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Dryad

Sex-specific selection of agricultural farmland by a partially migratory ungulate

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Feb 26, 2025 version files 190.59 MB

Abstract

Large herbivores at northern latitudes often forage on agricultural farmland. In these populations, presence of both resident and migrant individuals (termed partial migration) is common, but how migrants and residents differ in their selection of farmland is not well understood. Higher access to farmland may provide benefits to residents compensating for not following the ‘green wave’ of emerging vegetation like migrants. According to sexual segregation theory, males and females differ in body-size related nutritional needs and risk-sensitivity associated with farmland. Yet, how the sexes differ in selection of farmland through an annual cycle remains unclear.

We quantified seasonal variation in the selection of farmland by partially migratory red deer (Cervus elaphus) at broad, landscape scale and at fine, within-home range scale using 16 years of data (2005-2020) from 329 females and 115 males in Norway.

We tested predictions related to the partial migration and sexual segregation theories using resource selection functions. We predicted higher selection for farmland by residents than migrants, and higher selection by females than males due to higher nutritional needs, but that higher perceived predation risk would impact their diurnal selection patterns.

The time spent on farmland was higher in winter (14-18%) than summer (8-14%). Residents selected farmland more than migrants mainly at broad, landscape scale, while differences were smaller and less consistent at fine, within-home range scale. Females showed higher broad-scale selection for farmland in winter, and males higher in summer. At fine, within-home range scale, females selected farmland more in summer during darkness, whereas sex-differences were small otherwise. The fine-scale selection of farmland was markedly higher during low-light conditions than during daylight. High population density was correlated with high broad-scale selection of farmland, i.e., high farmland availability in the home ranges, whereas the effect of density was weak at fine, within-home range scale.

Our study emphasises how hypotheses deriving from the theories of partial migration and sexual segregation can improve our understanding of selection of farmland by ungulates. The higher selection by residents during summer highlights the importance of retaining landscape connectivity allowing for migration, reducing pressure on local resources.