Phoca largha
The harbor seal's near-twin, separated by one decision: where to have the baby.
Spotted seals and harbor seals look almost the same, are closely related, and in places such as Bristol Bay in Alaska they share the same water. Even experienced observers mix them up. The reliable difference is not appearance at all. It is behaviour, and specifically where each species gives birth.
Harbor seals pup on land: rocks, sandbars, beaches. Spotted seals pup on drifting sea ice, far offshore over the continental shelf. Biologists think that single difference in breeding habitat is what split the two species in the first place, because two populations that breed in different places at different times stop interbreeding even if they feed side by side the rest of the year.
The spotting does differ if you look closely. A harbor seal's markings tend toward larger blotches and rings, sometimes dark on light and sometimes light on dark. A spotted seal's markings are exactly what the name promises: small, separate, evenly scattered dark spots on a pale silvery ground. It is a subtle call, and it is one reason abundance estimates for this species are so poor.
Most true seals have no family life whatsoever. Males compete, mate and leave. Females raise a pup alone for a few weeks and then abandon it. Spotted seals are the exception. During the breeding season they form what biologists literally call family groups: a female, a male, and her pup, sharing one ice floe.
The male is thought to be annually monogamous, staying with one female for the season, defending the floe and waiting for her to wean the pup, at which point the pair mate. NOAA describes this trio structure as characteristic of the species. Among true seals it is unusual enough to be worth stopping over.
Pups are born from January through April depending on latitude, earliest in the Yellow Sea and latest in the northern Sea of Okhotsk and the Bering Sea. They arrive in white lanugo, nurse for three to six weeks, and more than triple their birth weight in that time. Unlike bearded seal pups, they mostly stay out of the water until they have moulted.
The Bohai Sea, tucked into the coast of northeastern China, freezes just barely every winter. Spotted seals travel there each year, give birth on the thin, temporary ice at the mouth of the Liao River, and leave when it melts.
That population has had a hard century. Hunting, coastal industrial development and pollution cut it from roughly 2,300 animals to about 1,000 over thirty years, and live capture for aquariums added another pressure on top. China now gives the species first-class national protection, runs daily patrols in the bay, and has established protected areas around key haul-out sites. The counts have started climbing again, passing 800 wild seals recorded in Liaodong Bay in 2026.
This population is also the clearest early-warning system in the species. Ice at the extreme southern edge of a range is the first ice to fail as the climate warms, and a seal that needs ice this far south has almost no margin left.
Spotted seals are not deep divers. NOAA describes them as feeding almost entirely over the continental shelf in water less than about 200 metres deep, on a diet dominated by fish with some crustaceans and squid. Pacific herring and crustaceans matter almost everywhere in the range except the central Bering Sea, and walleye pollock is important nearly everywhere except the Chukchi Sea.
Their year is organised around ice. In autumn they move south through the Bering Strait ahead of the advancing ice edge. They winter in Bering Sea pack ice over the shelf, breed and moult there in spring, then head for coastal waters and shorelines for the summer once the ice has gone.
They rarely use dense pack ice, preferring the loose, broken outer fringe where floes are separated by open water. That preference is specific, and it matters. A seal that needs the ragged outer edge of the ice is affected not just by how much ice exists, but by where the edge sits and how long it lasts.
Nobody knows how many spotted seals there are. NOAA says so plainly. The reasons are structural rather than lazy: the animals are spread across the pack ice of two oceans and several countries, they look almost identical to another species, they are hauled out only part of the day, and much of the range sits in Russian and Chinese waters surveyed by different programmes using different methods.
Modern surveys fly aircraft carrying both cameras and thermal infrared sensors, because a warm seal on cold ice is easier to detect as a heat signature than as a shape. The images then have to be classified by species, which drags the harbor seal confusion straight back in, and corrected for the fraction of the population that was underwater and therefore invisible.
The result is a strange pair of answers sitting side by side. The range-wide figure is "more than 500,000, probably", based on old and crude estimates. The local figure is "more than 800 in Liaodong Bay in 2026". Both are real. They just represent completely different amounts of effort applied to completely different amounts of coastline.
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