Demographic responses of a threatened, low-density ungulate to annual variation in meteorological and phenological conditions

PLoS One. 2021 Oct 8;16(10):e0258136. doi: 10.1371/journal.pone.0258136. eCollection 2021.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Animals, Wild / physiology
  • Canada
  • Climate Change
  • Conservation of Natural Resources*
  • Ecosystem*
  • Endangered Species
  • Mammals / physiology*
  • Meteorology
  • Models, Biological
  • Population Dynamics
  • Predatory Behavior
  • Reindeer / physiology*
  • Seasons

Associated data

  • Dryad/10.5061/dryad.stqjq2c3g

Grants and funding

Partial funding for this work was provided to CAD, SG and RS by the British Columbia Oil and Gas Research and Innovation Society (www.bcogris.ca). The funders did not play any role in the study design, data collection and analysis, decision to publish or preparation of the manuscript. In-kind contributions of caribou demographic data were provided by the governments of British Columbia, Alberta, and the Northwest Territories. None of these governments influenced the design, data analysis, manuscript preparation or the decision to publish.