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Woodland caribou is a Threatened or Endangered subspecies across much of Canada. In many cases, these caribou are declining because of human‐mediated predation in the form of apparent competition. Provincial and federal agencies have employed a number of conservation actions to arrest the decline, but insufficient time and limited replication make it difficult to test the efficacy of those activities. We built a three‐species population model that served as a tool to integrate current knowledge, explore uncertainties, and assess activities focused on the recovery of caribou. We applied the model to interconnected populations of caribou, moose, and wolves at two locations in Canada (Chinchaga [British Columbia], Charlevoix [Québec]) and explored the efficacy of conservation actions unique to each population: predator control, restoration of linear features, reduction of habitat for moose, supplementation, maternal pens, and predator exclosures. Results confirmed that caribou at these two locations faced different recovery challenges, dictated by specific population dynamics and threats. Wolf predation, enhanced by seismic lines and resource roads, was responsible for the decline of the simulated Chinchaga population. The most cost‐effective recovery actions for that population were long‐term lethal wolf control (λ1–50 = 1.014, $25,665/caribou), a large‐scale predator exclosure (λ1–50 = 1.015, $170,767/caribou), and the aggressive restoration of linear features (λ1–50 = 1.002, $531,675/caribou). In contrast, simulations suggested that calf predation by black bears, a fixed source of mortality in the model, limited the growth of the Charlevoix population. Assuming high survival of adult caribou and poor recruitment of juveniles, a maternal pen was the most effective action for the recovery of those caribou (λ1–50 = 1.004, $148,473/caribou). Short‐term population supplementation provided only a temporary increase in abundance (λ1–50 = 0.994, $62,143/caribou). The model was limited by ecological and data uncertainties, but served as an effective platform for representing and testing our understanding of the complex interspecific interactions that underlie the recovery of woodland caribou. [ABSTRACT FROM AUTHOR]

For many organisms, climate change can directly drive population declines, but it is less clear how such variation may influence populations indirectly through modified biotic interactions. For instance, how will climate change alter complex, multi-species relationships that are modulated by climatic variation and that underlie ecosystem-level processes? Caribou (Rangifer tarandus), a keystone species in Newfoundland, Canada, provides a useful model for unravelling potential and complex long-term implications of climate change on biotic interactions and population change. We measured cause-specific caribou calf predation (1990-2013) in Newfoundland relative to seasonal weather patterns. We show that black bear (Ursus americanus) predation is facilitated by time-lagged higher summer growing degree days, whereas coyote (Canis latrans) predation increases with current precipitation and winter temperature. Based on future climate forecasts for the region, we illustrate that, through time, coyote predation on caribou calves could become increasingly important, whereas the influence of black bear would remain unchanged. From these predictions, demographic projections for caribou suggest long-term population limitation specifically through indirect effects of climate change on calf predation rates by coyotes. While our work assumes limited impact of climate change on other processes, it illustrates the range of impact that climate change can have on predator-prey interactions. We conclude that future efforts to predict potential effects of climate change on populations and ecosystems should include assessment of both direct and indirect effects, including climate-predator interactions.

Predator species identification is an important step in understanding predator-prey interactions, but predator identifications using kill site observations are often unreliable. We used molecular tools to analyse predator saliva, scat and hair from caribou calf kills in Newfoundland, Canada to identify the predator species, individual and sex. We sampled DNA from 32 carcasses using cotton swabs to collect predator saliva. We used fragment length analysis and sequencing of mitochondrial DNA to distinguish between coyote, black bear, Canada lynx and red fox and used nuclear DNA microsatellite analysis to identify individuals. We compared predator species detected using molecular tools to those assigned via field observations at each kill. We identified a predator species at 94% of carcasses using molecular methods, while observational methods assigned a predator species to 62.5% of kills. Molecular methods attributed 66.7% of kills to coyote and 33.3% to black bear, while observations assigned 40%, 45%, 10% and 5% to coyote, bear, lynx and fox, respectively. Individual identification was successful at 70% of kills where a predator species was identified. Only one individual was identified at each kill, but some individuals were found at multiple kills. Predator sex was predominantly male. We demonstrate the first large-scale evaluation of predator species, individual and sex identification using molecular techniques to extract DNA from swabs of wild prey carcasses. Our results indicate that kill site swabs (i) can be highly successful in identifying the predator species and individual responsible; and (ii) serve to inform and complement traditional methods., (© 2013 John Wiley & Sons Ltd.)