Slow to build, these structures can live for thousands of years. The blue whale is thought to be the largest known animal ever to have lived on sea or land. Individuals can reach more than 110 feet and weigh nearly 200 tons. Otters do not have blubber and must rely on dense fur, frequent grooming, much activity, and a voracious appetite to keep them warm in icy water. Sea otters are also a keystone species in coastal kelp forest ecosystems.
Shorebirds are among the world's greatest migrants.
Nearly two-thirds of the species that breed in arctic North America winter in Central and South America. Extremely dependent upon estuaries, mudflats and the sheltered beaches of significant bays, approximately 135 species of shorebirds move through and inhabit North America. Alaska's Copper River Delta, Washington's Gray's Harbor, and the New Jersey and Delaware beaches of Delaware Bay are critical shorebird staging and feeding areas. Sometimes, pods join together to form temporary herds of up to several hundred individuals. Dolphins coordinate this social behavior by communicating through squeaks, grunts, trills, and moans.