The Baltic grey seal is a distinct population, separated from the two, considerably larger, populations of Atlantic grey seals.
The grey seal is the biggest seal species in Sweden. An adult male can weigh just over 300 kg and a female weighs approximately 150 kg.
The Baltic grey seals prefer archipelagos and rocky shores. They are social animals and a male often has multiple females. In February–March the females give birth on the ice. The female stays with the pup for three weeks, after which she returns to the males for mating and the pup is left to fend for itself.
The grey seal eats various species of fish. It often stays near river mouths and hunt migrating salmon.
Approximately 35–40 years.
Despite becoming legally protected in 1974, the grey seal population continued to decline due to high levels of environmental toxins in the Baltic Sea. Half of all adult females were estimated to have deformations on the uterus, rendering them infertile. Today, the situation has greatly improved: the concentration of toxins has decreased and the seal population is increasing.
The gestation period is 11.5 months with delayed implantation. When the pup is born it has a white fur, which lacks the water-repelling ability needed for a life at sea. However, it only takes about 3 weeks before more appropriate fur has grown.
20 minutes is the time a grey seal can stay under water without breathing.
A newborn pup weighs 10 kg but will increase to 60 kg in only 4-6 weeks. This is due to the extremely fatty milk.