This young mountain yellow-legged frog, seen in San Bernardino County, Calif., is less than 1 1/2 inches long. Adults measure about 2 to 3 inches long. Scientists are trying to revive the frog population that has been decimated by drought, fire and diseases. USGS hide caption

itoggle caption USGS

As winter approaches, Bill Thompson gave Melissa Block's backyard in Washington, D.C., a bird feeding makeover. "It's the time of year most folks start feeding actively, cause we get a lot of the northern birds coming down for the winter, to what they feel is our milder climate," he says. Here, an Eastern bluebird sits on an icy feeder. Bill Thompson III hide caption

itoggle caption Bill Thompson III

Famed Taxidermist Carl Akeley and the leopard he killed with his bare hands.

Field Museum of Natural History hide caption

itoggle caption Field Museum of Natural History

Troops crowd President Obama during his visit to Bagram Air Base in Afghanistan on Friday. Jim Watson/Getty Images hide caption

itoggle caption Jim Watson/Getty Images

Mono Lake, Calif., is home to a bacterium discovered by NASA scientists that can eat and grow on arsenic instead of phosphorous, one of the basic building blocks of life. The finding has implications for NASA's ongoing search for signs of life elsewhere in the universe. David McNew/Getty Images hide caption

itoggle caption David McNew/Getty Images