It's a bull market for cattle: prices are climbing across the U.S. In Tulsa, Okla., stockyards reported selling 4,500 head of cattle at record prices in a single day's sale last week. Charles Osgood/AP hide caption

itoggle caption Charles Osgood/AP

In the northwestern United States, this crayfish would be just a friendly bit of local fauna. But in Scotland, it's an invasive species wreaking havoc on trout streams. Ari Shapiro/NPR hide caption

itoggle caption Ari Shapiro/NPR

Some researchers have begun to question the notion that dolphins are the super-intelligent creatures they've been made out to be. Pavel Golovkin/AP hide caption

itoggle caption Pavel Golovkin/AP

The rendering industry likes to call itself the world's oldest recycling system. Nearly 100 percent of processed pigs will eventually get used — as meat and in uses as varied as medicine and pet food. iStockphoto hide caption

itoggle caption iStockphoto

A manatee swims underwater in the springs of Crystal River, Fla. — home to a group of residents who have sued the U.S. Fish and Wildlife Service, demanding that the agency consider removing the animals from the endangered species list. Amanda Cotton/iStockphoto hide caption

itoggle caption Amanda Cotton/iStockphoto

The French enjoy horse meat — here's a horse meat butcher in Paris. But even the French were angry that they had been paying beef prices for it last year. Thomas Coex/AFP/Getty Images hide caption

itoggle caption Thomas Coex/AFP/Getty Images

Mammuthus columbi, the Columbian mammoth, used to be common in America, but went extinct about 10,000 years ago. The specimen found south of Dallas is estimated to be 20,000 - 40,000 years old. Illustration by Karen Carr/Perot Museum of Nature and Science hide caption

itoggle caption Illustration by Karen Carr/Perot Museum of Nature and Science