This young whooping crane is on its first fall migration, guided by an Operation Migration ultralight aircraft. Each whooper in this population wears an identification band, and many carry tracking devices that record their movements in detail. Joe Duff/Operation Migration USA Inc. hide caption

itoggle caption Joe Duff/Operation Migration USA Inc.

Piglets in a pen on a hog farm in Frankenstein, Mo. Jeff Roberson/AP hide caption

itoggle caption Jeff Roberson/AP

The underlying biology of age-related memory glitches — in old mice and old people — is different from what happens with Alzheimer's, recent research suggests. Anthony Bradshaw/iStockphoto.com hide caption

itoggle caption Anthony Bradshaw/iStockphoto.com

Marine biologist Stefano Piraino thinks overfishing is one of the reasons jellyfish populations are growing. He said if you take fish out of the oceans, it leaves more food for jellyfish. The jellyfish here are known as Pelagia noctiluca, the mauve stinger. Courtesy of Stefano Piraino/MED-JELLYRISK hide caption

itoggle caption Courtesy of Stefano Piraino/MED-JELLYRISK

In this image from video provided by the Smithsonian National Zoo, Mei Xiang gives birth to a cub two hours after her water broke Friday. A second cub born Saturday was stillborn. AP hide caption

itoggle caption AP