The world's rarest seal learned to hide its pups in sea caves
Mediterranean monk seals once lounged and gave birth on open beaches from the Black Sea to the Azores. Hunted, netted and crowded out, the survivors retreated into remote caves with underwater entrances. Only about 800 to 1,000 remain, making them probably the rarest seal, sea lion or walrus species on Earth.
Adults average about 2.4 metres long and roughly 300 kilograms, and may live to 45. They are thought to have the shortest hair of any pinniped, black in males and brown to dark grey in females. Pups arrive about a metre long in dark woolly coats with a white belly patch, usually rectangular in females and butterfly-shaped in males. Hunting by day, the seals eat up to 3 kilograms of octopus, squid, fish and lobster daily, diving as deep as 250 metres, and some have been seen lifting rock slabs to reach prey.
Decline had many causes: commercial hunting in Roman and medieval times, fishermen in the twentieth century killing seals that raided their nets, and spreading coastal development and pollution. The cave refuge is a recent adaptation to human disturbance, and a risky one, since storm surges flooding the caves kill many newborns. Only about 29 percent of pups born between September and January survive.
Two strongholds remain, at opposite ends of the range, so animals cannot move between them. One is the Aegean, with 250 to 300 seals in Greece, concentrated around the island of Gyaros, and some 100 in Turkey. The other is Cabo Blanco on the Atlantic coast straddling Mauritania and Western Sahara, the only site still holding a true colony. In the summer of 1997 more than 200 seals there, two-thirds of the group, died within two months, probably from a toxic algal bloom, though a virus has also been blamed.
Recovery has been slow but real. A few Cabo Blanco seals began using open beaches again, and in 2009 a female gave birth on the sand for the first time in centuries. A Spanish-funded recovery plan helped the colony return to about 300 animals by 2016, when a record 83 pups were born. The last Black Sea sighting was in 1997.
Source: Mediterranean monk seal
