Skip to content
For WHOI personnel, vendors, and visitors: COVID-19 Guidelines

Seal Facts

graphics-SIPEX_P_Kimball-IMG_9491_264595_296953.jpg

Seals like this one photographed during the Sea Ice Physics and Ecosystem Experiment (SIPEX-II) in Antarctica, depend on sea ice to survive. They hunt for food, such as fish and krill, under the ice, and use the ice surface for rest and to have their pups. (Photo by Peter Kimball, Woods Hole Oceanographic Institution)

What are they?

  • Seals are pinnipeds, a group of animals with three separate families—phocidae (eared seals), otaridae (non-eared seals), and odobenidae (walruses)—that are the only mammals that feed in the water and breed on land.

Where do they come from?

  • Evidence suggests that pinnipeds evolved from a bear-like land animal that hunted in the water for food.

How many are there?

  • There are more than 30 species of seals worldwide.

What do they eat?

  • Seals are carnivorous and dive underwater to hunt for fish, crustaceans, seabirds, and other marine animals. Whales, sharks, and even other seals are the primary non-human predators of seals.

How deep can they dive?

  • Elephant seals are champion divers—they have been known to reach depths of almost 2,400 meters (more than 7,800 feet) and to remain submerged for 100 minutes.

How do they survive underwater?

  • Seals are protected from the cold by a thick layer of blubber; a clear membrane covers their eyes and their nostrils close and blood circulation to most of their organs is reduced while diving. They also have sensitive whiskers that help them detect prey in murky water.
  • Seals can sleep underwater and can even surface to breathe without waking.

How often do they give birth?

  • A female seal, called a cow, gives birth to one pup about once a year on land. The pups are nursed anywhere between four days and one month.
  • Most mother seals don't eat while nursing, relying instead on blubber stores for nutrition.

How often do they molt?

  • Seals molt, or shed their fur, about once a year (except their first), a process that can take as long as six weeks.

Are they in danger?

  • The Caribbean monk seal was declared extinct in 2008. Other species have been hunted to near-extinction.

Gray Seals

  • Worldwide, gray seals number about 300,000 and are found on both sides of the Atlantic in three distinct populations: Western Atlantic (150,000), Eastern Atlantic (130,000 – 140,000), and Baltic (7,500).
  • Western Atlantic gray seal bulls can reach 2.5–3.3 meters (8.2–11 feet) in length and weigh as much as 400 kilograms (880 pounds); cows are much smaller, typically 1.6–2.0 meters (5.2–6.6 feet) long and 250 kilograms (550 pounds).
  • Gray seals are gregarious animals—they gather in large groups on shore to breed, give birth, and molt.
  • Female gray seals live up to 35 years and males about 25 years.
  • Gray seals primarily hunt squid, fish, and sandeels; their main predators are humans, sharks, and orcas.
  • Gray seal pups are born in autumn (September to November) in the eastern Atlantic and in winter (January to February) in the west, and are born with white fur, which molts after two to four weeks. They nurse for two to three weeks and can quadruple in size during this time because a mother's milk is up to 50 percent fat.
  • One to four weeks after being weaned, the pups disperse and have been known to wander more than 1,000 kilometers (600 miles).
  • The mortality rate for gray seal pups is between 30 and 55 percent, largely due to fishing bycatch, entanglement in fishing gear, pollution, boat strikes, and hunting.
[ ALL ]

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…

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 specialist Michael Moore, National Geographic photographer Brian Skerry, and scientists from New England Aquarium, witnessed a remarkable biological event: North Atlantic right whales in a surface active group, also known as a SAG. SAGs involve…

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

[ ALL ]

News Releases


[ ALL ]

WHOI in the News


[ ALL ]

From Oceanus Magazine

Whale Safe

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

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 songs that has long been overlooked—sort of a booming baseline to go along with the treble. Aboard a small research boat, a research team measured two elements of songs from a group of humpback whales…

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 songs that has long been overlooked-sort of a booming baseline to go along with the treble. Aboard a small research boat, a research team measured two elements of songs from a group of humpback whales…

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…