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Marine Mammals

Marine mammals are warm-blooded vertebrates (animals with a backbone) that bear live young and nourish them with milk as land mammals do, but that spend most or all of their lives in the ocean. They are broken into three groups that share similar adaptations to their aquatic life, but that have very different origins and life patterns.

Sirenians, the manatees and dugongs, are slow plant feeders found in warm, shallow coastal habitats. Pinnipeds, the seals, sea lions and walruses, bear young on land, but spend most of their time in the ocean. Cetaceans, the dolphins, porpoises and whales that spend all of their lives in the ocean, include both toothed species that are carnivorous predators, and filter-feeding baleen whales that consume huge quantities of tiny plankton. In size, marine mammals range from small seals and porpoises to the largest animal that has ever lived, the blue whale. Many cetaceans and pinnipeds dive to remarkable depths to feed, feats only recently discovered using digital tags that record the animals' movements, direction, and depth over time.

Marine mammals play important ecological roles as both predator (many hunt for fish) and as prey, both for sharks and other, larger marine mammals. Humans have also long hunted marine mammals for food and fur. Although hunting pressures have declined, marine mammals still suffer from low numbers and inadvertent human activities such as certain fishing methods, boating and shipping traffic, and increasing ocean noise.

WHOI scientists have conducted marine mammal research for decades, from making the first underwater recordings of marine mammal sounds in the 1940s, to the development of digital tracking tags and CT scanning methods. The WHOI Marine Mammal Center (MMC), fosters research on whales, dolphins, and seals, including their behavior, health, anatomy, and perception; methods to free entangled whales and the causes of strandings; and marine mammal populations' link to ocean conditions and plankton abundance. A particular focus is the endangered north Atlantic right whale, an animal that was hunted nearly to extinction and whose population only includes 300 to 400 individuals.

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News & Insights

Critically Endangered North Atlantic Right Whales Getting Smaller, New Research Finds

A report out this week in Current Biology reveal that critically endangered North Atlantic right whales are up to three feet shorter than 40 years ago. This startling conclusion reinforces what scientists have suspected: even when entanglements do not lead directly to the death of North Atlantic right whales, they can have lasting effects on the imperiled population that may now number less than 400 animals. Further, females that are entangled while nursing produce smaller calves.

Rare Drone video shows critically endangered North Atlantic right whales

May 10, 2021   During a joint research trip on February 28 in Cape Cod Bay, Mass., WHOI whale trauma…

Unicorns of the Arctic face a new potential threat

Narwhals and other marine mammals could be vulnerable to a new threat we’ve become all too familiar with: COVID-19

WHOI working to help save critically endangered North Atlantic right whales

North Atlantic right whales are in crisis. There are approximately 356 individuals remaining, and with over 80% bearing scars of entanglements in fishing line, the race to save this species is more critical than ever.

For Mark Baumgartner, Whale Safe is the natural evolution of WHOI’s work with passive acoustics

Mark Baumgartner is an expert ocean listener who’s research is providing the groundwork for a new system to reduce ship collisions with whales

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News Releases


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WHOI in the News


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From Oceanus Magazine

Harnessing the Power

Can wind developers and ocean scientists work together to get US offshore wind cranking?

Scientists Reveal Secrets of Whales

Researchers have known for decades that whales create elaborate songs. But a new study has revealed a component of whale…

Scientists Reveal Secrets of Whales

Using drones to fly into the misty “blows” of exhaling humpback whales, scientists have found for the first time that…

Eavesdropping on Whales

WHOI scientist Mark Baumgartner has installed a mooring in New York waters that listens for whales and sends back alerts. The prototype advance-warning system could one day help reduce shipping collisions with whales.

How Would ‘On-Call’ Buoys Work?

WHOI engineers are developing a new kind of lobster trap buoy that could help keep whales from getting tangled in fishing gear.…