Toucan’s ‘Sexual Ornamentation’ Moderates Body Temperature

http://www.bloomberg.com/apps/news?pid=20601124&sid=aA8HykidbSto

By Jeremy van Loon and Alex Morales
July 24 (Bloomberg) -- Heating and cooling takes on a new meaning in the toucan’s world. That’s because the bird’s overly large beak, speculated by Charles Darwin to be a sexual ornament, actually regulates temperature, scientists have found.

The distinctive bill makes up a third of the toucan’s body length, surpassing elephant ears in the ability to rapidly radiate body heat, researchers said. The beak adjusts the bird’s temperature by as much as 15 degrees Celsius (27 degrees Fahrenheit), said Glenn Tattersall, a biologist at Brock University in St. Catharines, Ontario, and lead author of the study that appeared yesterday in the journal Science.

Animals in addition to toucans have a range of ways to stay cool or keep warm in harsh environments, including layers of fat in polar bears and large skin surfaces in elephants. Tattersall and colleagues discovered the toucan can lose up to four times as much heat from its colorful beak than it produces at rest -- the most reported for any animal.

“The bill can act like a thermal window or thermal radiator that allows it to release or conserve body heat,” Tattersall said in a podcast on Science’s Web site.

Various explanations have been posited for why the toucan’s bill is so large, including its use in peeling fruit, warding off enemies or, according to Darwin, renown for positing a theory of evolution in “On the Origin of Species,” as a way to attract a mate.

Darwin’s Assumption

“Toucans may owe the enormous size of their beaks to sexual selection, for the sake of displaying the diversified and vivid stripes of color with which these organs are ornamented,” Darwin wrote, the study said.

Tattersall worked with scientists at Brazil’s National Institute of Science and Technology in Comparative Physiology and at Sao Paulo State University. The researchers used thermal imaging to measure the surface temperature of the toco toucan’s bill in a range of air temperatures. The heat loss from the appendage was “highly variable,” ranging from 25 percent to 400 percent of resting heat production in adult birds, they wrote. The upper limit is more than four times as much elephant ears and duck beaks, according to the study.

As toucans fall asleep, an activity that requires lower body temperature, the beak releases the heat from the rest of the body via blood vessels, Tattersall said. During flight, the bird is able to release heat from flapping its wings through its bill as well, he said. The birds, however, are not known for their flying prowess.

I think that should be "the bird is able to release heat from flapping its wings as well as through its bill.

I've certainly made my share of typos after changing the wording of comments on other blogs, and not checking carefully, or overlooking, such errors.

The toco toucan, whose Latin name is Ramphastos toco, is found from Guyana and Suriname to Argentina and Paraguay in South America, according to Cambridge, England-based Birdlife International, an alliance of conservation groups worldwide.