Known to Māori as ihupuku or ihu koropuka, the southern elephant seal (Mirounga leonina) feeds mainly on fish, squid and crustaceans, which they catch by diving to great depths. Adult males are identifiable by their large inflatable noses.
These seals breed mainly on subantarctic islands and the Argentine coast, especially at Península Valdés. Within New Zealand’s territorial waters, the main breeding sites are Campbell Island and the Antipodes Islands, although isolated pupping occurs along the Otago coastline. Pups are usually born between September and October, and the mothers leave them after just three weeks. Females start breeding at about 4 years.
The maximum recorded age is 20 years, but the usual life span is 18 years for males and 10–13 years for females.
Natural selection for size
At up to 3,700 kilograms of quivering blubber, the male southern elephant seal is the world’s largest seal. There is intense competition for the sections of beach on which the females breed, and the adult males seem to regard fighting as just another form of communication. Consequently only a few, larger males mate with the females. This has produced strong selection for the characteristic most likely to ensure success: size.
Males can be up to 10 times heavier than females, which often weigh less than 400 kilograms (although at sites like South Georgia, near the Antarctic Peninsula, they may weigh up to 900 kilograms).