Voles cut grass to reduce their predation risk

Brandt’s voles are tiny rodents living in grasslands in Inner Mongolia, China, where they are usually hunted by birds called shrikes. A new study published in the journal Current Biology has found that the voles often cut tall bunchgrass when shrikes are nearby so they can observe the approach of the predators and hide faster. 

Since they never eat the grass or use it in any specific way, researchers argue that this behavior should be seen as an example of “ecosystem engineering” through which voles aim to keep themselves safe.

“When shrikes were present, the voles dramatically decreased the volume of bunchgrass,” said study co-author Dirk Sanders, a research fellow in Ecology at the University of Exeter. “This led to fewer visits from shrikes – which apparently recognize cut-grass areas as poor hunting grounds. An activity like this is costly for the voles in terms of energy, so there must be high ‘selection pressure’ to do it – cutting the grass must significantly improve their chances of survival.”

By putting up nets over certain areas, the scientists also tested what impact keeping the birds away has on voles’ behavior. They found that, with no shrikes overhead, the voles stopped cutting the bunchgrass.

“We sometimes underestimate the ability of wild animals to react to changes in their environment. In this case, the voles were able to change their behavior in response to the removal of predators,” explained Dr. Sanders. “Our findings are a reminder that species show remarkable adaptations. It also underlines that the loss of even a single species in a food web can result in unexpected changes to an entire habitat.”

These findings suggest that animals can actively modify their habitats to reduce predation risk through ecosystem engineering. Moreover, it could also have important implications for rodent management in pasture lands. In this particular case, keeping or even planting large bunchgrasses could help attracting avian predators such as shrikes and thus reduce the population density of voles.

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By Andrei Ionescu, Earth.com Staff Writer