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| A family of Burrowing Owls (By travelwayoflife (Flickr: Owl Family Portrait) [CC BY-SA 2.0 (https://creativecommons.org/licenses/by-sa/2.0)], via Wikimedia Commons) |
For many years it was thought that only humans used tools.
Then chimpanzees were seen using sticks to get termites and folding leaves into
cups to hold water. After that it was
reluctantly agreed that tool use was not
uniquely human, but that it certainly was restricted to the great apes, mankind’s
closest relatives. Then ornithologists reported that many birds engaged in
activities considered to be tool use; e.g., the Galapagos woodpecker finch
shapes twigs and cactus spines to pry insects out of their hiding places. Other
birds use rocks to break open ostrich eggs and several herons throw objects onto
the water surface to attract their fish prey. And now the Burrowing Owl can join
the tool using club.
True to its name, the Burrowing Owl inhabits burrows in pastures,
rangeland, golf courses and other open spaces with low or sparse vegetation. Unlike
other owls it is active during the day and night and can be seen standing in or
near the opening of its burrow. In the west they are primarily found in
prairie dog towns; in the east they were formerly found in pastures and golf
courses inhabited by ground squirrels. Some populations still survive in
Florida. Like other small owls they feed on insects and small mammals.
In a colony of burrowing owls University of Florida researchers noticed
a curious thing: the burrow entrances were “decorated” with mammalian dung.
This was not an accident because when the investigators removed the dung it was
soon replaced. But why? At least two possibilities suggest themselves: The odor
of the dung might mask the presence of young owls or eggs from predators, or
the dung could attract dung beetles, potential food for the owls.
The first possibility was tested by placing quail eggs
in vacant burrows. Then dung was collected and placed around half the burrows that
had quail eggs. If the dung masked the scent of eggs there should be less
predation on the dung-protected burrows. But the results showed that eggs were
equally likely to be eaten whether the burrow was “protected” or not.
To test the food attraction idea the researchers removed all
the dung and other prey remains from all the active burrows and then replaced
the dung in half the burrows with an equivalent amount of cow manure. Four days
later they returned to the owl colony and searched the area around each burrow
for prey parts and "owl pellets" to see what the owls had been
eating. (Like other owls, the Burrowing Owl regurgitates the indigestible parts
of its food in a compact mass called the "owl pellet." These pellets
contain the fur and bones of the rodents the owl has eaten as well as pieces of
insect exoskeletons. All can be identified by teasing apart the pellet.)
The burrows decorated with cow dung had pellets that
contained 10 times more dung beetle parts and 6 times more dung beetle species than
those without dung.
So the answer to the question posed in the title of this post is: like the herons, you can fish using dung for bait.
References:
Levey, D.J., Duncan, R.S., and Levins, C.F. (2004).
Animal behaviour: Use of dung as a tool
by burrowing owls. Nature 431, 39–39.
