10 Facts About Seals

Curious Pinnipeds - Some With Ears, Some Without

With their expressive eyes, furry appearance and natural curiosity, seals have a wide appeal. Seals are divided into two families, the Phocidae, the earless or ‘true’ seals (e.g., harbor or common seals), and the Otariidae, the eared seals (e.g., fur seals and sea lions). This article contains facts about both earless and eared seals.

Seals Are Carnivores

Harbor seal (Phoca vitulina) swimming, close-up
Eastcott Momatiuk/The Image Bank/Getty Images

Seals are in the order Carnivora and suborder Pinnipedia, along with sea lions and walruses. “Pinnipedia” means “fin foot” or “winged foot” in Latin. Seals are divided into two families, the Phocidae, the earless or ‘true’ seals (e.g., harbor or common seals), and the Otariidae, the eared seals (e.g., fur seals and sea lions).

Seals Evolved From Land Animals

Baby Galapagos sea lion
Baby Galapagos sea lion. Rebecca Yale/Moment/Getty Images

Seals are thought to have evolved from bear- or otter-like ancestors who lived on land.

Seals Are Mammals

Two seals on a beach
John Dickson/Moment/Getty Images

Seals do spend lots of time in the water, but they breed, give birth to live young, and nurse their young on shore.

There Are Many Kinds of Seals

Southern elephant sea
Southern elephant seal.

NOAA NMFS SWFSC Antarctic Marine Living Resources (AMLR) Program/Flickr/CC BY 2.0

There are 32 species of seals. The largest is the southern elephant seal, which can grow up to about 13 feet in length and more than 2 tons in weight. The smallest species is the Galapagos fur seal, which grows to up to about 4 feet long and 65 pounds.

Seals Are Distributed Throughout the World

Harbor seal
Harbor seal at Nantucket National Wildlife Refuge, MA.

Amanda Boyd/ U.S. Fish and Wildlife Service

Seals are found from polar to tropical waters. In the U.S., the most well-known (and watched) concentrations of seals are in California and New England.

Seals Insulate Themselves Using a Thick Fur Coat and Layer of Blubber

Resting bearded seal
Raffi Maghdessian/Getty Images

Seals are insulated from cold water by their fur coat and by a thick layer of blubber. In polar environments, seals restrict blood flow to their skin surface to keep from releasing internal body heat to the ice. In warm environments, the reverse is true. Blood is sent toward the extremities, allowing heat to release into the environment and letting the seal cool its internal temperature.

Seals Detect Prey With Their Whiskers

California sea lion
California sea lion (Zalophus californianus) in Morro Bay, California.

Mike Baird/Flickr/CC BY 2.0

The diet of seals is varied depending on the species, but most eat primarily fish and squid. Seals find prey by detecting prey vibrations using their whiskers (vibrissae). 

Seals Can Dive Deep Underwater and for Extended Periods

A bearded seal swimming and pup on an ice floe
Jami Tarris/The Image Bank/Getty Images

Seals can dive deeply and for extended periods (up to 2 hours for some species) because they have a higher concentration of hemoglobin in their blood and their large amounts of myoglobin in their muscles (both hemoglobin and myoglobin are oxygen-carrying compounds). Therefore, when diving or swimming, they can store oxygen in their blood and muscles and dive for longer periods than we can. Like cetaceans, they conserve oxygen when diving by restricting blood flow to only vital organs and slowing their heart rates by about 50-80%. In a study of northern elephant seals, the seal’s heart rate went from about 112 beats per minute at rest to 20-50 beats per minute when diving.

Seals Have Several Natural Predators

Orcas swimming underwater

Mike Korostelev/Moment/Getty Images

Natural predators of seals include sharks, orcas (killer whale), and polar bears.

Humans Are the Greatest Threat to Seals

Monk Seal
A Hawaiian monk seal rests on Ke'e Beach, located on Kaua'i.

thievingjoker/Flickr/CC BY-SA 2.0

Seals have long been commercially hunted for their pelts, meat, and blubber. The Caribbean monk seal was hunted to extinction, with the last record reported in 1952. Today, all pinnipeds are protected by the Marine Mammal Protection Act (MMPA) in the U.S. and there are several species protected under the Endangered Species Act (e.g., Steller sea lion, Hawaiian monk seal.) Other human threats to seals include pollution (e.g., oil spills, industrial pollutants, and competition for prey with humans.