Variation in winter site fidelity within and among individuals influences movement behavior in a partially migratory ungulate

PLoS One. 2021 Sep 30;16(9):e0258128. doi: 10.1371/journal.pone.0258128. eCollection 2021.

Abstract

Many animals migrate to take advantage of temporal and spatial variability in resources. These benefits are offset with costs like increased energetic expenditure and travel through unfamiliar areas. Differences in the cost-benefit ratio for individuals may lead to partial migration with one portion of a population migrating while another does not. We investigated migration dynamics and winter site fidelity for a long-distance partial migrant, barren ground caribou (Rangifer tarandus granti) of the Teshekpuk Caribou Herd in northern Alaska. We used GPS telemetry for 76 female caribou over 164 annual movement trajectories to identify timing and location of migration and winter use, proportion of migrants, and fidelity to different herd wintering areas. We found within-individual variation in movement behavior and wintering area use by the Teshekpuk Caribou Herd, adding caribou to the growing list of ungulates that can exhibit migratory plasticity. Using a first passage time-net squared displacement approach, we classified 78.7% of annual movement paths as migration, 11.6% as residency, and 9.8% as another strategy. Timing and distance of migration varied by season and wintering area. Duration of migration was longer for fall migration than for spring, which may relate to the latter featuring more directed movement. Caribou utilized four wintering areas, with multiple areas used each year. This variation occurred not just among different individuals, but state sequence analyses indicated low fidelity of individuals to wintering areas among years. Variability in movement behavior can have fitness consequences. As caribou face the pressures of a rapidly warming Arctic and ongoing human development and activities, further research is needed to investigate what factors influence this diversity of behaviors in Alaska and across the circumpolar Arctic.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alaska
  • Animal Migration / physiology*
  • Animals
  • Ecosystem
  • Female
  • Movement
  • Reindeer*
  • Seasons*
  • Telemetry

Grants and funding

Support for the North Slope Borough Department of Wildlife Management collaring efforts was made possible through grants from the Alaska Department of Commerce, Community and Economic Development and the United States Bureau of Land Management. Support for TJF was provided by grants from the Wilburforce Foundation. AKP is employed by the commercial consulting company ABR, Inc. – Environmental Research & Services, which provided salary support. ConocoPhillips Alaska, Inc. also provided some funding for AKP. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific roles of each author are articulated in the ‘Author Contributions’ section.