Male harbor seals can weigh between 150–375 pounds and 5-6 feet in length; females range from 100-300 pounds and 4-5 feet in length. Unlike sea otters and river otters, harbor seals don’t rely on fur to stay warm. Instead, their thick layer of blubber provides insulation while storing energy, adding buoyancy in the water and contributing to their streamlined shape. Commonly called “crawling seals”, they use their hind flippers for propulsion underwater only; these flippers can’t be rotated forward and thus can’t be used for locomotion on land. Their front flippers are more versatile – they’re used for steering in the water and along with body undulations, for forward movement on solid ground.
Out and about
In the wild, harbor seals are found in coastal and inland marine waters and estuaries. Because they “haul out” (or come onto land) frequently, they stick to areas where sandbars, beaches or rocks are uncovered at low tide. Harbor seals do not migrate and instead tend to stay in one locale most of their lives and only travel when they’re in search of food or a mate during breeding season. Adult harbor seals are solitary and rarely interact with one another, with one exception: breeding. They are communal during breeding times, with males and females mingling freely.
Harbor seals can dive up to 1,200 feet below the surface and they can remain underwater for close to 30 minutes while hunting for food, although most dives last 3-10 minutes. Their nostrils remain closed most of the time which is handy for an animal that lives in the water – and, once the seals are back above water, they must consciously open their nostrils to resume breathing.
Harbor seals can sleep on land or take naps just below the surface of the water. When snoozing underwater, they come up to breathe every 5-10 minutes, without completely waking up!
More than meets the eye
Harbor seals are a familiar sight in the Puget Sound region. Their heads pop out of the water while we walk along the shore, cross the Sound by ferry, or sit in a waterfront restaurant. Charming and playful, harbor seals captivate us with their gentle eyes, droopy whiskers and round bodies. Beyond their beguiling appearance, they are also barometers of the health of Puget Sound and sentinels of the well-being of the habitats in which they live. The reason for this is found in their diet: harbor seals eat sole, flounder, sculpin, cod, herring, octopus and squid – all links in a food chain that is increasingly vulnerable to pollution, development and other human activities.