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Boreal ecosystems are experiencing extensive changes because of anthropogenic stressors such as climate change. Information on density of species at multiple sites is vital to understand and manage the impact of these changing conditions on boreal forest communities. Yet, for most boreal forest species, including the vast majority of mammals, obtaining reliable estimates of density is exceedingly difficult. Recently developed methods for the estimation of densities of unmarked animals from camera-trapping data could help to overcome this hurdle, but have not yet been empirically validated in many ecosystems. Here, we assess the ability of camera traps to estimate density of snowshoe hare (Lepus americanus) using three different models: the random encounter model (REM), the random encounter and staying time (REST) model, and the time-to-event (TTE) model. We additionally evaluate the relationship between hare density and two simple indices based on camera detection rate and pellet counts. Across 13 sites in North Central Washington, United States, we compared live-trapping spatially explicit capture–recapture (SECR) estimates of density to the three camera-based density models and the two indices. We found that the camera-based models, in particular the REM and REST models, performed well in estimating densities consistent with the live-trapping data, with an average difference in density from SECR-based estimates of only 0.12 and 0.13 hares/ha, respectively. Both indices also had strong predictive relationships with hare density. Our results show that, owing to their noninvasive nature and relative ease of application, camera-based methods could be used to obtain hare density estimates at much larger spatiotemporal scales than have been applied to date. Given the keystone role of hare in boreal ecosystems, and emerging evidence of hare range retraction, the ability to estimate densities across many sites is a key tool for hare conservation and management. Moreover, our results are highly encouraging for the application of camera-based methods to obtain density estimates on a wide variety of boreal forest species, though additional validation will be necessary.

Congeneric species often share ecological niche space resulting in competitive interactions that either limit co-occurrence or lead to niche partitioning. Differences in fundamental nutritional niches mediated through character displacement or isolation during evolution are potential mechanisms that could explain overlapping distribution patterns of congenerics. We directly compared nutritional requirements and tolerances that influence the fundamental niche of mule (Odocoileus hemionus) and white-tailed deer (O. virginianus), which occur in allopatry and sympatry in similar realized ecological niches across their ranges in North America. Digestible energy and protein requirements and tolerances for plant fiber and plant secondary metabolites (PSMs) of both deer species were quantified using in vivo digestion and intake tolerance trials with six diets ranging in content of fiber, protein, and PSMs using tractable deer raised under identical conditions in captivity. We found that compared with white-tailed deer, mule deer required 54% less digestible protein and 21% less digestible energy intake per day to maintain body mass and nitrogen balance. In addition, they had higher fiber, energy, and dry matter digestibility and produced glucuronic acid (a byproduct of PSM detoxification) at a slower rate when consuming the monoterpene α-pinene. The mule deers’ enhanced physiological abilities to cope with low-quality, chemically defended forages relative to white-tailed deer might minimize potential competitive interactions in shared landscapes and provide a modest advantage to mule deer in habitats dominated by low-quality forages.

The persistence of cold-adapted species along their equatorial range edge (i.e., southern range edge for species in the Northern Hemisphere and northern range edge for species in the Southern Hemisphere) is threatened by climate change. These species will be challenged not just by unfavorable climatic regimes, but also by changing biotic interactions, which may be more intense along equatorial edges. However, we currently have a poor understanding of the nature of biotic interactions at range edges and how climate may mediate those interactions, particularly for cold-adapted mammals. We studied the distribution of threatened Canada lynx (Lynx canadensis) at their southern range edge in northern Washington, United States from 2014 to 2016. Using data collected from 397 camera-trap stations in snow-on and snow-off seasons, and single- and 2-species occupancy models, we investigated seasonal patterns of habitat selection and spatial association of lynx with their primary prey (snowshoe hares, Lepus americanus) and potential competitors (bobcats, Lynx rufus; cougars, Puma concolor). Single-species occupancy models revealed lynx distribution was strongly associated with snowshoe hare abundance and topographic variables related to lower temperatures and increased moisture. In contrast, bobcats and cougars were more generalized in their habitat associations or displayed the reverse response to environmental variables. Spatial overlap of the 3 felid species increased during snow-off seasons. Two-species occupancy models showed a decrease in use of camera sites by lynx when bobcats were present, suggesting lynx were avoiding their warm-adapted competitor. Taken together, these results suggest that biotic interactions are partly shaping large-scale lynx distribution patterns along their southern range edge. Increasing temperatures and loss of snow may result in a combination of habitat isolation and potential for increased competitive interactions for lynx at the margins of their range.

