actively stalking prey throughout its larger home range similar to G. wislizenii, which supports previous predictions regarding convergence in active foraging predatory behaviours between the species.

Habitat Use in a Population of the Northern Muriqui (Brachyteles hypoxanthus)

Habitat loss and fragmentation are known to restrict the movements of primates, including their ability to expand their home ranges. These effects are especially strong at high densities, where home range overlap can result in high rates of agonistic intergroup encounters over range defense. We investigated habitat use and range defense in a population of northern muriquis (Brachyteles hypoxanthus) at the Reserva Particular do Patrimonio Natural – Feliciano Miguel Abdala, in Minas Gerais, Brazil from August 2010 to July 2013. The four groups in this isolated population used 878 ha of forest, with home ranges exhibiting high interannual fidelity in location and low intergroup overlap. Core areas represented 13–29% of the respective home ranges and, except for one group, showed only moderate to low interannual fidelity in successive years. Of 130 intergroup encounters recorded in 2010–2011, significantly more occurred in core areas that overlapped with the range of another group than in areas of home range overlap or areas used exclusively by one group. Daily path lengths of the one group used in assessing range defensibility varied little (1075–1132 m) across years and relative to home range diameter did not meet the criteria for defensibility. However, the occurrence of independent subgroups, combined with a mean monthly detection distance of 242 m, provides strong evidence of range defensibility. These findings point to the importance of fission–fusion dynamics for intergroup range defense, particularly in primates living at high densities in fragmented habitats.

Space use patterns affect stable isotopes of polar bears (Ursus maritimus) in the Beaufort Sea

Space use patterns vary within a population and can influence diet composition of individuals. Within the Beaufort Sea, polar bears (Ursus maritimus) either use offshore areas and follow sea ice retreat (pelagic) or utilize nearshore areas (coastal), exposing individuals to different food sources. We examine the relationship between coastal and pelagic space use patterns and diet quantified by stable isotopes (δ15N and δ13C) of polar bears in the Beaufort Sea between 2007 and 2011. We examined spatial fidelity using home range overlap and assigned bears to one of two space use patterns (coastal or pelagic) based on proximity of home ranges to the coast. We estimated diet composition using inter- and intratissue variability in stable isotopes from hair and claws to examine seasonal shifts in diet. Sectioning of claws provided additional insights on diet, but guard hair sections did not. Polar bears showed spatial fidelity between years. Nitrogen stable isotopes were related to space use patterns. Coastal bears were 15N-depleted compared to pelagic bears due to coastal bears being enriched in 15N possibly from either scavenging on bowhead whale carcasses (Balaena mysticetus) killed during subsistence hunts or pelagic bears being nutritionally stressed. Although upper trophic level predators can provide insight into trophic dynamics and changes in ecosystem function, knowledge of space use patterns and foraging behavior is an important aspect of diet interpretation.

Habitats modified for tourism affect the movement patterns of an endemic marsupial, the Rottnest Island quokka (Setonix brachyurus)

The quokka (Setonix brachyurus), an iconic marsupial endemic to Western Australia, is listed as vulnerable. It is found at its greatest abundance on Rottnest Island, where little is known about its home range and movement patterns. We estimated the home ranges of 22 male and 23 female quokkas within each season in four habitat types on Rottnest Island: coastal dune, grass/heath, woodland and settlement areas developed for tourism. We also tested for factors affecting home range and space use. The mean seasonal home-range size of quokkas was 1.91 ± 0.23 ha, and there was no effect of sex or weight, habitat type or wet or dry periods on the size of the home ranges. Home-range overlap during both night and day was significantly lower in the settlement (25.9%), compared with costal dunes (78.5%), woodlands (70.3%) and grass/heath (66.6%). This was due to feeding and resting sites being spatially separated, with quokkas resting outside of the settled areas during the day and travelling back to these areas to feed at night. This research demonstrates how tourism development can impact on the behaviour and movement patterns of local species and will inform future management of the quokka on Rottnest Island.

Spatial ecology of river otters in a human-modified landscape

AbstractRiver otter populations have expanded across much of their historical range, including in Illinois where they were reintroduced from 1994 to 1997. These expanding populations are recolonizing a wide range of landscapes with different levels of human modification, which could influence how river otters use space in relation to habitat characteristics and each other. Our objectives were to quantify 1) home ranges and core areas, 2) sociality, and 3) habitat selection across all available habitats and within home ranges (second- and third-order selection, respectively) of 22 radiomarked river otters (Lontra canadensis) in southern Illinois during 2014–2016. Our study area contained a diverse mix of forest, agriculture, aquatic and wetland habitats, and a range of urban development intensity. We examined sociality using the frequency at which individuals were located < 25 m from a conspecific and compared home-range overlap among individuals based on sex. Habitat selection at the second and third order was analyzed using an eigen-analysis of selection ratios based on landcover categories. Similar to other studies, male river otters had > 2-fold larger home ranges and core areas than females in southern Illinois. Several lines of evidence indicated males were more social than females. Males were located close to a conspecific more frequently than were females, and overlap of home ranges and core areas among males was greater than it was among females or between sexes. As observed in other landscapes, river otters strongly selected herbaceous and wooded wetlands at both second- and third-order scales. River otters selected terrestrial cover types with vegetative cover potentially due to shelter or prey availability. Forests were selected over crop fields at the third-order scale, which was consistent with studies using sign surveys. River otters in our study had home ranges containing 0–40% developed land cover, but we found no evidence that otters living in more developed areas used their home ranges more selectively. River otters in this landscape were plastic in regard to social behavior and habitat selection, highlighting their generalist nature and providing insight into their ability to successfully recolonize areas of the Midwest with sufficient vegetative cover and aquatic habitat, among other factors.