Gail M. Blundell

LINEAR HOME RANGES: EFFECTS OF SMOOTHING, SAMPLE SIZE, AND AUTOCORRELATION ON KERNEL ESTIMATES

Simulations are necessary to assess the performance of home-range estimators because the true distribution of empirical data is unknown, but we must question whether that performance applies to empirical data. Some studies have used empirically based simulations, randomly selecting subsets of data to evaluate estimator performance, but animals do not move randomly within a home range. We created an empirically based simulation using a behavioral model, generated a probability distribution from those data, and randomly selected locations from that distribution in a chronological sequence as the simulated individual moved through its home range. Thus, we examined the influence of temporal patterns of space use and determined the effects of smoothing, number of locations, and autocorrelation on kernel estimates. Additionally, home-range estimators were designed to evaluate species that use space with few restrictions, traveling almost anywhere on the landscape. Many species, however, confine their movements ...

Characteristics of sex-biased dispersal and gene flow in coastal river otters: implications for natural recolonization of extirpated populations

River otters (Lontra canadensis) were extirpated from much of their historic distribution because of exposure to pollution and urbanization, resulting in expansive reintroduction programmes that continue today for this and other species of otters worldwide. Bioaccumulation of toxins negatively affects fecundity among mustelids, but high vagility and different dispersal distances between genders may permit otter populations to recover from extirpation caused by localized environmental pollution. Without understanding the influence of factors such as social structure and sex‐biased dispersal on genetic variation and gene flow among populations, effects of local extirpation and the potential for natural recolonization (i.e. the need for translocations) cannot be assessed. We studied gene flow among seven study areas for river otters (n = 110 otters) inhabiting marine environments in Prince William Sound, Alaska, USA. Using nine DNA microsatellite markers and assignment tests, we calculated immigration rates and dispersal distances and tested for isolation by distance. In addition, we radiotracked 55 individuals in three areas to determine characteristics of dispersal. Gender differences in sociality and spatial relationships resulted in different dispersal distances. Male river otters had greater gene flow among close populations (within 16–30 km) mostly via breeding dispersal, but both genders exhibited an equal, low probability of natal dispersal; and some females dispersed 60–90 km. These data, obtained in a coastal environment without anthropogenic barriers to dispersal (e.g. habitat fragmentation or urbanization), may serve as baseline data for predicting dispersal under optimal conditions. Our data may indicate that natural recolonization of coastal river otters following local extirpation could be a slow process because of low dispersal among females, and recolonization may be substantially delayed unless viable populations occurred nearby. Because of significant isolation by distance for male otters and low gene flow for females, translocations should be undertaken with caution to help preserve genetic diversity in this species.

Communication in river otters: Creation of variable resource sheds for terrestrial communities

Movements and behavior of animals can result in transfer of nutrients between discrete spatial patches, leading to spatial and temporal variability in resource sheds, modification of nutrient cycling, changes in productivity and in community structure and function, and increases in landscape heterogeneity. In this study, we explored the function of scent-marking at latrines by coastal river otters (Lontra canadensis), through investigating spatial distributions of otters with respect to gender, sociality, and the distribution of their food resources. We then calculated the amounts of nitrogen (N) and phosphorus (P) transported to latrine sites based on otter foraging behavior and the function of scent-marking at latrines. Locations of 55 radio-tagged otters in Prince William Sound, Alaska, USA, were obtained through aerial telemetry over a period of four years. Data on fish densities and marine habitat features were concurrently obtained from scuba transects and aerial surveys. A plastic social organizati...

