Squirrels closely mimic bird warning calls and help spread the alarm through the forest that hawks, owls or other predators are nearby. iStockphoto hide caption

itoggle caption iStockphoto

There are about 400,000 greater sage grouse left on the landscape, spread across 11 Western states, from California to North Dakota. That's a fraction of what their numbers were just a century ago. Tom Koerner/U.S. Fish and Wildlife Service hide caption

itoggle caption Tom Koerner/U.S. Fish and Wildlife Service

Two octopuses going at it — or, as marine biologist Peter Godfrey-Smith might put it, engaging in a bit of "ornery" behavior. Peter Godfrey-Smith (CUNY and University of Sydney), David Scheel (Alaska Pacific University), Stefan Linquist (University of Guelph) and Matthew Lawrence. hide caption

itoggle caption Peter Godfrey-Smith (CUNY and University of Sydney), David Scheel (Alaska Pacific University), Stefan Linquist (University of Guelph) and Matthew Lawrence.

California condors have enormous wingspans. That's fine in the wilderness, but when a bird of this size encounters a power line, the results can be fatal. The San Diego Zoo Safari Park has a program to help train birds to avoid the hazard. Jon Myatt/U.S. Fish and Wildlife Service/Flickr hide caption

itoggle caption Jon Myatt/U.S. Fish and Wildlife Service/Flickr

Professor Douglas Causey logs information as he tags and takes basic measurements of the birds he harvested in the Aleutian Islands on June 4. He is looking at the birds' blood and their diet, hoping to find out the ways the ocean is changing as it warms. Bob Hallinen/ADN hide caption

itoggle caption Bob Hallinen/ADN

Cattle rancher Craig Vejraska pours out feed while checking on his cattle in a smokey field in Cox Meadow, as the Okanogan Complex fires burn outside Omak, Wash., Aug. 26, 2015. Ian C. Bates for NPR hide caption

itoggle caption Ian C. Bates for NPR

Male and female tungara frogs. Among these frogs, the guy with the best call usually wins the gal — except when you throw a third-choice loser into the mix. Alexander T. Baugh/Encyclopedia of Life hide caption

itoggle caption Alexander T. Baugh/Encyclopedia of Life