Crabeater seals are considered to be the most abundant seals in the world. It is believed by some scientists that there are more of them than all the other seal species combined. Crabeater seals are a "true" or "earless" seal and perfectly adapted to living in Antarctica, almost exclusively amidst the pack ice. They are faster than most "true" seals and can travel faster over ice than a person can run. Ironically, these seals do not, in fact, eat crabs (Antarctic waters have no crabs), but they eat more krill than any other animal. It was the early Antarctic sealers and whalers who misnamed this species, which might more accurately be named the "krilleater seal”. This seal’s abundance is largely a result of the slaughter in Antarctic whales of baleen whales, which made krill more available for seals and penguins.
Crabeater seals live throughout the Antarctic region. They are found mainly on the pack ice and in the near freezing water off the coasts of Antarctica, but some travel as far New Zealand, Tasmania, Australia, South America, and South Africa.
Crabeater seals spend most of their time alone or in a small group. Much larger groups, however, sometimes with as many as about 1,000 individuals, have been seen hauling out on ice floes, particularly during the annual molt, which takes place in January and February. Up to 500 in a herd have been seen swimming and diving together. In spring, juvenile and mature seals will segregate, the juveniles forming large groups on land while the mature ones stay on the pack ice during the breeding season. This species feeds mostly at night, diving fairly deeply in search of prey. During the day they rest on ice floes. These seals are extremely agile on land and sometimes are found far inland, juveniles sometimes accidentally traveling towards the interior of Antarctica. It is assumed that they migrate during the Antarctic winter in search of food but their patterns of movement are unknown.
Crabeater seals are monogamous, which means that one male mates only with one female. The breeding season is fairly short, occurring from October to December. Gestation lasts about 11 months, probably due to delayed implantation. A single pup is born between September and November in the following year, with most births occurring around mid-October. A male usually joins the female just before birth takes place, and protects her and her newborn from other males and from predators. The pup stays close by its mother until weaning takes place, which usually three to four weeks after birth. Young are almost fully grown at two years old, although they do not reach maturity until three to six years old.
There are no major threats facing the Crabeater seal at present. However, development of a large krill fishery could effect its population and the entire Antarctic ecosystem if harvesting on a large scale becomes established. Disease, primarily canine distemper virus, is a threat to Antarctic seal populations, and if outbreaks occur, it can cause mass die-offs. This risk may increase as there is more tourism in the region, and as climate change has more of an impact, though the latter is currently poorly understood. However, initial studies suggest that the number of Crabeater seals may decline as temperatures increase and pack ice is reduced, which is an important habitat for breeding, resting and avoiding predators. Changes in sea ice may also affect access to the Crabeater seal’s preferred foraging areas.
This species is widespread, but the NOAA Fisheries resource states that there is currently no reliable approximate number of Crabeater seals. Currently, an international group of scientists is collaborating to provide a good estimate. The IUCN Red List records the total Crabeater seal population as 8,000,000, including 4,000,000 adults for the area surveyed, with major areas of pack ice around Antarctica unsurveyed. Currently this species is classified as Least Concern (LC) on the IUCN Red List.
The Crabeater seal is an important krill predator, they may also affect leopard seals populations, as items of prey - consume about 80% of all crabeater pups.