Assessing sexual segregation in deer

Sexual segregation in temperate and arctic ruminants is defined as the differential use of space by the sexes outside the mating season. This phenomenon is widespread among taxa, and is especially prevalent among sexually dimorphic deer (Cervidae). Understanding how different genders are distributed across the landscape and how to assess these spatial patterns is of theoretical and applied importance. We developed a simple model to evaluate effects of landscape grain (i.e., patch characteristics), sampling scale, and population density of deer on detection of sexual segregation. We created landscape maps of 2 areas in which landscape grain was changed while other landscape metrics (e.g., area, shape, and diversity) were held relatively constant. We created a high-density population of deer to emulate conditions near ecological carrying capacity (K), and a low-density population at <K/2. Sexes of deer were assigned to 4 habitats based on differences in habitat selection derived from an ideal-free distribution, which created spatial separation of the sexes similar to observations in empirical studies. We sampled this pattern of sexual segregation for both areas at large and small scales of measurement using quadrats arranged systematically. We also compared the degree of sexual segregation for the coarse-grained landscape, where the sexes used habitats differently, with a null model in which habitat preferences were identical for each gender of deer. The null model emulated conditions during rut when the sexes were aggregated. Sexual segregation was significantly greater where habitat use differed between sexes, indicating that our model was correct and that the degree of spatial segregation was not an artifact of patch configuration, sampling scale, or population density. Logistic regression revealed that population density and the size of the sample unit significantly affected our ability to assess differences in the spatial distributions of male and female deer where differential use of habitats occurred. Variation in landscape grain, however, did not influence the detection of sexual segregation. Results from our model emphasize the importance of evaluating effects of population density and especially sampling scale on assessing spatial separation of the sexes. Failure to do so may result in not recognizing patterns of sexual segregation on the landscape, or in misinterpreting that phenomenon, which clearly holds consequences for those managing large herbivores or their habitats.

Post-release survival of river otters: Effects of exposure to crude oil and captivity

Few data exist on post-release survival of rehabilitated oiled wildlife, fueling the controversy surrounding wildlife rehabilitation efforts following oil spills. In 1998, we initiated a captive study to assess the effects of exposure to crude oil on physiological and behavioral processes in coastal river otters (Lontra canadensis). This study provided the opportunity to explore the effects of oiling and rehabilitation separately from those of captivity by comparing post-release survival rates of control and oiled river otters held in captivity with those of wild free-ranging otters. Fifteen wild-caught male river otters were assigned to 3 groups, of which 2 were given weathered crude oil in food (i.e., control, low dose, high dose) under controlled conditions at the Alaska Sealife Center. At the end of the rehabilitation period, animals were surgically implanted with radiotransmitters and released at the original site of capture or at an adjacent site in Prince William Sound, Alaska, USA. Concurrently, survival of 55 coastal river otters radiotagged in the wild was monitored in the same geographical area. Our results indicated that the captive, newly released animals (i.e., experimental otters) had a significantly lower survival rate than wild animals. We found no effect from exposure to hydrocarbons once rehabilitation was accomplished, but noted that lower levels of hemoglobin (a likely condition of rehabilitated oiled wildlife) were negatively correlated with survival and likely resulted in death from starvation. Therefore, rehabilitation may be a viable option for animals that have the potential for full recovery. We detected no relationship between location of release or estimated age of the experimental animals and their subsequent survival, although these results may be an artifact of small sample sizes. We recommend that future studies evaluate the effects of the length of captivity on post-release survival to produce additional guidelines for release. Information on the potential for full recovery and the length of the captive period required for achieving this rehabilitation will provide professionals with tools necessary for deciding whether to rehabilitate or euthanize individual animals.

Does human proximity affect antibody prevalence in marine-foraging river otters (Lontra canadensis)?

The investigation of diseases of free-ranging river otters (Lontra canadensis) is a primary conservation priority for this species; however, very little is known about diseases of river otters that forage in marine environments. To identify and better understand pathogens that could be important to marine-foraging river otters, other wildlife species, domestic animals, and humans and to determine if proximity to human population could be a factor in disease exposure, serum samples from 55 free-ranging marine-foraging river otters were tested for antibodies to selected pathogens. Thirty-five animals were captured in Prince William Sound, Alaska (USA), an area of low human density, and 20 were captured in the San Juan Islands, Washington State (USA), an area characterized by higher human density. Of 40 river otters tested by indirect immunofluorescent antibody test, 17.5% were seropositive (titer ≥320) for Toxoplasma gondii. All positive animals came from Washington. Of 35 river otters tested for antibodies to Leptospira interrogans using the microscopic agglutination test, 10 of 20 (50%) from Washington were seropositive (titer ≥200). None of the 15 tested animals from Alaska were positive. Antibodies to Neospora caninum (n=40), Sarcocystis neurona (n=40), Brucella abortus (n=55), avian influenza (n=40), canine distemper virus (n=55), phocine distemper virus (n=55), dolphin morbillivirus (n=55), porpoise morbillivirus (n=55), and Aleutian disease parvovirus (n=46) were not detected. Identifying exposure to T. gondii and L. interrogans in otters from Washington State but not in otters from Alaska suggests that living proximal to higher human density and its associated agricultural activities, domestic animals, and rodent populations could enhance river otter exposure to these pathogens.

