Seals & Sea Lions

Seals and sea lions belong to a group of marine mammals called pinnipeds, which means fin or flipper-footed. These animals live in the ocean, but are able to come on land for long periods of time. Some species have evolved the ability to hold their breath for up to two hours and dive to depths of more than 6,500 feet when looking for food.

There are two families of pinnipeds: Phocids and Otariids. Phocids are also known as earless seals or “true” seals. They have ear holes, but no external ear flaps. They also have small front flippers and move on land by flopping along on their bellies. At sea, these seals move their rear flippers back and forth like a fish's tail to propel themselves through the water. Phocids include the harbor seal and Hawaiian monk seal.

Otariids, also known as eared seals, include sea lions and fur seals such as the Steller sea lion and the northern fur seal. Unlike true seals, they have external ear flaps. Their front flippers are large, and on land, they are able to bring all four flippers underneath their bodies and walk on them. Otariids propel themselves in the water by paddling their front flippers and using their rear flippers to steer. 

All seals and sea lions are protected under the Marine Mammal Protection Act, and some are also listed under the Endangered Species Act. Together with our partners, we work to study, protect, and conserve these unique marine mammals and their habitats.


Species News

Adult monk seal lying on the sand, eyes open, facing the camera, with a darker-colored pup on its left side, resting on a sandy beach with the ocean visible in the background. The pup’s right foreflipper is extended, touching the mother seal. Monk seal mother and pup on Hōlanikū (Kure Atoll). Credit: NOAA Fisheries/Sarah Glover (Permit #22677, PMNM-2023-001)
food web for Bering Sea fish and other species, graphic showing connections between species This is a path diagram for the Bering Sea and Aleutians Islands marine ecosystem. It shows linkages between ecosystem variables. Arrows correspond to suspected relationships. An arrow pointing from X to Y indicates that a change in X is estimated to cause a change in Y. The number next to each arrow shows the estimated magnitude of the change (red arrows indicate a negative change and blue arrows indicate a positive change).
Brenda Becker sits in the sand on a beach with four seals spaced a distance apart along the water’s edge. Her back is toward the camera, and she is leaning back, appearing to observe the seals through binoculars. Brenda Becker maintains a low profile while photographing monk seals so as not to disturb them. Credit: NOAA Fisheries/Megan Ely (Permit #22677, PMNM-2023-001)
HPAI Testing on a seal. Marine Mammals of Maine take nasal swabs from a harbor seal for HPAI testing. Credit: Marine Mammals of Maine

Research

Cape Shirreff Situation Reports 2023-2024

These reports highlight science activities and events from the U.S. Antarctic Marine Living Resources Program Field Camp at Cape Shirreff, Livingston Island, part of the South Shetland Islands of Antarctica

Peer-Reviewed Research

First Demographic Parameter Estimates for the Mediterranean Monk Seal Population at Madeira, Portugal

We provide the first comprehensive demographic assessment of the Endangered Mediterranean monk seal…

Peer-Reviewed Research

Publications by Northeast Passive Acoustics Branch Staff

We regularly publish their findings in scientific journals and Center-produced documents.

Passive Acoustic Research in the Atlantic Ocean

Marine mammals and many fish produce and receive sound in the ocean. In an environment where vision is limited, hearing is one of the most important senses. These animals rely on sound for navigating, socializing, establishing dominance, attracting…

Viewing Marine Life

Watching marine animals in their natural habitat can be a positive way to promote conservation and respect for animals and their environment.

On Shipwreck Beach on the south coast of Kauai, Hawaii, an endangered Hawaiian monk seal takes a nap on the beach. The sign in the foreground instructs people to walk around the seal.