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Who can figure out the toucan? You can!

Adult Toco toucan.
[Image courtesy of Thiago Filadelpho]

The toco toucan's bill occupies a special place in the hall of animal oddities.

Making up about one-third of the bird's total body length, it's the largest bill of any bird, compared to its owner's body size. Scientists have puzzled for centuries over the bill's possible purpose. Might be used for attracting mates? Maybe for manipulating fruit?

Now, a team of researchers has another explanation. Like the elephant's ear, the toucan's bill may operate as a remarkably efficient radiator that dumps body heat when the bird needs to cool down.

As revealed from thermal imaging, toucans can restrict blood flow to the bill when cold, and when warm, can increase blood flow to remove heat.
[Image courtesy of Glenn Tattersall]

To discover this, Glenn Tattersall of Brock University in Canada and colleagues monitored toucans with heat-sensing cameras while the birds were exposed to different air temperatures.

The researchers observed that the bill's surface temperature changed quickly as its environment warmed or cooled. For example, at sunset, as the birds were going to sleep, the bills cooled by about 10 degrees Celsius within minutes.

The birds thus appear to use their bills, which have many blood vessels that bring heat near the bill's surface, to radiate heat so that the animals can reduce their body temperature during sleep. In their study, the authors speculate that other birds, which can't sweat, after all, may also use their bills for this purpose.


This research appears in the 24 July issue of the journal Science.