Mammals

From whales and dolphins to seals and sea otters. Marine mammals are defined by their reliance on the ocean for food, along with mammalian characteristics such as hair and mammary glands. 

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Sirenians , or seacows, are a group of marine mammals that include manatees and dugongs. In the modern ocean, only one species of seacow is found in each world region, however, the fossil record...
John Hildebrand discusses his research at the Scripps Whale Acoustic Lab on the...
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Many people love seals and sea lions, and it's easy to see why: they’re playful...
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Humpback whales ( Megaptera novaengliae ) are the most abundant baleen whale in...

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Lying on the ice with a few friends is not an unusual way to spend time for walruses, who tend to be sociable animals. Their groups can range from tens to thousands. Each individual herd has a dominant male who is established by...
Bottlenose dolphins ( Tursiops truncatus ) are very social animals, and...
The North Atlantic right whale is one of the world's largest animals, but...

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Stretching up to 16.8 meters (55 feet) long and weighing up to 62 tons (70 tons), the North Atlantic right whale is one of...
A drawing of Phoenix from the Right Whale Catalog documents her callosity pattern and other identifying marks. More about whales can be found in our Tale of a whale featured story .
A North Atlantic right whale with a deep wound caused by entanglement in fishing gear floats at the surface in the Bay of Fundy on August 1, 1999. Crew members on the International Fund for Animal...
“At night, spotted dolphins move offshore into the Gulf Stream’s deep waters in search of squid.” -- Nature's Best photographer, Andrew Sallmon. See more beautiful ocean photos in our slideshow of...
The fringed baleen plates are easy to observe as this North Atlantic right whale skims the water’s surface while it feeds. Many baleen whales suck in as much water was possible, and then push it out...
Polar bear siblings in the Churchill Wildlife Management Area near Hudson Bay spar playfully during migration.
Nick Pyenson, the curator of fossil marine mammals at the Smithsonian's National Museum of Natural History, points to the skull and skeleton of a fossil "toothed" mysticete ( baleen whale ) on the...
"A juvenile California sea lion performing close to the camera. The speed and elegance of these creatures is really unmatched in the oceans," wrote David Henshaw of his image , a winning selection in...
Male northern elephant seals face off on the beach by vocalizing through their extended noses, called proboscises. Every winter, when the seals return to the beach where they were born to breed,...
A harp seal ( Phoca groenlandica ) pup rests on the ice at sunset in the Gulf of St. Lawrence, Canada while its mother hunts. Adult harp seals have dappled gray fur, but the babies are born white and...
“I took this photograph of spinner dolphins in calm waters off the Ogasawara Islands, an archipelago in the Pacific Ocean about 600 miles south of Tokyo.When the sun briefly broke through the clouds...
This magnified photo provides a close-up look at copepods—tiny crustaceans that right whales feed on. There are many species of copepods that live throughout the water column, from floating at the...
In the late 1990's, researchers at the Woods Hole Oceanographic Institution (WHOI) invented the D-Tag —a radio device that can be attached by suction cups to a whale's back. Using a tiny underwater...
My graduate student Jorge and I are departing today for Panama, to excavate a fossil whale that was discovered by an undergraduate student working with Smithsonian Tropical Research Institute...
A fossil vertebra that a Smithsonian researcher's mother found while prospecting in the Gatun Formation. It's not just any vertebra, it belongs to a fossil sea cow! According to Jorge Valez-Juarbe, a...
Phoenix rises out of the waters east of Cape Cod, MA, in April 2003. The rough patches of skin (known as callosities) occur in unique patterns on all North Atlantic right whales and help researchers...
There were fewer than 450 North Atlantic right whales in 2006. Yet it has been illegal to hunt them since 1935. Why haven’t populations increased? Traits that made right whales easy to hunt make them...
An early scale model of North Atlantic right whale Phoenix indicates the location of scars on her tail from entanglements with fishing gear. More about the right whale can be found in our Tale of a...
The North Atlantic right whale is one of the world's largest animals, but scientists estimate that fewer than 450 remain. In the past, they were hunted for their oil and baleen; now they get tangled...
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