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 to a geographical feature that conforms to a relatively linear pattern. Consequently, conventional analysis techniques may overestimate home ranges. We used simulations based upon coastal river otters (Lontra canadensis), a species that primarily uses the aquatic-terrestrial interface, to evaluate the efficacy of fixed and adaptive kernel estimates with various smoothing parameters. Measures of shoreline length within contours from fixed kernel analyses and the reference smoothing parameter were best for estimates of 95% home ranges, because smoothing with least squares cross validation (LSCV) often resulted in inconsistent results, excessive fragmentation, and marked underestimates of linear home ranges. Core areas (50% density contours) were best defined with fixed kernel LSCV estimates. Fewer locations underestimated linear home ranges, and there was a subtle positive relation between home-range size and autocorrelation. Generally, as location numbers increased, autocorrelation increased, but differences from the ''true'' home range decreased. Results were similar for our simulations and empirical data from 13 river otters. Examination of empirical data revealed that data with high positive autocorrelation illustrated seasonal reproductive activities. Because autocorrelation does not negatively influence estimates of linear home ranges, assessment of independence between data points may be more appropriately viewed as a means to identify important behavioral information, rather than as a hindrance.

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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.

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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 organization in river otters resulted in different foraging strategies and scent-marking behaviors. Social otters were more closely associated with schooling fishes and used latrines for intra-group communication, whereas nonsocial otters, which concentrated on intertidal and subtidal fishes, probably signaled mutual avoidance. In contrast, females appeared to use latrines for the defense of territories. Social otters used fewer sites with greater intensity, whereas nonsocial otters used more sites with lower intensity. These different functions of scent-marking and associated behaviors of otters resulted in high variability in nutrient inputs to different latrine sites. Although some sites may receive 2.7 g N·m Ϫ2 ·yr Ϫ1 and 0.4 g P·m Ϫ2 ·yr Ϫ1 , others may be fertilized with up to 47.6 g N·m Ϫ2 ·yr Ϫ1 and 6.7 g P·m Ϫ2 ·yr Ϫ1 . This spatial variability and the temporal changes in resource sheds is likely to result in the creation of heterogeneous landscape at the land margin.