SSS 2009-07-27（在线收听）

The toucan's long bill has long perplexed biologists. Darwin theorized that it attracted mates. Other suggested uses ranged from fruit peeling to territorial defense. But a report in the July 24th issue of the journal Science offers another explanation as to why one-third of the bird is all schnoz. The authors of the report say the toucan's bill is so big because it acts like a radiator strapped to its face. When a toucan needs to cool down, its beak heats up. The immense surface area of the beak allows heat to quickly dissipate. In fact, the scientists say, as a toucan lowers its body temperature in preparation for sleep, it can cool 10 degrees Celsius in just minutes.

The scientists used infrared thermography, the same kind of technology used in heat-sensing cameras, to observe toucans at different ambient temperatures. When outside temperatures rose, the bill also heated up, but the bird’s core body temperature did not. The scientists speculate that other big-billed birds may regulate their body temperatures this way. Since birds don’t sweat, having a handy heat dissipater undoubtedly keeps their feathers from getting ruffled.