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

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.