Burrowing owls use dung to catch dinner.© SPLIt is unlikely to win an award for tasteful home decor, but the burrowing owl has a good reason for filling its lair with other animals' muck. The birds scatter scraps of faeces in and around their burrows to attract dung beetles, one of their favourite foods.
The birds' 'bait and wait' strategy represents a form of tool use, say Douglas Levey of the University of Florida in Gainesville and his colleagues, who made the discovery. Although dung might not be everyone's idea of a useful tool, the fact that the birds gather and arrange it means that it can be defined as such.
Levey and his team observed a group of the owls (Athene cunicularia), which live throughout North and South America, to see whether the presence of dung outside their burrows had any influence on their diet. After removing the dung from all of the burrows, the researchers placed fresh faeces in front of some of them and left the rest bare.
After four days, the team examined the debris in and around the nests for tell-tale fragments of beetle carcass. As they report in this week's Nature1, owls with dung outside their homes feasted on ten times more dung beetles than those without.
Automatic for the beetle
The owls tend to collect dung produced by local mammals, which can be anything from horses and cows to cats, dogs or even antelope, says Levey. But the fact that they use faeces as bait does not necessarily mean they are consciously plotting to catch beetles. "A lot of people have an image of owls as wise, but I do not think the owls are aware of what they are doing," he says.
“A lot of people have an image of owls as wise, but I don't think the owls are aware of what they're doing”
Douglas Levey
University of Florida in Gainesville
The behaviour probably evolved to benefit the owls without them knowing why, agrees Bernd Heinrich, an expert on bird tool-use at the University of Vermont in Burlington. "The acts of putting down the dung and getting the beetles are probably too far apart in time for the owls to reason it out," he argues.
Indeed, Levey suspects that the behaviour may have arisen for some other reason, such as to disguise the smell of chicks or to create an impressive visual display to entice females. "I don't think dung beetles are the whole story," he says.
The owls are notorious collectors of junk, including aluminium cans, scraps of carpet and even animals killed on the roads, such as toads. Perhaps dung started out as just another collectable, and the habit was reinforced by the fact that it also attracts food, Levey speculates.
University of Florida in Gainesville
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