The Caspian seal is the only mammal living in the world's largest saltwater lake.

Nature · Published 3 October 2026 Swipe more like this →

In short: As the sole mammalian resident of the Caspian Sea, this small earless seal faces a precarious future. Once numbering in the millions, the species has been decimated by hunting, industrial bycatch, and environmental shifts. Today, these unique animals navigate a landscape of shrinking ice and fragmented conservation efforts.

The Caspian seal (Pusa caspica) is a biological outlier, uniquely adapted to the brackish waters of the Caspian Sea. Belonging to the family Phocidae, they are among the smallest pinnipeds, with adults typically weighing about 55 kg. Their evolutionary history is thought to be linked to the ringed seal, which likely migrated from Arctic waters millions of years ago, eventually becoming landlocked as river connections vanished before the major Pleistocene glaciations.

Their life cycle is dictated by the seasonal transformation of their environment. During winter, they congregate on the ice of the northern Caspian to breed and give birth to single pups. As the ice melts in spring, they migrate to the deeper, cooler southern reaches. Unlike their relative, the Baikal seal, which dives to 400 meters, the Caspian seal is a shallow diver, rarely exceeding 50 meters. Their diet is highly seasonal, shifting from sculpins and gobies in the winter to a summer menu dominated by kilka, which can account for nearly 70 percent of their intake.

The species has faced a catastrophic decline, with populations dropping by over 90 percent since the early 1900s. While hunting was the primary driver of this collapse during the 20th century, modern threats are more complex. They include entanglement in sturgeon fishing nets, outbreaks of canine distemper virus, and a shrinking food supply caused by commercial fishing and the invasive comb jellyfish. Classified as endangered by the IUCN since 2016, the seals remain vulnerable because conservation plans across the five bordering nations—Azerbaijan, Iran, Kazakhstan, Russia, and Turkmenistan—are often inconsistent and lack legal enforceability.

Despite these challenges, there are glimmers of hope. Kazakhstan has increased efforts to deter illegal fishing, and coastal communities in Iran have begun rehabilitating injured seals rather than euthanizing them. With an estimated 68,000 adults remaining, the survival of this isolated population depends on whether regional cooperation can overcome the fragmented management that has defined their recent history.

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