Across Washington State, hydroelectric dams are blocking salmon as they migrate to their spawning grounds. Enter the salmon cannon. Ingrid Taylar/Flickr hide caption

itoggle caption Ingrid Taylar/Flickr

A great white shark swims near Guadalupe Island off the coast of Mexico in a promotional image for Discovery Channel's Shark Week in 2013. The network special Megalodon: The Monster Shark Lives opened Discovery's annual Shark Week programming in 2013. Andrew Brandy Casagrande/Discovery Channel/AP hide caption

itoggle caption Andrew Brandy Casagrande/Discovery Channel/AP

Trainer Jimmy McConnell of Shelbyville, Tenn., rides champion walking horse Watch It Now before a 2009 football game in Knoxville, Tenn. Celebrations of the breed's distinctive gait are a 75-year-old tradition, but animal rights activists say that for many of those decades, the walking horse industry has abused animals to get their knees even higher. Wade Payne/AP hide caption

itoggle caption Wade Payne/AP

New Yorkers can take city-run classes to learn how to make their homes and businesses less attractive to these guys. Ludovic Bertron/Flickr hide caption

itoggle caption Ludovic Bertron/Flickr

Big brown bats like this one are relatively common in urban areas, sometimes roosting in buildings. Contrary to popular belief, bats rarely carry rabies and are not rodents. They belong to the order Chiroptera, which means "hand-wing." Courtesy of Robert Marquis hide caption

itoggle caption Courtesy of Robert Marquis

Researchers raised two groups of walking, air-breathing Polypterus senegalus — one on land and one on the water. They discovered that each group was able to adapt to be best suited to its environment. A. Morin, E.M. Standen, T.Y. Du, H. Larsson/McGill University hide caption

itoggle caption A. Morin, E.M. Standen, T.Y. Du, H. Larsson/McGill University