All ungulates migrate- right? Identifying spatiotemporal migration patterns in an increasingly heterogeneous and asynchronous landscapes
Prevalent theories suggests that changing environmental conditions in conjunction with changes in predation have shifted the balance between these factors such that non-migratory residency is favored over a seasonal migratory life history. The state of Idaho contains a rich diversity of ungulates species occurring across a diverse landscape including high elevation deserts to temperate rain forests. However, climate trends of drier summers with warmer winters have also fostered an increase in fire disturbance and stand replacing bark beetle infestations which act synergistically to increase the disturbance frequency and severity at regional scales. The combination of having a diverse ungulate assemblage, across a variety of ecological zones, with regional shifts in disturbance regimes, offers the opportunity to understand how these factors influence ungulate migration as well as estimate the longevity of migratory life histories. To do so, we evaluate a suite of ungulate species, Elk (Cervus elaphus), mule deer (Odocoileus hemionus), moose (Alces americanus), Rocky Mountain bighorn sheep (Ovis canadenisis), and pronghorn antelope (Antilocarpa americana)and characterize their propensity to seasonally migrate using location data garnered from deployed GPS collars and net-squared displacement metrics (NSD) that identify migratory patterns and timing. We then evaluate mortality rates across seasonal habitats (migratory) or home-ranges (non-migratory) to compare and estimate the cost of seasonal migration relative to stationary residency. Elk, moose, and pronghorn antelope were shown to have a disparity in population’s propensity to seasonally migrate. Where these differences occur we compare these populations relative to disturbance regimes (annual time series by LandSat information, TM, ETM+, & OLI), predation risk (composition and abundance), and vegetation phenology (seasonal time series using MODIS satellite information).
Understanding how and where ungulates migrate, the influence of mortality during migration, fluctuating predation influence, changing climatic conditions, disturbance regimes and the synergistic effects of these multiple factors is technologically challenging but offers the opportunity to evaluate predominant ecological theories as well as evaluate their utility in managing species at provincial management scales.