Photo Gallery: Freshwater Mammals

Hippopotamus

Photograph by Craig Arnold

A Zambian hippo sends an aggressive message by displaying sharp canine teeth that can reach 20 inches (51 centimeters) in length. Bulls use this open-mouthed “gaping” display while standing face to face with one another in order to determine which animal is dominant. Sometimes a show of strength is not enough and the behavior leads to potentially fatal battles. Hippos are dangerous to humans as well.

Manatee

Photograph by Amanda Cotton

Manatees cruise slowly in shallow, warm coastal waters and rivers—like Florida’s gin-clear Crystal River, pictured here. The massive mammals (up to 1,300 pounds or 600 kilograms) are born underwater and never leave the water as long as they live—though they surface to breathe every few minutes. Also known as sea cows, they are insatiable grazers, browsing on a variety of aquatic grasses, weeds, and algae.

Several different manatee species live along the Atlantic coast of the Americas, Africa’s west coast, and the Amazon River.

Muskrat

Photograph by Danny Brown

The muskrat is a common denizen of wetlands, swamps, and ponds, where it dens by tunneling into muddy banks. This large rodent has a body a foot (30 centimeters) long and a flat tail that nearly doubles its length. Muskrats are well adapted for the water and begin swimming at only ten days old. Perhaps best known for their communication skills, muskrats exchange information with one another and warn off predators with their distinctive odor, or musk.

Baikal Seals

Photograph by Sergey Gabdurakhmanov

The world is home to many seals but only one truly freshwater species—the Baikal seal. This seal inhabits the Russian lake of the same name, which is the world’s deepest. Though new generations of Baikal seals are born each year at rookeries like this one, the species does face serious threats. Illegal hunting is an issue, as is widespread pollution from paper and pulp mills and other industry around the lakeshore.

Amazon River Dolphin

Photograph by Kevin Schafer

The charismatic Amazon river dolphin uses echolocation to track down fish and crustaceans in murky river waters. During annual floods the dolphins actually swim through flooded forests to hunt among the trees. Often pink or very pale, the dolphins are relatively easy to spot. The bright hue and the boto's natural curiosity around boats have made the dolphins easy prey for fishermen who target them (illegally) for use as catfish bait. Populations have experienced serious declines in recent years; among traditional Amazonian peoples the boto was long considered a supernatural being that was able to take human form.

Capybara

Photograph by Mark Godfrey

The world’s biggest rodent, the capybara, grows to more than 4 feet (130 centimeters) long and tips the scales at up to 145 pounds (66 kilograms). These water-loving mammals reach such size by grazing on grasses and aquatic plants.

Capybaras are physically well adjusted to their watery environs. They have webbed toes to help them swim well and can dive underwater for five minutes or more. Capybaras are found in Central and South America, populating lakes, rivers, and wetlands from Panama south to Brazil and northern Argentina.

The Nature Conservancy is working with partners to protect habitat for the capybara, including the watery Llanos grasslands. The group is working with local landowners to create private reserves in critical habitat areas and helping bring more resources to a 63,000-acre (25,500-hectare) public protected area in the province of Casanare in northeastern Colombia.

Capybaras

Photograph by Juan Alvarez

The capybara’s eyes, ears, and nostrils are situated high on its head so that it can remain above the surface while the animal swims. The social mammals travel and live in groups dominated by an alpha male and defend their feeding and wallowing territories. Humans hunt (and raise) capybaras for their leather and their meat—which is especially popular during Lent because some South American Catholics consider the animal, like fish, an acceptable alternative to beef or pork.

Beaver

Photograph by Mike Paterson

Beavers are environmental engineers second only to humans in their ability to dramatically reshape the landscape to their liking. Using their powerful jaws and teeth, they fell trees by the dozens to create wood and mud dams, 2 to 10 feet (1 to 3 meters) high and more than 100 feet (30 meters) long. Beaver dams block brooks and streams to flood fields and forest alike. The resulting ponds, which can be enormous, are then graced with a branch-and-mud lodge, which the beavers enter via secure underwater passages.

Beaver

Photograph by Derek Dafoe

Though they are clumsy on land, beavers glide in the water with finlike webbed feet and rudderlike tails, which help them swim along at some 5 miles (8 kilometers) an hour. The mammals also boast a sort of natural wet suit in the form of their oily and water-resistant fur.

Beavers eat aquatic plants, roots, leaves, bark, and twigs. Their teeth grow throughout their lives so wood gnawing is actually necessary to keep them from growing too large and curved. A single beaver gnaws down hundreds of trees each year—typically dropping a 6-inch (15-centimeter) diameter tree in just 15 minutes.

River Otter

Photograph by Lee Streitz

This sleepy river otter also has a playful side. These water-loving mammals seem to take pleasure in sliding and diving and can swim gracefully with their webbed feet and paddlelike tails. Otters have specialized nostrils and ears that close in the water, as well as water-repellent fur. Young otters begin to swim when they are only about two months old. River otters live in burrows by the edge of rivers or lakes in close proximity to the fish they feed on.

Platypus

Photograph by Stephen Babka

The platypus is an improbable mishmash of an animal: It has a furry, otterlike body, a ducklike bill and webbed feet, and a beaverlike paddle tail. Like those other animals platypuses swim well and spend much of their time in the water. Unlike otters or beavers, they lay eggs—one of only two mammals known to do so. Male platypuses also have venomous stingers on their rear feet. These animals burrow near the water’s edge and feed by digging underwater for worms, shellfish, and insects.