a b s t r a c tDespite the ubiquity of denning as a natural history strategy among terrestrial vertebrates, little is known regarding basic patterns of within-den behavior, how such patterns are influenced by demographic and environmental parameters, or how within-den behavioral repertoires relate to activities performed in external environments. Den usage is believed to facilitate increased expression of behaviors that compromise fitness in external environments, though empirical data validating these assumptions are generally lacking. Relative isolation from external light cues within dens has been linked to temporal patterns of den use, yet few studies examine associations between photoperiod and rhythmicity strictly for within-den behavior. Also, for denning species with relatively equivalent parental investment, conclusions regarding sex-specific behavior have been equivocal, and no studies have examined potential segregation of parental activity within dens. We videorecorded 1506 h of within-den activity from 23 beaver (Castor canadensis) colonies and characterized behavioral patterns based on sex and age over daily and monthly intervals. Within-den time-activity budgets were equivalent among male and female adult beavers, with feeding, sleeping, allogrooming, and individual grooming accounting for more than 95% of all recorded behaviors. Behavioral repertoires within dens exhibited distinct seasonality and were influenced by temporal variation in external conditions associated with food availability, indicating linkages between activities within and outside of dens. Lastly, beaver age classes varied considerably in their associations between diel activity patterns and photoperiod, with adults and kits exhibiting single and multiple sleep-wake cycles, respectively.

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Ecosystem engineers are frequently observed to increase local biodiversity through their effects on resource flows. While promotion of successional processes and increased biodiversity may occur without direct interaction between ecosystem engineers and sympatric species, many cases exist where interactions are common. Under such conditions, it is unclear whether direct interactions serve to facilitate or inhibit coexistence of ecosystem engineers and the species attempting to use engineered habitats. We used remote videography within lodges of an ecosystem engineer, beavers (Castor canadensis), to quantify the taxonomic diversity of lodge use by non-beaver fauna and to characterize interactions between beavers and a second engineering species that commonly uses beaver-manipulated habitats, muskrats (Ondatra zibethicus). Beaver lodges were used by eleven types of vertebrates and invertebrates. Although no increased aggression was displayed by resident beavers towards intruding muskrats, the temporally partitioned patterns of muskrats’ and beavers’ entrances and exits to and from lodges, respectively, and altered behavior among both species during cohabitation, indicates that lodge use by muskrats represents an exploitative behavior as opposed to a mutualistic or even commensalistic relationship. We hypothesize that the ecological similarities between these species promotes competitive interactions, and the observed relationship highlights the tradeoffs faced by ecosystem engineers wherein constructed objects intended to exclude competitors are simultaneously associated with habitat modifications that promote the persistence of those same competitors.

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Theoretical treatments of intraguild predation and its effects on behavioral interactions regard the phenomenon as a size‐structured binary response wherein predation among competitors is completely successful or completely unsuccessful. However, intermediate outcomes occur when individuals escape intraguild (IG) interactions with non‐lethal injuries. While the effects of wounds for prey include compromised mobility and increased predation risk, the consequences of similar injuries among top predators are not well understood, despite the implications for species interactions. Using an amphibian IG predator, Ambystoma opacum (Caudata: Ambystomatidae), we examined associations between non‐lethal injuries and predator body size, foraging strategy, microhabitat selection, and intraspecific agonistic interactions. Wounds were common among IG predators, generally increasing in frequency throughout larval ontogeny. Non‐lethal injuries were associated with differences in predator body size and behavior, with injured predators exhibiting smaller body sizes, increased use of benthic microhabitats, reduced agonistic displays, and increased risk of intraspecific aggression. While such effects were not ultimately associated with reduced foraging success, non‐lethal injury could contribute to niche partitioning between injured and healthy predators via habitat selection, but injured predators likely continue to exert predatory pressure on IG and basal prey populations. Our results indicate that studies of top‐down population regulation should incorporate injury‐related modifications to both prey and predator behavior and size structure.

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Kin selection in larval amphibians is hypothesized to increase survival to metamorphosis. While kin selection may benefit amphibians with obligate metamorphosis, increased survival within sibships may exert fitness costs on facultatively paedomorphic species, such as increased competition among kin. Consequently, it is unclear whether such species should engage in kin selection. We investigated kin selection in a facultatively paedomorphic salamander, Ambystoma talpoideum, using laboratory behavioural trials and microcosm experiments. Individuals were most aggressive towards familiar siblings, and full-sibship groups incurred more injuries than mixed-sibship groups; however, familiar siblings ultimately exhibited higher survival. Thus, while short-term responses appeared to reflect the hypothesized costs of kin recognition, long-term patterns of survival did not support this hypothesis. The inconsistencies between results suggest that short-term studies may not capture ontogenetic variation in kin selection, and that long-term studies are needed to better test the hypothesized effects of kin selection on survival and metamorphosis.