A squirrel runs with a vole in its mouth at Briones Regional Park, California. (Photo: Sonya Wild, University of California, Davis)
Gophers primarily feed on seeds and nuts, but in a California park, these cute, furry creatures have become predators, mercilessly hunting voles to rip the meat from their bones.
The unusual behavior, recorded by scientists at Briones Regional Park in Contra Costa County, may be linked to a surge in vole populations, according to a new study published in the Journal of Ethology on Wednesday (Dec. 18).
Students have been monitoring squirrels in Briones Regional Park for 12 years as part of a long-term research project organized by the University of Wisconsin-Eau Claire and the University of California, Davis. In all their research, they have never encountered what they saw in the summer of 2024.
The study's lead author, Jennifer Smith, an assistant professor of biology at the University of Wisconsin-Eau Claire, is one of the leaders of a park project called Squirrel Team. When two students first showed her videos of predatory squirrels, she was confused.
“I was amazed, in disbelief, and frankly, incredibly excited to learn more about what was going on,” Smith told Live Science in an email. “My first question was whether squirrels were hunting voles in the area. The Squirrel team made it their mission to document every hunt, kill, and consumption event from start to finish using digital photography of these predatory squirrels.”
The squirrel family is known to have considerable flexibility in its diet. California ground squirrels (Otospermophilus beecheyi) are primarily vegetarians, but studies have shown that they also consume insects, eggs, chicks, and even their own young. However, actively hunting adult mammals represents a significant change in squirrel behavior.
The team observed squirrels hunting California voles (Microtus californicus californicus) nearly every day from June 10 to July 30, indicating that the behavior has become fairly common this year. A typical hunt involved the gopher chasing the vole and biting it, most often on the neck or head, Smith said.
“Not all hunts were successful, but once caught, the squirrels would typically start by eating the head – bones included – and then move on to picking the voles' bones,” Smith added.
In some cases, one squirrel would catch a vole, and then another squirrel would come along to try to steal its catch. The study authors noted that this competition for meat led to aggressive interactions among the squirrels.
Why do squirrels kill voles?
The squirrel activity coincided with a surge in the local vole population. Some vole populations remain stable, but most fluctuate in a multi-year cycle, peaking every three to five years, according to the study. California's vole population appears to have hit a record this year, with significantly more voles recorded than in previous years — about seven times the average for the past 10 years.
The study's authors attribute the squirrels' new hunting behavior to this surge in available voles. Smith noted that voles are unlikely to be as plentiful next year, so the squirrels will likely return to eating seeds.
The Squirrel team will continue to monitor the squirrels next year to better understand the impact of this hunting behaviour.
“One of the most interesting next steps will be to understand the consequences for survival and reproduction in response to this predatory behavior,” Smith said. “Squirrels, like most rodents, are what we call ‘income producers.’ Large amounts of food, especially high-quality meat, should lead to larger numbers of offspring.”
Sourse: www.livescience.com
