Native forage mediates influence of irrigated agriculture on migratory behavior of elk

1. Ungulates migrate to maximize nutritional intake when forage varies seasonally. Populations of ungulates often include both migratory and non-migratory individuals, but the mechanisms driving individual differences in migratory behavior are not well-understood. 2. We quantified associations between hypothesized drivers of partial migration and the likelihood of migration for individual ungulates that experienced a range of environmental conditions and anthropogenic influences. 3. We evaluated the effects of forage variation, conspecific density, and human land uses on migratory behavior of 308 adult female elk in 16 herds across western Montana. 4. We found irrigated agriculture on an individual’s winter range reduced migratory behavior, but individuals were more likely to migrate away from irrigated agricultural areas if better forage was available elsewhere or if they experienced high conspecific density on their winter range. When the forage available during the summer growing sea...