Individuals of 1 species might obtain information by eavesdropping on calls produced by a syntopic species. Intercepting alarm calls allows the eavesdropper to respond with antipredator behavior without the need to produce its own call, which might attract the attention of a predator. We examined eavesdropping on heterospecific alarm calls by nonsocial eastern chipmunks (Tamias striatus) and woodchucks (Marmota monax), which live in the same community, share some predators, are solitary, and produce distinct alarm calls. If these 2 species recognize heterospecific alarm calls, we should see antipredator behaviors similar to those displayed upon hearing a conspecific's alarm call. We broadcast single alarm calls of woodchucks, eastern chipmunks, and American crows (Corvus brachyrhynchos) to individuals of the first 2 species, using the territorial song of the syntopic male black-capped chickadee (Poecile atricapillus) as a control. Woodchucks became more vigilant after hearing both conspecific and heterospecific alarm calls compared with controls; however, they spent more time vigilant in response to conspecific alarm calls compared to heterospecific alarm calls. Thus, woodchucks apparently can recognize heterospecific alarm calls, but they appear to process conspecific and heterospecific calls differently. Eastern chipmunks responded to heterospecific alarm calls, but sample sizes were small and the results not definitive. Our results suggest that nonsocial mammals might benefit from eavesdropping on heterospecifics.

Demographic structure is central to understanding the dynamics of animal populations. However, determining the age of free-ranging mammals is difficult, and currently impossible when sampling with noninvasive, genetic-based approaches. We present a method to estimate age class by combining measures of telomere lengths with other biologically meaningful covariates in a Bayesian network. We applied this approach to American and Pacific martens (Martes americana and M. caurina) and compared predicted age with that obtained from counts of cementum annuli. Using telomere length and the covariates sex, species, and estimates of population density obtained from commercial trapping records, we assigned martens to juvenile (<1 year) or adult (≥1 year) classes with 75–88% accuracy. In our analysis for live-captured martens, for which information on body size and whether animals were juveniles or adults would be available, we achieved 90–93% accuracy when assigning individuals to 5 discrete age classes (0–4 years). This general approach could be extended to other species for noninvasive estimation of age class, or in place of invasive aging methods, and enable demographically based population analyses that have heretofore been impossible.

Winter breeding under the snow is a critical ecological adaptation of lemmings and a key demographic process in their periodic multiannual fluctuations in abundance. However, logistic constraints limit our ability to quantify lemming winter reproduction. We evaluated a method to infer lemming reproduction based on the size distribution of feces found in their winter nests. We determined criteria allowing identification of reproduction from feces found in nests, using golden Syrian hamsters (Mesocricetus auratus) as a surrogate model. We found a large difference in individual mass of feces between juveniles at weaning and adults. Using bimodal distribution of feces size, mean size difference, and proportion of small feces, we showed that visual inspection of ≥30 feces was sufficient to infer hamster reproduction with an accuracy of >95%. We also applied the method to winter nests of collared lemmings (Dicrostonyx groenlandicus) and brown lemmings (Lemmus trimucronatus) found in the Canadian Arctic. Because characteristics of feces found in lemming winter nests matched those found in hamster nests, we suggest that the method can be used to detect winter reproductive activity of lemmings.

Demographic rates of animals (i.e., survival and breeding success) generally increase with experience early in life, but temporal variation in the effect of experience on demography is not well understood. The demographic difference between inexperienced versus experienced breeders can be accentuated during poor environmental conditions when food is scarce, or the difference can remain constant regardless of environmental fluctuation. I tested the hypothesis that environmental variation accentuates the difference between inexperienced and experienced breeders using 20 years of capture–mark–recapture data for northern elephant seals (Mirounga angustirostris) from the Farallon Islands, California. I estimated year-specific survival probabilities, breeding propensity (the probability that an individual will breed in year x), and breeding success of primiparous (inexperienced) and multiparous (experienced) females. Primiparous breeders did not suffer more than experienced breeders during years of environmental stress. The selection hypothesis (a decrease in heterogeneity in individual quality within cohorts over time, based on selection pressure) could explain the experience-related improvement in survival and breeding success. Lower variances in survival of multiparous breeders suggest that primiparous adults constitute a more heterogeneous portion of the population, and the 1st breeding event might act as a selective process leading to a more homogeneous pool of multiparous breeders.

