Owls have a reputation for being brainy birds. Now new research published in the 2 September issue of Nature shows that one kind of owl employs an unlikely kind of bait to help catch its dinner.
Burrowing owls (Athene cunicularia) have curious taste in home decor: They adorn the interiors and doorsteps of their underground tunnels with stinky heaps of assorted mammal dung. Because the owls apply dung more often during the spring breeding season, zoologist Douglas Levey of the University of Florida, Gainesville, and colleagues suspected that the smelly stuff might serve as olfactory camouflage for their vulnerable young. But the presence of dung didn't protect quail eggs stashed in artificial burrows, the researchers discovered; predators ate the eggs in all but one of 50 cases. So the scientists considered another hypothesis.
Burrowing owls consume all manner of small creatures, but dung beetles are a staple. Could dung help lure the owls' favorite food? To test this idea, the scientists first stripped all dung, owl pellets, and beetle parts from 10 burrows belonging to two colonies of owls. They then added cow dung back to burrows in one colony while leaving burrows in the second colony bare. After 4 days, the researchers collected prey remains and regurgitated owl pellets near the burrow entrances, then repeated the experiment, switching conditions between colonies. The remains of the owls' meals showed that the birds ate 10 times as many dung beetles when their burrows were surrounded by cow manure. "The owls spend a lot of time standing right by their burrows," Levey says. "It's like they've got a line in the water like fishermen, and they're sitting waiting for something to come."The study builds an elegant case that the owls are using the dung as a tool, says Gavin Hunt of the University of Auckland, New Zealand, who studies toolmaking in crows. "It's probably the first study that's had a good go at quantifying the importance of tool use in the wild." Still, behavioral ecologist Alex Kacelnik of Oxford University, United Kingdom, doesn't see evidence of inductive reasoning or creative problem solving. "In some sense this is what a spider does when it builds a web; it's a very sophisticated behavior but is in no way an individual invention."