Classifying the migration behaviors of pronghorn on their northern range

Abstract

Migration functions as an adaptive strategy to improve fitness by allowing individuals to exploit spatiotemporal gradients of resources. Yet migration, especially among large ungulates, is increasingly threatened by human activities, making it necessary to understand variation in migratory behavior. We identified different movement strategies for pronghorn (Antilocapra americana) at the northern limit of the species’ range, and tested hypotheses for variation between migratory behaviors. From 2003–2010, we captured 185 female pronghorn across Alberta and Saskatchewan, Canada, and Montana, USA. We identified discrete migratory behaviors, including seasonal migration, facultative winter migration, potential post‐fawning migration, and the use of stopover sites. Fifty‐five percent of individuals undertook seasonal migrations, and we recorded the longest reported round‐trip migration for the species at 888 km. Some (22%) seasonal migrations included ≥1 stopover sites, with significantly greater use of stopovers during spring than fall. Migrants (34%) and residents (20%) undertook facultative winter migrations, with the majority (68%) undertaken by migrants. Additionally, 12% of individuals exhibited potential post‐fawning migrations. For each season, we estimated a suite of movement metrics and used multivariate statistics to compare movement similarities across migration behaviors. Correspondence analyses revealed 3 groupings of migration behavior. Spring migration was its own grouping, characterized by more sinuous and slower movements, consistent with the forage maturation hypothesis. Fall migration, facultative winter migration, and potential post‐fawning migration clustered in a single group that displayed linear, fast movements, consistent with being influenced by ecologically limited resources such as severe winters or predation avoidance. Lastly, spring and fall stopover sites were grouped together as a means to use high‐quality forage during migration, also consistent with the forage maturation hypothesis. At the northern periphery of pronghorn range, differences between migratory behaviors are influenced by various ecological factors, merit increased attention, and contribute to overall persistence. © 2018 The Wildlife Society.

Fences reduce habitat for a partially migratory ungulate in the Northern Sagebrush Steppe

“…The study area experienced severe winter conditions from 2008 to 2011, especially during the winter of 2010–2011, when mean temperatures were below average and snow accumulation broke regional records (Jakes et al. ).…”

“…, Jakes et al. ). Studies of partially migratory populations can provide key insights into behavioral and fitness consequences between movement tactics (Cagnacci et al.…”

Where to spend the winter? The role of intraspecific competition and climate in determining the selection of wintering areas by migratory caribou

“…Usually viewed as a predictable displacement between a specific breeding area and a specific non‐breeding area (Newton ), migratory movements can nevertheless show interannual variations and may vary between individuals in terms of direction and distance travelled (Berthold et al , Bauer et al ). In ungulates, although migration can be a fixed behaviour (Sawyer et al ), migratory plasticity has received increasing support in recent years (Mysterud et al , Eggeman et al , Jacks et al , Spitz et al ) and flexibility in migratory behaviour has been observed in individuals switching between different migratory strategies (Morrison and Bolger , Eggeman et al , Spitz et al ). Such variability makes the conservation of highly mobile species particularly challenging (Runge et al ).…”

“…At the individual level, flexibility in migratory behaviour allows individuals to adjust their migratory strategies switching between migrant and resident status according to the expected gain in fitness of each tactic (Eggeman et al ). Flexibility in migratory behaviour reflects the effects of environmental conditions observed at the population level because individuals switch from residents to migrants based on competition and resources availability (Eggeman et al , Jacks et al ). Such flexibility in migratory behaviour allows individuals to be more resilient to environmental changes (Gilroy et al ) and less exposed to perturbations than individuals in populations with fixed migratory behaviour (Harris et al , Sawyer et al ).…”

Long‐term effects of energy development on winter distribution and residency of pronghorn in the Greater Yellowstone Ecosystem

“…Pronghorn on the other hand, utilize a much larger swath of winter range habitats (~125 km 2 ; Figure 1) and move about often and unpredictably (Bruns, 1977;Collins, 2016;Kolar, Millspaugh, & Stillings, 2011;Sawyer, Lindzey, & McWhirter, 2005). The challenges associated with detecting behavioral changes in highly mobile species can be accentuated by short-term study, especially in regions prone to variable weather events and environmental conditions (e.g., Jakes et al, 2018). The challenges associated with detecting behavioral changes in highly mobile species can be accentuated by short-term study, especially in regions prone to variable weather events and environmental conditions (e.g., Jakes et al, 2018).…”