for National Geographic News
Burrowing owls have an affinity for the dung of other animals. Their underground nests and surrounding areas are carpeted with the stinky stuff. Now a team of researchers has found at least one reason why all this fecal matter matters to the owls: It's bait for dung beetles, the owls' favorite grub.
The research, reported in today's issue of the science journal Nature, demonstrates that burrowing owls (Athene cunicularia) deliberately use mammal dung as a tool to reel in a mealand in the process substantially increase the number of dung beetles they eat.
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"Burrowing owls are diurnal [active in daytime], they will sit at the burrow entrance all day long and it looks like they're doing nothing," said Douglas Levey, a zoologist at the University of Florida in Gainesville. "But you know what? It's pretty clear they are fishing. They've got their line in the water and are waiting for dung beetles to come by."
Levey, who is the lead author of the study, added that the finding is particularly noteworthy because it demonstrates that tool use can substantially benefit a wild animal. Such convincing evidence is scant in the biological record.
For example, herons are widely known to place a floating object, such as a bread crumb or feather, on top of water as a lure for minnows. But no studies have compared how well herons would do if they did not fish in this manner.
"As far as I know, [our study] is the first example of that, not just in birds but in wild animals in general," Levey said.
Gavin Hunt, an ecologist at the University of Auckland in New Zealand who studies tool use by crows, agrees.
"The owl paper is the first to really quantify the benefit of tool use to a free-living animal in terms of food gained," he said. "As such, it is an interesting finding that seems to confirm what most of us have only assumed to date."
The researchers came up with the study idea several years ago while on a field trip to observe burrowing owls. It was part of an ornithology course Levey was teaching at the University of the Florida.
Levey and his studentsincluding study co-authors Scot Duncan, now at Birmingham-Southern College in Alabama, and Carrie Levins, who lives in Panama City, Floridanoticed dung scattered around the burrow and wondered why it was there.
Duncan, whose wife happens to be a beetle expert, recognized beetle parts in the regurgitated pellets that were mixed in with the dung. He realized that the owls were eating a bunch of beetles.
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