Late Seasonal Breeding of River Otters in Yellowstone National Park

Abstract Seasonal breeding schedules for wild mammals, such as North American river otters (Lontra canadensis), often vary across their range. Previous studies in temperate regions found that river otters typically breed in March and April. Here we report on breeding condition and copulation of otters in June from Yellowstone Lake in Yellowstone National Park. Our findings suggest Yellowstone Lake otters have a relatively long breeding season, extending into June, or their breeding schedule is delayed so that energetically-demanding lactation coincides with spawning runs of Yellowstone cutthroat trout (Oncorhynchus clarki bouvieri).

Serologic Surveillance of Pathogens in a Declining Harbor Seal (Phoca vitulina) Population in Glacier Bay National Park, Alaska, USA and a Reference Site

The harbor seal population in Glacier Bay National Park, Alaska, has declined by over 70% since 1992. The reasons for this decline are not known. We examined serum antibodies and feces for evidence of exposure to multiple pathogens in this population. We also studied harbor seals from a reference site on Kodiak Island. In 2007, we found antibodies against Leptospira spp. in 31% of specimens from harbor seals in Glacier Bay, but no detectable serum antibodies in samples from Kodiak. In 2008, no samples had detectable antibodies against Leptospira spp. No serum antibodies against Toxoplasma gondii, morbilliviruses, or presence of Cryptosporidium in fecal samples were detected. However, Giardia was found in 6% of the fecal samples from Glacier Bay. Our results indicate that the harbor seal population in Glacier Bay National Park could be immunologically naïve to distemper viruses and therefore vulnerable to these pathogens. Given the relatively low prevalence of antibodies and low titers, pathogens likely are not the reason for the harbor seal decline in Glacier Bay.

Profiles of Fecal Porphyrins in River Otters Following the Exxon Valdez Oil Spill

Abstract Median levels of Coproporphyrin III (Copro III) in fecal samples of river otters ( Lontra canadensis ) collected from an oiled area in Prince William Sound, Alaska, USA, during 1990 were significantly higher than in samples collected from the same oiled area during 1996 ( p =0.011, one way analysis of variance), a nonoiled reference area in Prince William Sound during 1996 ( p =0.002) and a reference area in southeast Alaska during 1998 ( p =0.004). An overall test of significance that combined probabilities from the statistical analysis of this porphyrin study with those from other biomarker studies revealed a significant difference in physiological response of river otters between oiled and nonoiled areas of the Sound for 1990 ( p

An analysis of the fur of river otters in Prince William Sound, Alaska: oil related hydrocarbons 8 years after the Exxon Valdez oil spill

Abstract Approximately 8 years after the Exxon Valdez oil spill, river otters (Lutra canadensis) were trapped from the shoreline in both oiled (Knight Island) and nonoiled (Jackpot Bay) areas of Prince William Sound, Alaska. Captive river otters were wiped with isopropanol-soaked gauze and the gauze extracts were analyzed by gas chromatography with mass spectrometry detection. Differences in pentacosane (C-25) levels in the fur were observed between the oiled and nonoiled sites, while lower molecular weight aliphatics and aromatics were absent. These data are useful when evaluating the role of fur grooming in the long-term exposure of river otters to hydrocarbons and the expression of P450-1A in Knight Island otters.