Uncertainty during migration: selecting predictable resources in unpredictable conditions

• Authors:
  • Emilie Dedeban
  • Quinn M.R. Webber
  • Michel Laforge
  • Alec L. Robitaille
  • Eric Vander Wal

This repository contains the code accompanying the paper “Uncertainty on migration: selecting predictable resources in unpredictable conditions”. R scripts are under scripts/, Earth Engine scripts under EE/ and reused R functions are in R/.

Abstract

Environmental and climatic variation drive animal migration. Animals must adjust their behavioural strategies, e.g., habitat selection, to match best the variation in resources; resources whose value likely varies with conditions, such as weather. For example, climate change makes processes, such as snowmelt and the emergence of vegetation less predictable at the scale of months or weeks. Whereas climate change makes meteorological conditions unpredictable – or dynamic – at the scale of days and hours. The profitability of selecting any particular resource may vary by the local meteorological condition. We studied the impact of dynamic weather conditions on fine scale movements strategies and resource selection during spring migration of adult female woodland caribou (Rangifer tarandus). We assessed the role played by static resources such as open, lichen, and closed forest and their role in a context- dependent of dynamic weather conditions, including temperature, precipitation, and changing snow, i.e., snow water equivalent. We tested the role of static resources and dynamic conditions in three contexts: (1) whether caribou were encamped or moving behavioural using hidden Markov models; state-specific habitat selection for, and the interaction between, resources and conditions while (2) encamped and (3) moving. Weather conditions influenced the probability of moving or staying encamped, and the probability of selecting for a resource, which likely reflects the profitability of a given resource in a particular condition. The probability of staying encamped in the forest increases as the temperature increases. But also, the probability of selecting an open area is higher when precipitation is lower. We highlight how meteorological conditions modify the selection of a resource and likely the profitability of a given resource. The resource utility to a consumer is increasingly susceptible to climate- change induced effects.