Voles Trim Tall Grass to Prevent Attacks

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Tiny rodents native to the plains of Inner Mongolia in China have been spotted trimming tall grasses to prevent predators from perching near their nests. A study published in Current Biology on Friday (March 11) found that the animals, known as Brandt’s voles (Lasiopodomys brandtii), actively shape their environments to make them safer, an example that experts call “ecosystem engineering.”

The voles’ primary predators are shrikes (Lanius spp.), also known as butcherbirds, which are notorious for their gruesome habit of impaling their prey on a thorn or twig to eat later or attract mates. Shrikes use bunchgrass, a tall, bladed grass that usually grows in discrete tufts, as perches when hunting and as sites to store prey for later consumption, the authors write in the paper.

The study was a collaborative effort between researchers in China, the UK, and the US. Using a combination of field surveys and manipulations, the researchers found that voles trim the bottom part of bunchgrass stems when shrikes are nearby. They also dig burrows that destroy bunchgrass roots.

While voles don’t consume the bunchgrasses, damaging them gives shrikes fewer places to perch and thus fewer chances to sneak up on unsuspecting prey, the researchers tell Psychology Today.

“This led to fewer visits from shrikes, which apparently recognize cut-grass areas as poor hunting grounds,” ecologist Dirk Sanders of the University of Exeter, one of the study’s authors, explains to The Guardian. “An activity like this is costly for the voles in terms of energy so cutting the grass must significantly improve their chances of survival.” 

When Sanders and his colleagues put nets up over certain areas to keep shrikes out, the voles there stopped cutting the bunchgrass. “These voles actually change their behavior when they perceive the risk of predators and alter their habitat to reduce the predation risk,” Sanders tells Psychology Today. This experiment illustrates that the grass-cutting behavior is likely adaptive, Sanders explains.

Sanders and his colleagues tell Psychology Today that this behavior enters voles into a category of animals that can change their environments, putting them alongside beavers and earthworms. Scientists have previously documented other so-called ecosystem engineers, such as African elephants, which clear savannas of brush and make it harder for predators to stalk prey. However, this is the first time scientists have documented a species changing its environment to decrease its own predation risk, Sanders tells the outlet

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