John F. Benson

Regulation of space use in a solitary felid: population density or prey availability?

Home range size in birds and mammals appears to be influenced by a number of factors including food availability, body mass and population density. However, few studies have convincingly shown population density to influence the extent of space use in a population of free-ranging carnivores without a corresponding increase in food availability. We investigated the relative effects of food availability, body weight and increased density on the size of adult bobcat, Lynx rufus, home ranges and core areas in Mississippi, U.S.A. during 1989–1997. We observed an increase in population density and a decrease in annual mean home range and core area sizes for males and females during this 9-year study. Population density explained 64% and 56% of the variation in home range size for males and females, respectively, whereas food availability and body weight failed to explain the observed reduction in bobcat home range size. Population density was also the most important variable explaining variation in core areas for both sexes, although food availability also appeared to contribute to variation, especially for females. We suggest that population density should be considered along with energy acquisition and metabolic factors such as food availability and body size when investigating variability in home range and core area sizes of mammals.

Space Use and Habitat Selection by Female Louisiana Black Bears in the Tensas River Basin of Louisiana

Abstract Studies of space use and habitat selection of endangered species are useful for identifying factors that influence fitness of individuals and viability of populations. However, there is a lack of published information regarding these behaviors for the federally threatened Louisiana black bear (Ursus americanus luteolus). We documented space use and habitat selection for 28 female black bears in 2 subpopulations of the Tensas River Basin population in northeast Louisiana, USA. The Tensas subpopulation inhabits a relatively large (>300-km2) contiguous area of bottomland hardwood forest, whereas the Deltic subpopulation exists mainly in 2 small (<7-km2) forested patches surrounded by an agricultural matrix. Females on Deltic maintained smaller seasonal and annual home ranges than females on Tensas (all P < 0.04), except for females with cubs during spring. On Tensas, females with cubs maintained smaller home ranges than females without cubs during spring (P = 0.01), but we did not detect this difference on Deltic or in other seasons. Females on Tensas and Deltic exhibited differences in habitat selection when establishing home ranges and within home ranges (P < 0.001). Deltic females selected mature bottomland hardwood forests and avoided agricultural habitats at both spatial scales. Tensas females selected a mixture of swamps, mature and regenerating forests, and exhibited variation in selection across scale, season, and reproductive status. We suggest that differences in space use and habitat selection between Tensas and Deltic are at least partially due to habitat differences at the landscape (i.e., amount of forested habitat) and patch (i.e., food availability) scales. Our results contribute to the understanding of factors that influence space use and habitat selection by black bears and provide specific information on habitat types selected by Louisiana black bears to agencies involved in habitat protection and restoration for this threatened subspecies.

Spatial genetic and morphologic structure of wolves and coyotes in relation to environmental heterogeneity in a Canis hybrid zone

Eastern wolves have hybridized extensively with coyotes and gray wolves and are listed as a ‘species of special concern’ in Canada. However, a distinct population of eastern wolves has been identified in Algonquin Provincial Park (APP) in Ontario. Previous studies of the diverse Canis hybrid zone adjacent to APP have not linked genetic analysis with field data to investigate genotype‐specific morphology or determine how resident animals of different ancestry are distributed across the landscape in relation to heterogeneous environmental conditions. Accordingly, we studied resident wolves and coyotes in and adjacent to APP to identify distinct Canis types, clarify the extent of the APP eastern wolf population beyond the park boundaries and investigate fine‐scale spatial genetic structure and landscape–genotype associations in the hybrid zone. We documented three genetically distinct Canis types within the APP region that also differed morphologically, corresponding to putative gray wolves, eastern wolves and coyotes. We also documented a substantial number of hybrid individuals (36%) that were admixed between 2 or 3 of the Canis types. Breeding eastern wolves were less common outside of APP, but occurred in some unprotected areas where they were sympatric with a diverse combination of coyotes, gray wolves and hybrids. We found significant spatial genetic structure and identified a steep cline extending west from APP where the dominant genotype shifted abruptly from eastern wolves to coyotes and hybrids. The genotypic pattern to the south and northwest was a more complex mosaic of alternating genotypes. We modelled genetic ancestry in response to prey availability and human disturbance and found that individuals with greater wolf ancestry occupied areas of higher moose density and fewer roads. Our results clarify the structure of the Canis hybrid zone adjacent to APP and provide unique insight into environmental conditions influencing hybridization dynamics between wolves and coyotes.

