On a gray morning off New England, notice the head first. A harbor seal has the face of a wet dog. A grey seal has the profile of a horse: a long, straight muzzle running off the brow without a dip, on a body built to a different scale entirely. This is the largest seal of the US Atlantic coast, and once you learn the silhouette, you won’t confuse the two again.
The horse head, and what comes behind it
Adult grey seals carry a long, convex muzzle, especially the bulls, whose Roman nose thickens with age. The nostrils sit nearly parallel, where a harbor seal’s form a V. Coat pattern flips with sex: males run dark with pale blotches, females and juveniles run silver-gray with dark ones. Size is the other tell. Cows commonly stretch around two meters, and big bulls go well past that. A mature cow weighs a couple of hundred kilograms, while a full-grown bull can top three hundred. Any seal that dwarfs the harbor seals beside it, with that long straight profile, is a grey seal.
An Atlantic seal with a New England core
Grey seals live on both sides of the North Atlantic. On the American side, the range runs from Maine south along New England and the mid-Atlantic, with wandering animals reaching the Carolinas. The population centers north: ledges, sandbars, and islands in the Gulf of Maine and off Massachusetts hold seals through the year, and animals disperse south mostly in winter. Muskeget Island, off Nantucket, is the country’s principal pupping colony, and seals have recolonized islands off Maine and Cape Cod in force.
Fish on the bottom, squid in the dark
Fish makes up the bulk of the diet, around four parts in five: sand lance, herring, flatfish, cod, and skates, with squid, octopus, and crustaceans filling the rest. Grey seals forage mostly along the bottom, reading prey with their whiskers in water too murky for eyes. Typical dives run a few minutes, but they can stay down far longer when the hunting demands it. Haul-outs come at any hour, while feeding runs peak toward dawn and dusk, and a seal may work offshore for days between rests on the ledges.
White coats on winter islands
In the US, pups arrive in the depths of winter, mostly December through February. Each mother bears a single pup, born in a creamy white coat that inspired old sailors’ tales of ghosts on the rocks. The milk is among the richest of any mammal’s, and the pup balloons on it, packing on blubber until weaning ends the arrangement at barely three weeks. The mother then returns to sea, mates, and leaves the pup to fast, shed its white coat, and teach itself to fish.
The calendar after that is finely staged. The embryo pauses development for months before implanting, so the active pregnancy runs about eight months while the gap between breeding and birth spans most of a year. One pup a year is the rhythm. Females mature at roughly four years old and males near five, though a bull rarely holds breeding ground until much older. Grey seals are long-lived for seals, females especially, with records past forty years.
A recovery with teeth in it
A century ago, New England paid bounties on grey seals, and the US population hovered near zero. Federal protection in 1972 changed the trajectory, and the rebound since has been one of the Atlantic’s quiet wildlife successes, with thousands of pups now born each year in American waters. Globally the species numbers several hundred thousand and sits at Least Concern. Recovery has brought friction. Seals steal fish from gear and draw complaints from fishing towns. Sharks, especially white sharks, have followed the seals back to Cape Cod’s beaches. And the seal’s own charisma creates its own problem: a hauled-out seal is resting, not stranded, and a lone pup on a winter beach is usually waiting for a mother fishing offshore.
