Institute for Marine Mammal Studies veterinary technician Wendy Hatchett takes a skin sample from a dead bottlenose dolphin that was found on Ono Island, Ala., and brought for examination to Gulfport, Miss., on Tuesday. Patrick Semansky/AP hide caption

itoggle caption Patrick Semansky/AP

Researchers found that as groups of black-tailed prairie dogs and other rodents became larger, it also became easier to identify individuals. Kimberly Pollard/UCLA hide caption

itoggle caption Kimberly Pollard/UCLA

Some 16,000 years ago, people may have been curling up next to the fire with red foxes. iStockphoto.com hide caption

itoggle caption iStockphoto.com

An American black bear from the Kenai Peninsula in Alaska. A new study found that a bear's metabolism in hibernation drops by nearly 75 percent while its body temperature falls just slightly. Oivind Toien/Institute of Arctic Biology, University of Alaska, Fairbanks hide caption

itoggle caption Oivind Toien/Institute of Arctic Biology, University of Alaska, Fairbanks

A mature Atlantic tomcod collected from the Hudson River. These tomcod evolved to handle excessive amounts of industrial pollutants, like PCBs and dioxin, in the water. Science/AAAS hide caption

itoggle caption Science/AAAS

Daisy Mae, a miniature Vietnamese potbellied pig, lounges on a couch in West St. Paul, Minn. Vincent J. Musi/National Geographic hide caption

itoggle caption Vincent J. Musi/National Geographic

The crew of the whaling vessel Yushin Maru #3 uses their water cannons against Sea Shepherd's Delta team (foreground) in a Zodiac boat during clashes in the Southern Ocean. The photo was taken on Jan. 1 by the Sea Shepherd Conservation Society. Gary Stokes/AFP/Getty Images hide caption

itoggle caption Gary Stokes/AFP/Getty Images

Fleas push off the ground from the ends of their legs, not from the part of the leg that resembles a knee. Gregory Sutton hide caption

itoggle caption Gregory Sutton

The Pacific walrus has to wait to be placed on the endangered species list. AP hide caption

itoggle caption AP

Researchers have sequenced the genome of the common water flea, Daphnia, shown in this false-color micrograph. About 35 percent of the genes are brand new to science. Jan Michels/Christian-Albrechts-Universitat zu Kiel hide caption

itoggle caption Jan Michels/Christian-Albrechts-Universitat zu Kiel