Florida Panther Habitat Selection Analysis of Concurrent GPS and VHF Telemetry Data

Abstract Florida panthers (Puma concolor coryi) are listed as an endangered subspecies in the United States and they exist in a single Florida population with <100 individuals; all known reproduction occurs south of Lake Okeechobee. Habitat loss is the biggest threat to this small population and previous studies of habitat selection have relied on very high frequency (VHF) telemetry data collected almost exclusively during diurnal periods. We investigated habitat selection of 12 panthers in the northern portion of the breeding range using 1) Global Positioning System (GPS) telemetry data collected during nocturnal and diurnal periods and 2) VHF telemetry data collected only during diurnal periods. Analysis of both types of telemetry data yielded similar results as panthers selected upland (P < 0.001) and wetland (P < 0.001) forested habitat types. Our results indicated that forests are the habitats selected by panthers and generally support the current United States Fish and Wildlife Service panther habitat ranking system. We suggest that future studies with greater numbers of panthers should investigate panther habitat selection using GPS telemetry data collected throughout the range of the Florida panther and with location attempts scheduled more evenly across the diel period. Global Positioning System radiocollars were effective at obtaining previously unavailable nocturnal telemetry data on panthers; however, we recommend that panther researchers continue to collect VHF telemetry data until acquisition rates and durability of GPS collars improve.

Intentional genetic introgression influences survival of adults and subadults in a small, inbred felid population

1. Inbreeding and low genetic diversity can cause reductions in individual fitness and increase extinction risk in animal populations. Intentional introgression, achieved by releasing genetically diverse individuals into inbred populations, has been used as a conservation tool to improve demographic performance in endangered populations. 2. By the 1980s, Florida panthers (Puma concolor coryi) had been reduced to a small, inbred population that appeared to be on the brink of extinction. In 1995, female pumas from Texas (P. c. stanleyana) were released in occupied panther range as part of an intentional introgression programme to restore genetic variability and improve demographic performance of panthers. 3. We used 25 years (1981-2006) of continuous radiotelemetry and genetic data to estimate and model subadult and adult panther survival and cause-specific mortality to provide rigorous sex and age class-specific survival estimates and evaluate the effect of the introgression programme on these parameters. 4. Genetic ancestry influenced annual survival of subadults and adults after introgression, as F(1) generation admixed panthers ( = 0·98) survived better than pre-introgression type panthers ( = 0·77) and other admixed individuals ( = 0·82). Furthermore, heterozygosity was higher for admixed panthers relative to pre-introgression type panthers and positively influenced survival. 5. Our results are consistent with hybrid vigour; however, extrinsic factors such as low density of males in some areas of panther range may also have contributed to higher survival of F(1) panthers. Regardless, improved survival of F(1) subadults and adults likely contributed to the numerical increase in panthers following introgression, and our results indicate that intentional admixture, achieved here by releasing individuals from another population, appears to have been successful in improving demographic performance in this highly endangered population.

Natal Den Selection by Florida Panthers

Abstract Information regarding habitat types selected by federally endangered Florida panthers (Puma concolor coryi) at natal den sites is needed because habitats used for parturition and kitten rearing potentially influence fitness of individuals and viability of the population. We located 51 natal den sites of 30 female panthers and performed a Euclidean distance analysis to determine which habitat types were selected and avoided at dens in south Florida, USA. Panther dens were closer to upland hardwoods, pinelands, and mixed wet forests (P ≤ 0.003) and farther from freshwater marsh–wet prairie (P = 0.009). We recommend that habitat protection efforts prioritize blocks of land that have abundant patches of upland hardwood, pinelands, and mixed wet forests to maintain preferred panther denning habitat.

Food Habits of Louisiana Black Bears (Ursus americanus luteolus) in Two Subpopulations of the Tensas River Basin

Abstract The Louisiana black bear (Ursus americanus luteolus) is listed federally as a threatened subspecies and current information about food habits is necessary for developing a sound conservation strategy. We collected and analyzed 251 scats from bears in the Tensas River Basin (TRB) population in northeast Louisiana. We compared diets of the two subpopulations (Tensas and Deltic) of the TRB and we observed differences during summer and fall. We suggest that the greater diversity of mast consumed by bears on Deltic may provide demographic stability to this small isolated subpopulation. Across the TRB, corn (Zea mays) made up the greatest percentage volume of scats and dominated summer and fall diet, whereas beetles (Coleoptera) were the food item found most frequently in scats. Other important food items included: blackberries and dewberries (Rubus spp.), acorns (Quercus spp.), palmetto fruit (Sabal minor), grasses/sedges (Poaceae or Cyperaceae), herbaceous vegetation and other species of soft mast.

