MAC COMO ZOO
Scientific Name: Phoca vitulina
Distribution: Harbor seals are found in coastal waters in the North Atlantic and Pacific Oceans. They tend to occur above 30ºN in the Atlantic and 28ºN in the Pacific, though vagrants have been found as far south as Florida. Five subspecies have been identified in different regions, including one freshwater subspecies.
Habitat: Harbor seals spend most of their time in the water, and they will forage in a variety of marine habitats, including deep fjords, coastal estuaries, and high-energy rocky coastal areas. They forage at the mouths of freshwater rivers, and sometimes swim several hundred miles upstream. Harbor seals breed and give birth on land, and will haul out on sand or pebble beaches, intertidal rocks, and sometimes ice floes.
Description: Harbor seals tend to be medium sized relative to other pinipeds, males average 63 inches long, females average 58 inches, and harbor seal pups average 32 inches long. Their bodies are spindle shaped, sleek and smooth, allowing them to move quickly through the water. Their flippers are relatively short, and the front flippers have strong claws at their tips. Harbor seals have stout, rounded heads, wide snouts, and distinctive v-shaped nostrils. They are members of the earless seal group, and have no outer ear flap. Harbor seal coloration can vary widely, some seals have light tan or silver fur with scattered dark spots, and others are almost all black with scattered light rings. Darker harbor seals tend to have light coloration on their bellies. Seals living in more southern regions of the Pacific tend to be dark, while seals in the far north of the Pacific Ocean and in the North Atlantic tend to be lighter. Unlike fuzzy white spotted seal pups, young harbor seals tend to have the same coloration as adults
Diet: Harbor seals are carnivorous generalists. They eat small to medium-sized fishes, including cod, mackerel, and herring, as well as octopus, squid, and crustaceans. Shrimp are especially important to young harbor seal pups. Harbor seals will eat many different types of food, but the biggest part of their diets tends to be made up of just a few. Because harbor seals prey on commercially important species, they often come into conflict with fishermen.
Behavior: Harbor seals are solitary mammals, but they do occasionally go to a haul-out space that is shared by other pinnipeds (carnivorous aquatic animals with flippers). The adults rarely interact with each other or with any other species. They usually maintain a space of 1 meter from other each other. If they are touched, they respond aggressively by growling, snorting, flipper-waving, head-butting, or biting. Although, the young harbor seals do interact with each other far away from the adults. Harbor Seals become less playful as they mature.
Harbor seals have a few preferred haul-out spaces, although their current favorite varies with the season. The time and day that they go to the site varies depending upon the individual’s mood. While at the haul-out site, they rarely move to other sites, but they often turn their head to watch for predators.
Breeding: Males are sexually mature at 3 to 7 years of age, about when they reach 165 pounds. Females become sexually mature at about the same age of 3 to 6 years of age, about when they reach 110 pounds. During mating season, sexually mature harbor seals express mating behavior toward others and copulation occurs. The gestation period takes from 9 to 11 months, and most pups are born between February and July. The pups are born either on land, ice, or in water near the shore. Generally, females give birth to one pup per year, but multiple births are possible. The average pups are between 75 to 100 centimeters long and weigh about 18 to 26 pounds. Right after birth, pups are capable of opening their eyes and following their mother.
Adaptations: Harbor seals have many adaptations which make them good at swimming and diving. They also have adaptations which allow for thermoregulation and sleeping in the water. Harbor seals have specialized foreflippers which help them to steer. Their hind flippers can be moved from side to side to move forward. They have the ability to swim forward and upside-down, but they are not as skilled at swimming backwards. Harbor seals can swim as fast as 12mph, which is useful for out swimming predators, but they are usually seen cruising at slower speeds. Although most of the things harbor seals feed upon are found in shallow waters, they have the ability to dive 200 m (656 ft) or more! When a harbor seal is two days old it already has the ability to hold its breath for two minutes. Adult harbor seals can stay underwater for up to thirty minutes. Harbor seals have more blood than similarly sized land mammals. This allows the seal to retain more oxygen and stay submerged longer. Harbor seal muscle contains more of the protein myoglobin, which is used for binding oxygen. This high concentration of myoglobin allows seal muscle to store more oxygen than the muscles of many other mammals. Harbor seals have the ability to sleep on the land or in the water. When sleeping in the water Harbor seals are able to float vertical in the water with only their head exposed. This allows them to breathe while sleeping. Harbor seals have blubber which allows them to retain heat. They typically keep their skin temperature 1°C warmer than the water around them.
Conservation: Many populations of harbor seals have had their populations reduced by human activity. The commercial fishing industry targets many species of fish which are part of the harbor seals’ diet. Some people believe that harbor seals reduce fish population and they hunt harbor seals hoping for fishing booms. However, the marine food web is very complex and try to eliminate a species often has unforeseen effects. In U.S. waters it is illegal to hunt of harass seals because they are protected under the Marine Mammal Protection Act of 1972. However, native subsistence hunting is allowed and seals can be collected for research, education, and public display. It is allow legal to accidentally take in a restricted number of seals during commercial fishing. Many Zoological parks, such as SeaWorld rescue, rehabilitate, and release harbor seals in an attempt to keep populations stable.
MORE ON THE EVOLUTIONARY HISTORY OF THE HARBOR SEAL
Mouchaty, Suzette, Josheph A. Cook, and Gerald F. Shields. "Phylogenetic Analysis of Northern Hair Seals Based on Nucleotide Sequences of the Mitchondrial Cytochrome B Gene." Journal of Mammalogy 76 (1995): 1178-1185. JSTOR. 24 Apr. 2008.
Perrin, W.F., Wursig B., & Thewissen J.G.M (Ed.). (2002). Encyclopedia of marine mammals. San Diego, CA: Academic Press.