The coyote (Canis latrans) has recently expanded its geographic range into Florida, and the impacts of this range expansion on Florida ecosystems are likely to be complex. An area of particular concern is the effect on native carnivores. From May 2001 to May 2002, we investigated the ecological relationships between the coyote and bobcat (Lynx rufus) in south-central Florida to determine how they partition space, habitat, time, and food. Ecological separation was facilitated by dietary differences. Coyotes preyed primarily upon large ungulates and consumed substantial quantities of fruit, whereas bobcats primarily consumed rodents and lagomorphs. Coyotes and bobcats displayed similar habitat selection and activity patterns, and their high interspecific overlap in home ranges indicated a lack of large-scale spatial segregation. However, at the finer scale of core areas, patterns of spatial segregation were present. The lack of evidence for negative interactions at our study site suggests that non-overlapping core areas reduces agonistic encounters between the 2 species.

Olfactory communication among mammals remains poorly studied yet may be key to understanding their ecology. This is particularly true for mammalian carnivores, which rely extensively on scent marking for communication. Previous research suggests that carnivore latrines play a large role in both intra- and interspecific communication. Despite the apparent complexity of mammal use of latrines, little work has examined behavior patterns of species that visit latrines. We used motion-triggered video cameras to study use and behavior of mammals at ocelot ( Leopardus pardalis ) latrines in Costa Rica. We documented temporal patterns of use by the focal species (ocelots), diversity of mammalian species using latrines, and behaviors that occurred at these sites. Ocelots showed peaks in visitation every 60–67 days and a shorter gap between intersexual versus intrasexual visits, supporting the idea that ocelot latrines are used to communicate information about reproductive status. Fourteen terrestrial mammal species visited the latrines, and these species engaged in a variety of behaviors, including mark investigation, scent marking, and acceptance of scent marks. The complexity and frequency of behaviors by nonfocal species suggest that latrines may play as important a role in communication for these other species as they do for ocelots. La comunicacion olfativa entre mamiferos ha sido poco estudiada, sin embargo puede ser la clave para el entendimiento de su ecologia. Esto es particularmente cierto para mamiferos carnivoros quienes dependen extensivamente de el marcaje de rastros olfativos para su comunicacion. Estudios previos siguieren que las letrinas juegan un rol importante en la comunicacion intra- e inter-especifica. A pesar de la aparente complejidad del uso de letrinas por parte de mamiferos, pocos trabajos han examinado los patrones de comportamiento de las especies que las visitan. Utilizamos camaras de videos sensibles al movimiento para estudiar el uso y comportamiento de mamiferos en letrinas de ocelotes ( Leopardus pardalis ) en Costa Rica. Documentamos los patrones de uso temporal por parte de especies focales (ocelotes), la diversidad de especies de mamiferos y los comportamientos que ocurrieron en estos lugares. Los resultados indican que el uso por parte de los ocelotes muestran picos de visitas cada 60 a 67 dias y un intervalo mas corto para visitas inter-sexuales que para visitas intra-sexuales. Esto apoya la idea de que las letrinas de los ocelotes son utilizadas para comunicar estatus reproductivos. Un total de catorce mamiferos terrestres visitaron las letrinas y estas especies mostraron una variedad de comportamientos, incluyendo investigacion, marcaje y aceptacion de rastros olfativos. La complejidad y frecuencia de comportamientos por especies no focales, sugieren que las letrinas pueden jugar un rol importante en la comunicacion de otras especies como lo es para los ocelotes.