Named common seal throughout Europe, this seal frequently observed around
Long Island lives along the shores of eastern Canada, New England and in the
winter, as far south as the Carolinas in a variety of habitats. Their
scientific name loosely means "sea calf" or "sea dog." This latter nickname
is well suited as these seals closely resemble a dog when their head is
viewed at the surface of the water. Harbor seals can be viewed in small
groups hauled out basking on sand bars, rocks or remote beaches, sometimes
popping their heads up in the
waters nearby. Usually wary of humans, they are known to follow fishing
boats, feeding on the scraps thrown overboard and occasionally harbor seals
will haul out on someone's dock or even in their boat.
When hauled out, harbor seals often lie with their heads and hind flippers
elevated in what is often referred to as the "banana-like" position.
When resting in water, harbor seals can be seen in what we call the
"bottling" position, with heads tilted straight back and perpendicular to
the surface; thus assuming the appearance of a floating bottle.
harbor seals generally grow to 5 - 5 ½ feet in length, weighing 200 - 250
pounds, while the smaller females reach approximately 4 ½ to 5 feet,
weighing 150 - 200 pounds. Harbor seals are thought to live to at least 25
years. Males mature at 4 - 6 years, females earlier. Pups, weighing 12 -20
pounds and measuring about 2 ½ feet, are born in the spring. Unlike many
other seal pups, harbor seals are able to swim from birth, although they are
dependent on care and milk from the mother for 3 - 6 weeks before they
venture out on their own. While tending their young, harbor seal mothers are
very protective and will sometimes push the pup beneath the surface or carry
it on her shoulders to avoid danger. Harbor seals
have been shown to dive as deep as 600 meters; their average dive time is 2
minutes and the maximum dive time is 15 minutes (see Costa and Williams.
1999. Marine Mammal Energetics. (figures 5-25 and 5-26) in
Reynolds III, J. E., and S. A. Rommel (eds). 1999.
Biology of marine mammals. Smithsonian Institution Press).
Harbor seals, like most other seal species, migrate southward every
winter, returning to New England and Canada in the summer. On Long Island a
large influx of these seals arrive in November and remain through mid- May,
although some are thought to stay throughout the year.
CRESLI Cupsogue Beach Harbor seal
We've had a total of 13549 harbor seal encounters on 272
trips since 2004. Below are charts of:
Yearly variation in mean # of harbor seals
Monthly variation in mean # of harbor seals per observation
Dr. A. Kopelman has been compiling a catalog of harbor
seals that utilize the haul out site at Cupsogue beach (near
Moriches Inlet). As of September 2016, the catalog
contains 168 seals that are identifiable based upon pelage
marking patterns. Several of these seals have returned
every year, since 2006, other have returned less frequently
but stll return to use that site. The catalog is part of an
on-going long term study of site fidelity and population
dynamics. Samples photos from identified and named seals
can be seen at
The following is excerpted from the December 2012, NOAA Fisheries Stock
Assessment Report for the Western North Atlantic Stock.