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Wood bison migration metrics and environmental covariates

Hecker, Lee1; Nielsen, Scott2; Edwards, Mark3

Published Nov 19, 2024 on Dryad. https://doi.org/10.5061/dryad.hdr7sqvt4

Data files

Nov 19, 2024 version files 108.39 MB

Abstract

Migration is an evolutionarily stable adaptation when movement costs are outweighed by fitness gains. Migration is defined as the predictable movement between seasonal ranges in response to differential resource availability. However, migrations to locate suitable mates, and calving or nursery grounds are also common across taxa. For ungulates, the growth of new vegetation (i.e., green-wave) has been identified as a key mechanism influencing migration between seasonal ranges. We investigated how the green-wave influenced migration in a wood bison (Bison bison athabascae) population in northern Alberta, Canada, while also considering risk of calf predation by wolves (Canis lupus). Each year, all collared females in the population migrated an average of 28-kilometers over 6-days to a region at the western edge of their annual range between late-May and early-June. By late-June they migrated back to their core range, averaging a 40-kilometer migration distance over 10-days. We found that the green-wave influenced both the timing of migration and selection of habitats during migration. Risk of predation was not found to influence habitat selection during migration. However, the herd congregating and leaving their spring range as a group suggests risk of predation may be an evolutionary mechanism contributing to this migratory behavior. The timing of migration and congregation aligns with the expected timing of parturition giving further support that both the green-wave and predation risk influence migration. We provide a framework to assess interrelated mechanisms influencing migration, which is important to those studying, managing, and/or conserving migratory ungulates.