DOI: 10.5061/dryad.stqjq2c3g
title: Woodland Caribou demographic data and range boundaries

description: As global climate change progresses, wildlife management will benefit from
 knowledge of demographic responses to climatic variation, particularly for
 species already endangered by other stressors. In Canada, climate change
 is expected to increasingly impact populations of threatened woodland
 caribou (Rangifer tarandus caribou) and much focus has been placed on how
 a warming climate has potentially facilitated the northward expansion of
 apparent competitors and novel predators. Climate change, however, may
 also exert more direct effects on caribou populations that are not
 mediated by predation. These effects include meteorological changes that
 influence resource availability and energy expenditure. Research on other
 ungulates suggests that climatic variation may have minimal impact on
 low-density populations such as woodland caribou because per-capita
 resources may remain sufficient even in “bad” years. We evaluated this
 prediction using demographic data from 21 populations in western Canada
 that were monitored for various intervals between 1994 and 2015. We
 specifically assessed whether juvenile recruitment and adult female
 survival were correlated with annual variation in meteorological metrics
 and plant phenology. Against expectations, we found that both vital rates
 appeared to be influenced by annual climatic variation. Juvenile
 recruitment was primarily correlated with variation in phenological
 conditions in the year prior to birth. Adult female survival was more
 strongly correlated with meteorological conditions and declined during
 colder, more variable winters. These responses may be influenced by the
 life history of woodland caribou, which reside in low-productivity refugia
 where small climatic changes may result in changes to resources that are
 sufficient to elicit strong demographic effects. Across all models,
 explained variation in vital rates was low, suggesting that other factors
 had greater influence on caribou demography. Nonetheless, given the
 declining trajectories of many woodland caribou populations, our results
 highlight the increased relevance of recovery actions when adverse
 climatic conditions are likely to negatively affect caribou demography.
description: Demographic data from woodland caribou were provided by the
 governments of Alberta, British Columbia, and Northwest
 Territories. Calves: adult female ratios (CAF) were estimated from aerial
 surveys conducted in March. These surveys recorded the total number of
 calves and adult females observed (mean = 147.3 adult females
 observed/caribou range/year [range: 11–1288]). CAF ratios were not
 adjusted to reflect the number of female calves to the total number of
 females across all age classes. Annual estimates of adult female survival
 (AVS) were derived from data collected from VHF- or GPS-collared adult
 females (≥2 years old; exact ages on capture are unknown) in each caribou
 population . For VHF-collared females, survival status was determined by
 aerial telemetry flights conducted 4–12 times per year, a monitoring
 frequency found to produce unbiased survival estimates.  Annual rates of
 AFS for each population were estimated using the Kaplan-Meier method in a
 staggered entry design. Also provided is a shapefile
 depicting the range boundaries for the 21 subpopulations of woodland
 caribou used in the analyses. The data were also provided by the
 governments of Alberta, British Columbia, and Northwest
 Territories.