Artificial selection for predatory behavior results in dietary niche differentiation in an omnivorous mammal

The diet of an individual is a result of the availability of dietary items
and the individual's foraging skills and preferences. Behavioral
differences may thus influence diet variation, but the evolvability of
diet choice through behavioral evolution has not been studied. We used
experimental evolution combined with a field enclosure experiment to test
whether behavioral selection leads to dietary divergence. We analysed the
individual dietary niche via stable isotope ratios of nitrogen (δ15N) and
carbon (δ13C) in the hair of an omnivorous mammal, bank vole, from 4 lines
selected for predatory behavior and 4 unselected control lines. Predatory
voles had higher hair δ15N values than control voles, supporting our
hypothesis that predatory voles would consume a higher trophic level diet
(more animal vs. plant foods). This difference was significant in the
early but not the late summer season. The δ13C values also indicated a
seasonal change in the consumed plant matter and a difference in food
sources among selection lines in the early summer. These results imply
that environmental factors interact with evolved behavioral tendencies to
determine dietary niche heterogeneity. Behavioral selection thus has
potential to contribute to the evolution of diet choice and ultimately the
species' ecological niche breadth.