Northern Hemisphere in Atlantic and Pacific Oceans
Class Mammalia (mammals), Order Carnivora (carnivores), Family Phocidae (earless seals)
Harbor seals are members of the true seal or “earless seal” family. Their coats are spotted and a variety of colors, including white, gray, brown and black. Male harbor seals grow to an average length of 5.6 feet (1.7 m) and average weight of 265 pounds (120 kg). Females are smaller than males, growing to an average length of 4.5 feet (1.4 m) and average weight of 220 pounds (100 kg).2
Like other true seals, harbor seals do not have external ears and cannot use their hind flippers to move on land. Instead, these pinnipeds “bounce” in a caterpillar-like motion. Harbor seals are have long been considered non-migratory and tend to stay close to home, but telemetry data have shown they sometimes travel 62 to 249 miles from their tagging location. They haul out to molt, give birth, raise their pups, bask in sunlight and avoid predators.
In water, harbor seals are much more graceful. They can spend several days at sea foraging for food and even sleep underwater for up to 30 minutes at a time. Harbor seals hunt in shallow and benthic waters, eating mainly fish, crustaceans, cephalopods and shellfish.3 They typically hunt alone in waters less than 330 feet (100 m), but have been observed diving as deep as 1,575 feet (480 m). Depending on their location, harbor seals are preyed on by great white sharks, Greenland sharks, orcas, Steller sea lions and walruses. If they avoid predators, harbor seals can live for 30 to 35 years.1
Reproduction between harbor seals usually occurs underwater and is not well documented. Females give birth to a single pup every year. Pups can swim immediately after birth and nurse with their mothers for about six weeks. After the nursing period, mothers abandon their pups and mate again while their young typically travel to a new area.2
Historically, harbor seals were hunted in the U.S. because they were viewed as a threat to local fisheries. In 1960, this hunting program ended, but harbor seals continue to face several threats from the humans. Industrial and agricultural pollutant runoff cause some harbor seal populations to experience reproductive problems, disease and vitamin deficiencies.1 Harbor seals are also susceptible to becoming bycatch and suffering starvation due to overfishing. Oil spills, fishing gear entanglement, noise pollution, habitat destruction and harassment from humans also impact harbor seal populations. The Marine Mammal Protection Act of 1972 made it illegal to hunt or harass harbor seals, which includes feeding them and getting too close to them.3 Although they are vulnerable to various threats in their environments, harbor seal populations are considered very stable and are listed as least concern by the IUCN.1
Fun Facts About Harbor Seals
1. Harbor seals can be found in freshwater rivers and lakes, as well as marine waters.
2. There are 5 subscpecies of harbor seals: Eastern Pacific harbor seals; Western Pacific harbor seals; Eastern Atlantic harbor seals; Western Atlantic harbor seals; and Seal Lake harbor seals.1
3. Harbor seal pups can dive for up to 2 minutes once they are only 2 to 3 days old.3
4. Harbor seals are considered the least vocal of all pinnipeds. Unlike their California sea lion neighbors that bark loudly, harbor seals rarely make noise except when disturbed by another being in their personal space.
5. Harbor seals grow to a maximum length of 6.6 feet (2 m) and weight of 375 pounds (170 kg).
6. Harbor seals eat 5 to 6 percent of their weight in food every day.
7. Harbor seals spend up to 85 percent of their day foraging for food.2
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