by Sharon Young

When most people think of marine mammals, they picture large animals living peacefully in a vast ocean. Few people think of whales, seals, or manatees living near coastal cities and developed areas. But you might be surprised at the many urban environments to which these animals have adapted. Indeed, because of heavy development along the coasts, some marine mammals spend their lives in the middle of intense human activity.

Many "urban whales" are dolphins and porpoises. Taxonomically, dolphins and porpoises are whales—odontocetes, or toothed whales. While scientists still debate about the classification of species and subspecies, there are at least six species of porpoises, 26 species of oceanic dolphins, and five species of river dolphins. Porpoises are regular springtime visitors to Boston Harbor in Massachusetts, where they feed on small prey fish as freighters tower above them and commuter and pleasure boats zip past. Indo-Pacific humpbacked dolphins live amid the busy boat traffic in the shallow coastal waters of Hong Kong and Southeast Asia. Indus and Ganges River dolphins share waterways crowded by the growing human populations of India and Pakistan.

One of the best examples of marine mammals co-existing peacefully with humans are the California sea lions of San Francisco's Pier 39. In 1989, sea lions began using the docks at this city pier as a resting area. No one knows why they came to prefer this urban location over a more secluded spot where they had historically been observed. The pier's sea lion population fluctuates from a few hundred to more than 1,000 in late summer and fall. Although the sea lions were initially viewed as a nuisance, the pier's management decided to surrender the space and officially closed the docks to people. Pier 39 now ranks as one of the city's top tourist attractions.

Some encounters between marine mammals and humans, however, do not have such happy endings. The endangered West Indian or Florida manatee, another gentle marine mammal, is at risk because of its close cohabitation with humans. Found in the shallow waters off Florida's coast, manatees face extinction because of human activity. Boats pose the worst danger—collisions killed 81 manatees last year, and only about 3,200 of these mammals are left. Habitat loss from coastal development is also a serious threat.

Whenever marine mammals live in urban environments, they are at considerable risk from chemical pollution, litter, and carelessly disposed fishing gear. Boats and their propellers are dangers, too. Bottlenose dolphins frolic in the waters just off the beaches from New Jersey to Florida, sharing these coastal waters with human residents and tourists drawn to the sunny shores and to the promise of good fishing. In these areas, dolphins often become entangled in fishing nets set close to the beach and are vulnerable to collisions with fast-moving pleasure and sport-fishing boats.

Wild dolphins are also placed at risk by well-intentioned humans who feed them. Many of us have seen these charismatic animals hand-fed at marine parks and zoos and in movies or on television. So when we see dolphins in the wild, we may feel an urge to feed them ourselves—which can be risky at best and deadly at worst. We must remember that wild animals are exactly that: wild.

At Monkey Mia, a beach on the west coast of Australia where dolphins have received human handouts for nearly 30 years, scientists have noticed that the calves of female dolphins regularly fed by people have a much higher death rate. And dolphins who learn to approach boats for food become more vulnerable to entanglement in fishing nets or even oblivious to the dangers that boats can pose during such close encounters. In fact, feeding wild marine mammals in the United States is illegal under the Marine Mammal Protection Act.

It's exciting to have whales and other marine mammals as neighbors, but it's essential that their natural habitat remain as unpolluted and undisturbed as possible. As naturalist Henry David Thoreau noted, "in wildness is the preservation of the world."

Sharon Young is field director of The HSUS Marine Issues.