Sex‐dependent habitat selection modulates risk management by meadow voles

Abstract

Foraging involves a trade‐off between food and safety. Most research into the trade‐off invokes safety from predation. But danger and its associated risk arise from multiple causes that cannot be assessed solely with reference to predators. A more complete assessment of risk management requires experimental designs that attempt to modify and measure risks, regardless of the source of danger. I aimed to do so by adding shelter (mulched straw) and time‐varying supplemental food (rabbit chow), while measuring foraging behavior and habitat use by a seminatural population of meadow voles. Voles foraged more intensely under safety, recognized least risk when given access to both food and shelter, but altered their risk management through time: management included a novel form of sex‐dependent habitat selection in which male–male pairs occupied risky areas without shelter while female–female pairs occupied habitats sheltered by straw. The pattern is consistent with a sex‐dependent evolutionary game in which female territoriality and tolerance of other females limit conflict with, and space use by, males. Voles' array of interacting strategies demonstrates that ecologists must be wary of ascribing risk only to predation, and particularly so if experiments are blind to other dangers and processes that alter foraging behavior and habitat selection.

Adaptive responses to habitat change: Theory and tests with field experiments

“…Dividing the remaining GUDs by the largest GUD produced the remaining fitness proxies (0 ≤ fitness estimate ≤ 1). I made the simulations comparable to those in Figures 1 and 2 by assuming that each enclosure's four equal‐sized patches (Figure 3) would saturate at 10 individuals each (an earlier experiment documented that equal numbers of voles occupied the four patch types [Morris, 2023]). The population size is thus standardized at 15 times the initial vole densities used in the actual field experiment: the simulated ADSLs are properly interpreted as representing reliable shapes of the voles' adaptive advantage of habitat selection rather than absolute values.…”

“…We randomly assigned the four patch types to each of the four permanent stations in enclosure 13, then used the same arrangement in adjacent enclosure 14 (Figure 3, also illustrated for one enclosure in fig. 1 of Morris, 2023). We placed two plastic foraging trays containing 8 g of whole oats mixed thoroughly in 1.5 L of sieved dry silica sand under either a polyethylene-covered (= risky) or plywood-covered (= safe) shelter that protected foraging trays from wind and rain.…”

“…Dividing the remaining GUDs by the largest GUD produced the remaining fitness proxies (0 ≤ fitness estimate ≤ 1). I made the simulations comparable to those in Figures 1 and 2 by assuming that each enclosure's four equal-sized patches (Figure 3) would saturate at 10 individuals each (an earlier experiment documented that equal numbers of voles occupied the four patch types [Morris, 2023]).…”