A protected area influences genotype‐specific survival and the structure of a Canis hybrid zone

It is widely recognized that protected areas can strongly influence ecological systems and that hybridization is an important conservation issue. However, previous studies have not explicitly considered the influence of protected areas on hybridization dynamics. Eastern wolves are a species of special concern and their distribution is largely restricted to a protected population in Algonquin Provincial Park (APP), Ontario, Canada, where they are the numerically dominant canid. We studied intrinsic and extrinsic factors influencing survival and cause-specific mortality of hybrid and parental canids in the three-species hybrid zone between eastern wolves, eastern coyotes, and gray wolves in and adjacent to APP. Mortality risk for eastern wolves in areas adjacent to APP was significantly higher than for other sympatric Canis types outside of APP, and for eastern wolves and other canids within APP. Outside of APP, the annual mortality rate of all canids by harvest (24%) was higher than for other causes of death (4-7%). Furthermore, eastern wolves (hazard ratio = 3.5) and nonresidents (transients and dispersing animals, hazard ratio = 2.7) were more likely to die from harvest relative to other Canis types and residents, respectively. Thus, eastern wolves dispersing from APP were especially vulnerable to harvest mortality. For residents, eastern wolf survival was more negatively influenced by increased road density than for other Canis types, further highlighting the sensitivity of eastern wolves to human disturbance. A cycle of dispersal from APP followed by high rates of mortality and hybridization appears to maintain eastern wolves at low density adjacent to APP, limiting the potential for expansion beyond the protected area. However, high survival and numerical dominance of eastern wolves within APP suggest that protected areas can allow rare hybridizing species to persist even if their demographic performance is compromised and barriers to hybridization are largely absent in the adjacent matrix.

Space use, survival, movements, and reproduction of reintroduced louisiana black bears

Abstract Studies of reintroduced animals are beneficial to evaluate the success of reintroduction programs and to understand factors influencing fitness of reintroduced individuals. The geographic distribution of the federally threatened Louisiana black bear (Ursus americanus luteolus) has been reduced to 3 isolated populations due to habitat loss and excessive harvest. We reintroduced 23 adult female Louisiana black bears and their cubs to east-central Louisiana, USA, and documented postrelease space use, survival, movements, and reproduction. Individual females used larger home ranges after reintroduction than they had in the source population (P = 0.037). Spring ranges of reintroduced females were smaller than summer, autumn, and annual ranges (all P < 0.09), which did not differ from each other (all P > 0.60). Survival of reintroduced females did not differ between their first (S = 0.933) and second (S = 1.00) year after release or from annual survival of females in the source population (S = 0.964–1.00). Mean straight-line distance traveled by females from their release sites to the center of established home ranges or last recorded locations was 22.7 km. Six females reproduced after reintroduction and produced 15 cubs. Mean postrelease litter size of parturient reintroduced females (2.5) was similar to reported mean litter size of females in the source population (2.4). Our results suggest that the Louisiana reintroduction program is proceeding favorably; however, future studies should continue to monitor survival and reproduction of reintroduced females in Louisiana. Additional demographic parameters (i.e., cub survival) should be estimated to allow for population viability analysis to determine if the new population is self-sustaining.

Land Tenure and Occupation of Vacant Home Ranges by Bobcats (Lynx rufus)

Abstract Bobcat (Lynx rufus) social organization has been studied extensively, and a land tenure system based on prior residence appears to influence home range selection and maintenance. However, few studies have presented information about home range vacancies and the pattern of replacement by other bobcats. We documented 10 cases in which home ranges of deceased male and female resident bobcats were filled by transient or neighboring bobcats, and quantified the extent to which home ranges of new bobcats were similar to those of prior residents. For males (n = 5) and females (n = 5), respectively, an average of 85% and 79% of each replacements home range and 89% and 74% of their point locations overlapped with the former residents home range. This extensive overlap suggests that a land tenure system exists for bobcats and that home range vacancies are filled by transients or neighboring residents of the same sex. Although our results generally support the land tenure concept, we suggest that bobcat social organization may be more complex than previously reported.