FOR KIDS: The secret songs of giant beavers

 During the last Ice Age, which ended about 10,000 years ago, oversized animals like the giant beaver roamed North America. The skeleton shown here is on display at the Field Museum in Chicago.C. Horwitz

Giant beavers, which vanished from North America about 10,000 years ago, had a secret in their heads: a long compartment that stretched from front to back in the animals' skull. Caroline Rinaldi, a paleontologist who studies extinct mammals, may have figured out the chamber's purpose. She recently presented her ideas to a meeting of scientists in Las Vegas, using a plastic copy of the skull's hidden tunnel to demonstrate her surprising find.