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Bastille-Rousseau, Guillaume; Schaefer, James A.; Lewis, Keith P.; Mumma, Matthew; Ellington, E. Hance; Rayl, Nathaniel D.; Mahoney, Shane P.; Pouliot, Darren; Murray, Dennis L.; Mumma, Matthew A. — 2016-10-27 1. Climate can have direct and indirect effects on population dynamics via changes in resource competition or predation risk, but this influence can be modulated by density- or phase-dependent processes. We hypothesized that for ungulates, climatic conditions close to parturition have a greater influence on the predation risk of neonates during population declines, when females are already under nutritional stress triggered by food limitation. 2. We examined the presence of phase-dependent climate-predator interactions on neonatal ungulate survival by comparing spatial and temporal fluctuations in climatic conditions, cause specific mortality, and per capita resource limitation. We determined cause-specific fates of 1384 caribou (Rangifer tarandus) from 10 herds in Newfoundland, spanning more than 30 years during periods of numerical increase and decline, while exposed to predation from black bears (Ursus americanus) and coyotes (Canis latrans). 3. We conducted Cox proportional hazards analysis for competing risks, fit as a function of weather metrics, to assess pre- and post-partum climatic influences on survival on herds in population increase and decline phases. We used cumulative incidence functions to compare temporal changes in risk from predators. 4. Our results support our main hypothesis; when caribou populations increased, weather conditions preceding calving were the main determinants of cause-specific mortality, but when populations declined, weather conditions during calving also influenced predator-driven mortality. Cause-specific analysis showed that weather conditions can differentially affect predation risk between black bears and coyotes with specific variables increasing the risk from one species and decreasing the risk from the other. 5. For caribou, nutritional stress appears to increase predation risk on neonates, an interaction which is exacerbated by susceptibility to climatic events. These findings support the phase-dependent climate-predator (PDCP) interactions framework, where maternal body condition influences susceptibility to climate-related events and, subsequently, risk from predation.

Potts, Jonathan R.; Bastille-Rousseau, Guillaume; Murray, Dennis L.; Schaefer, James A.; Lewis, Mark A. — 2014-11-19 1. Predicting space use patterns of animals from their interactions with the environment is fundamental for understanding the effect of habitat changes on ecosystem functioning. Recent attempts to address this problem have sought to unify resource selection analysis, where animal space use is derived from available habitat quality, and mechanistic movement models, where detailed movement processes of an animal are used to predict its emergent utilisation distribution. Such models bias the animal's movement towards patches that are easily available and resource-rich, and the result is a predicted probability density at a given position being a function of the habitat quality at that position. However, in reality, the probability that an animal will use a patch of the terrain tends to be a function of the resource quality in both that patch and the surrounding habitat. 2. We propose a mechanistic model where this non-local effect of resources naturally emerges from the local movement processes, by taking into account the relative utility of both the habitat where the animal currently resides and that of where it is moving. We give statistical techniques to parametrize the model from location data, and demonstrate application of these techniques to GPS location data of caribou (Rangifer tarandus) in Newfoundland. 3. Steady-state animal probability distributions arising from the model have complex patterns that cannot be expressed simply as a function of the local quality of the habitat. In particular, large areas of good habitat are used more intensively than smaller patches of equal quality habitat, whereas isolated patches are used less frequently. Both of these are real aspects of animal space use missing from previous mechanistic resource-selection models. 4. Whilst we focus on habitats in this paper, our modelling framework can be readily used with any environmental covariates, and therefore represents a unification of mechanistic modelling and step-selection approaches to understanding animal space use.

Jenkins, Deborah A.; Lecomte, Nicolas; Schaefer, James A.; Olsen, Steffen M.; Swingedouw, Didier; Côté, Steeve D.; Pellissier, Loïc; Yannic, Glenn — 2016-08-24 Global warming threatens to reduce population connectivity for terrestrial wildlife through significant and rapid changes to sea ice. Using genetic fingerprinting, we contrasted extant connectivity in island-dwelling Peary caribou in northern Canada with continental-migratory caribou. We next examined if sea-ice contractions in the last decades modulated population connectivity and explored the possible impact of future climate change on long-term connectivity among island caribou. We found a strong correlation between genetic and geodesic distances for both continental and Peary caribou, even after accounting for the possible effect of sea surface. Sea ice has thus been an effective corridor for Peary caribou, promoting inter-island connectivity and population mixing. Using a time series of remote sensing sea-ice data, we show that landscape resistance in the Canadian Arctic Archipelago has increased by approximately 15% since 1979 and may further increase by 20–77% by 2086 under a high-emission scenario (RCP8.5). Under the persistent increase in greenhouse gas concentrations, reduced connectivity may isolate island-dwelling caribou with potentially significant consequences for population viability.