Functional attributes of ungulate migration: landscape features facilitate movement and access to forage

Abstract

Long‐distance migration by terrestrial mammals is a phenomenon critical to the persistence of populations, but such migrations are declining globally because of over‐harvest, habitat loss, and movement barriers. Increasingly, there is a need to improve existing routes, mitigate route segments affected by anthropogenic disturbance, and in some instances, determine whether alternative routes are available. Using a hypothesis‐driven approach, we identified landscape features associated with the primary functional attributes, stopovers and movement corridors, of spring migratory routes for mule deer in two study areas using resource selection functions. Patterns of selection for landscape attributes of movement corridors and stopovers mostly were similar; however, landscape features associated with movement corridors aligned better with areas that facilitated movement, whereas selection of stopovers was consistent with sites offering early access to spring forage. For movement corridors, deer selected for dry sites, low elevation, and low anthropogenic disturbance. For stopovers, deer selected for dry sites, with consistently early green‐up across years, south‐southwesterly aspects, low elevation, and low anthropogenic disturbance. Stopovers and movement corridors of a migratory route presumably promote different functions, but for a terrestrial migrant, patterns of habitat selection indicate that the same general habitat attributes may facilitate both movement and foraging in spring. Our findings emphasize the roles of topographical wetness, vegetation phenology, and anthropogenic disturbance in shaping use of the landscape during migration for this large herbivore. Avoiding human disturbance and tracking ephemeral forage resources appear to be a consistent pattern during migration, which reinforces the notion that movement during migration has a nutritional underpinning and disturbance potentially alters the net benefits of migration.

Spatial memory shapes migration and its benefits: evidence from a large herbivore

“…Relatedly, the classic definition of habitat is based on static, environmental characteristics of a location such as vegetation or cover type (Hall et al 1997;Morris 2003). Based on our results and other studies documenting the influence of past experience on animal movement (Fagan et al 2013), it is becoming clear that the habitat concept should be re-conceptualised as an interaction among extrinsic environmental characteristics, and the knowledge an animal possesses of a place (Merkle et al 2015), including when it is available or advantageous to use that place (Armstrong et al 2016;Monteith et al 2018). Without embracing such a comprehensive framework, terms such as migration habitat can be misleading.…”

“…For mammals, the only evidence of memory‐based migration has come from zebra (Bracis & Mueller ) and blue whales (Abrahms et al ). Most studies suggest that migratory behaviour could simply emerge from tracking resource waves across large landscapes, where individuals follow cues within their perceptual range that change predictably along seasonal gradients (Avgar et al ; Lendrum et al ; Armstrong et al ; Monteith et al ). For example, mammals such as Mexican long‐nosed bats (Moreno‐Valdez et al ) and West Indian manatees (Deutsch et al ) appear to track waves of food or thermal conditions during migration.…”

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

“…, Monteith et al. ). Declines in migratory ungulates can affect ecosystem function, including nutrient flow, predator–prey dynamics, and biodiversity processes (Berger , Bolger et al.…”

“…For example, Tucker et al (2018) showed for 57 mammalian species that movements in areas of high human footprint averaged one-half to onethird the extent of their movements compared to areas of low disturbance. Migratory ungulates are especially vulnerable to anthropogenic impacts as they often travel across large and diverse landscapes of varying land ownership (Berger 2004, Harris et al 2009, Seidler et al 2015, Monteith et al 2018. Declines in migratory ungulates can affect ecosystem function, including nutrient flow, predator-prey dynamics, and biodiversity processes (Berger 2004, Bolger et al 2008.…”

All routes are not created equal: An ungulate's choice of migration route can influence its survival

“…Recent studies have also highlighted the important functional role that migratory routes play in the annual nutritional cycle of large herbivores by providing foraging and resting habitat (Monteith, Hayes, Kauffman, Copeland, & Sawyer, ; Sawyer & Kauffman, ). The recognition that migratory habitat is functionally important for nutrition as well as movement (Aikens et al, ) carries an implicit, but rarely examined assumption that habitat quality, predation risk, human disturbance and other factors should vary within and among migratory routes.…”