Breeding success among male white-tailed deer (Odocoileus virginianus) has been correlated with numerous physical and physiological variables. We investigated the effect of relative body mass on breeding success in captive male deer from 21 breeding trials. Contrary to our prediction, larger males on average had identical levels of breeding success (59% of breeding opportunities) in the 1st and 2nd halves of the breeding season. The variability of breeding success increased with greater relative mass; thus deer with substantial mass disadvantages had only limited success, and males weighing ≥92% of the pen average had success ranging from 0% to 100% of potential breeding opportunities. Although constant proximity limited males primarily to a strategy of direct confrontation, some subordinate males evidently mated opportunistically when >1 female was receptive. We conclude that ≥1 uncontrolled variable, possibly related to aggressiveness or life-history strategy, remained influential and limited the ability of some males to compete successfully in spite of greater relative body mass.

A trade-off exists for migrating animals as to whether to migrate or remain residents. Few studies have documented relationships between landscape variables and deer migration strategies. From 2000 to 2007 we captured 267 adult female white-tailed deer (Odocoileus virginianus) at 7 study sites in Minnesota and South Dakota and monitored 149 individuals through ≥3 seasonal migration periods (585 deer-migration seasons). All deer classified as obligate migrators with ≥3 migrations (range 3–9 migration seasons) maintained their obligate status for the duration of the study. Multinomial logistic odds ratios from generalized estimating equations indicated that the odds of being a resident increased by 1.4 and 1.3 per 1-unit increase in forest patch density and mean area, respectively, compared to migrating deer. Odds of being an obligate migrator increased by 0.7 and 0.8 per 1-unit decrease in forest patch density and mean area, respectively, compared to resident or conditional migrating deer. Areas inhabited by resident deer were characterized by greater number of forest patches per 100 ha and larger mean forest patch area than conditional and obligate migrant areas. Odds of migrating increased by 1.1 per 1-unit increase in deer winter severity index. Migration behavior of white-tailed deer varied among regions, and land-cover and landscape characteristics provided predictive indicators of migration strategies for deer that could have important implications for conservation, metapopulation dynamics, and species management.

We investigated the association patterns of 48 identifiable Commerson's dolphins (Cephalorhynchus commersonii) photographed 2 or more times over a 2-year period in Bahía Engaño, Chubut, Argentina. The associations among them were not different from random for short time periods (7 days) but were significantly different from random for longer periods. Lagged identification rate and lagged association rate models show that dolphins remained in the area on average 15 days and then moved away as the original groups dissolved. Commerson's dolphins appear to have a fission–fusion society, and the observed strength of their associations is in concordance with the predictions regarding their body size and ranging patterns. The dolphins seem to rely on Bahía Engaño as a core area for most of their activities, but the aggregations are labile and some individuals remain associated in a more stable manner with only a few other individuals.

The marsh rice rat (Oryzomys palustris) is a semiaquatic rodent occurring in wetland habitats throughout the southeastern United States and along the Atlantic Coast. A lack of understanding of its ecology and distribution in inland parts of its range limits our ability to assess the species' status and needs. We trapped rice rats at random and previously occupied, wetland-dominated sites in 5 southern Illinois watersheds during 2007–2009 to determine key variables affecting habitat occupancy by the species. We detected rice rats within 3 of 5 watersheds, 16 of 48 sites, and at 5 new locations. Most rice rats were captured in permanent or semipermanent emergent wetlands (n  =  89; 46.3% of total captures) or roadside ditches in wetland patches (n  =  73; 38.0%). Habitat associations determined using logistic regression and occupancy modeling provided similar results. Percent herbaceous cover and percent visual obstruction (0.0–0.5 m) were the most important microhabitat variables positively influencing rice rat occurrence. In areas surrounding wetlands, the proportion composed of upland grass was the best predictive variable of rice rat occurrence among landcover models. Estimates of daily detection probability were high (0.44–0.87). The likelihood of occupancy increased with the proportion of upland grass cover adjacent to wetland complex and percent herbaceous cover at the microhabitat scale. Inland metapopulations of rice rats are clustered throughout the southeastern United States in appropriate wetland complexes. Construction, restoration, and protection of emergent wetlands, and consideration of connectivity and adjacent grasslands, should benefit rice rat populations.

Habitat fragmentation often separates and reduces populations of vertebrates, but the