Year of Award

2025

Document Type

Dissertation

Degree Type

Doctor of Philosophy (PhD)

Degree Name

Fish and Wildlife Biology

Department or School/College

W.A. Franke College of Forestry and Conservation

Committee Chair

Mark Hebblewhite

Commitee Members

Evelyn Merrill, Jedediah Brodie, Paul M. Lukacs, Hugh Robinson

Keywords

Cervus canadensis, climate change, partial migration, phenological trap, trophic mismatch, wildlife management

Abstract

The survival and reproduction of large herbivores depend on the synchronization of life-history events with ephemeral resource availability. Migratory ungulates have navigated this seasonality by relying on environmental cues (e.g., snowmelt or green-up) to predict when to migrate to distant foraging areas. However, anthropogenic climate change is rapidly altering environmental baselines. This dissertation investigates the intersection of climate change, behavioral plasticity, and reproductive ecology in a partially migratory elk (Cervus canadensis) population in Alberta, Canada. Integrating 22 years of longitudinal monitoring data (2002–2024) of individual elk with remotely sensed NDVI and statistical modeling, I examine how three coexisting migratory tactics navigate a landscape where the phenological patterns of resource availability are changing. First, I synthesize how climate change alters herbivore nutrition, distinguishing between shifts in duration versus phenological timing of resources. I then estimate a multidecadal baseline of migratory behavior using models of net-squared displacement and a machine-learning approach to estimate parturition from GPS movement data. I find that while reproductive timing remains relatively stable, migratory behavior exhibits divergent trends between migratory tactics. Western migrants maintain a fixed schedule constrained by highelevation environments, while eastern migrants display plasticity, shifting their spring migration later over time. Finally, I identify the mechanism driving these trends, revealing a novel "phenological trap" driven by decoupling of local and distant forage resource cues. I demonstrate that the winter range (the cue) is phenologically delaying (+0.66 days/year), while the eastern summer range (the target) is advancing (-0.76 days/year). Eastern elk appear to rely on a delayed forage productivity threshold on the winter range to trigger spring migration. This reliance on a decoupling cue mechanistically forces them into a widening mismatch, from a state of "jumping" to "trailing" the green wave. Finally, I test the demographic consequences of this asynchrony. I detected a marginally significant decline in summer calf survival associated with phenological trophic mismatch. Although adult females appear buffered from direct nutritional costs, the burden of mismatch might be shifting to the next generation. Collectively, these findings challenge the assumption that behavioral plasticity acts as a universal buffer against climate change, demonstrating how plasticity can paradoxically accelerate mismatch in complex environments when environmental information becomes unreliable.

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© Copyright 2025 Tara Kelly Meyer