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Habitat loss on seasonal migratory range imperils an endangered ungulate

Citation

Williams, Sara et al. (2021), Habitat loss on seasonal migratory range imperils an endangered ungulate, Dryad, Dataset, https://doi.org/10.5061/dryad.cc2fqz652

Abstract

  1. Endangered species policies and their associated recovery documents and management actions do not always sufficiently address the importance of migratory behavior and seasonal ranges for imperiled populations.
  2. Using a telemetry location dataset spanning 1981 – 2018, we tested for changes in prevalence of migratory tactics (resident, migrant) over time, switching between tactics, shifts in seasonal space-use including migration corridors, and survival consequences of migrant and resident tactics for 237 adult female endangered woodland mountain caribou in one population in western Canada.
  3. Over more than three decades, the proportion of individuals displaying annual migration to the low elevation forested winter range declined from nearly 100% to 38%. Correspondingly, there was a strong switch away from being migrant to being year-round residents at high elevation.
  4. These behavioral changes corresponded to abandonment of low elevation winter ranges in association with increasing levels of anthropogenic land uses, including forestry and oil and gas developments.  Furthermore, there were no identifiable migration corridors to target for migratory route protection.
  5. These shifts translated to lower survival rates, particularly for caribou demonstrating resident tactics, consistent with recent declines of the caribou population. That migrants switched to residency in their largely undisturbed summer range, despite lower survival, indicates maladaptive habitat selection consistent with recent patterns of mountain caribou extirpations.
  6. Globally, endangered species policies and their associated recovery plans and management actions often do not explicitly consider the challenge of protecting migratory species. Effective conservation of migratory species requires protecting critical habitats needed for the entire life history of the species, including all seasonal ranges and migratory habitat.

Methods

1. "RRPC_migation_class.csv": migration tactic classification data for use in anlaysis of estimating probability of being migrant and probability of switching tactic

VHF or GPS radio collar locations used to classify migratory tactic using net-squared displacement (NSD) models in the ‘migrateR’ package in the program R (Bunnefeld et al., 2011; R Core Team, 2019; Spitz, Hebblewhite, & Stephenson, 2017) using a single location/day for individuals that had > 20 locations/year to ensure model convergence using NSD. Other individuals’ movement trajectories were not suitable for NSD models because of too few locations (e.g., VHF data) or lack of a complete annual cycle (e.g. mortalities, collar failures, etc.). To assess tactic for these latter individuals, we developed decision rules based on successfully NSD classified individuals who showed clear migration movements (Eggeman et al., 2016; see Supporting Information).

Decision rules for assigning migratory tactic:

First, we assumed all caribou spent summer (June – August) at high elevations because no monitored caribou summered in low elevation areas. Thus, the crucial test for migrant classification was whether we found even a single location of an individual in winter (Jan – March) in lower-elevation foothills.  Conversely, if all an individual’s locations during winter occurred in high-elevation range occupied during summer, we classified this individual to be a high-elevation resident.

In cases where migratory tactic could not be determined, it was assigned as unknown.

 

2. "RRPC_capture.csv": capture date information per individual for use in survival analysis

3. "RRPC_fate.csv": fate information per individual-year for use in survival analysis