An aggressive encounter between two male greater prairie chickens (Tympanuchus cupido). During aggressive encounters, males leap into the air and strike their opponent with feet, wings and/or beak. Fort Pierre National Grassland, South Dakota. Gerrit Vyn/gerritvynphoto.com hide caption

itoggle caption Gerrit Vyn/gerritvynphoto.com

A stunning golden tapestry woven from spider silk is unveiled at the American Museum of Natural History in New York City after four years of work — and the help of more than 1 million spiders. R. Mickens/AMNH hide caption

itoggle caption R. Mickens/AMNH

A smallmouth bass caught on a lake near Ely, Minn. One-third of smallmouths surveyed by the USGS showed signs of intersex. Sam Cook hide caption

itoggle caption Sam Cook

A glacier in Patagonia, Argentina, calves, with a sudden collapse of ice. Researchers say that the activity that precedes these types of tipping points and the triggers that cause them may follow predictable patterns. Philip Stanley Dickson/iStockphoto.com hide caption

itoggle caption Philip Stanley Dickson/iStockphoto.com

Julie Feinstein, collection manager of frozen tissue lab at AMNH, removes a rack of samples from one of the liquid nitrogen-cooled storage vats. She's wearing special gloves so that, as she puts it, she doesn't stay attached to the vat. R. Mickens/AMNH hide caption

itoggle caption R. Mickens/AMNH