Crabeater Seal

## Description

The crabeater seal (Lobodon carcinophaga ), also known as the krill-eater seal, is a true seal with a circumpolar distribution around the coast of Antarctica. They are medium- to large-sized (over 2 m in length), relatively slender and pale-colored, found primarily on the free-floating pack ice that extends seasonally out from the Antarctic coast, which they use as a platform for resting, mating, social aggregation and accessing their prey. They are by far the most abundant seal species in the world. While population estimates are uncertain, there are at least 7 million and possibly as many as 75 million individuals. This success of this species is due to its specialized predation on the abundant Antarctic krill of the Southern Ocean, for which it has uniquely adapted, sieve-like tooth structure. Indeed, its scientific name, translated as "lobe-toothed (lobodon ) crab eater (carcinophaga )", refers specifically to the finely lobed teeth adapted to filtering their small crustacean prey. Despite its name, crabeater seals do not eat crabs. As well as being an important krill predator, the crabeater seal's pups are an important component of the diet of leopard seals (Hydrurga leptonyx ), which are responsible for 80% of all crabeater pups deaths.

## Appearance

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.

## Distribution

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.

## Behavior

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.

## Diet

The Crabeater seals are carnivores and their diet is 89% Antarctic krill. It probably eats other invertebrates as well.

## Reproduction

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.

## Population

### Population threats

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.

### Population number

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.

### Ecological niche

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.

## Fun Facts for Kids

The Crabeater seal spends 8-10 hours feeding, diving more than 100 times.

The teeth of Crabeater seals are designed for the efficient eating of krill. Their teeth have many little points, which filter krill from the water.

Crabeater seals molt, to become brown or gray. The color fades by the end of summer and they turn white.

Crabeater seals travel great distances inland. In December (summer in Antarctica) on the Crevasse Valley Glacier a male pup was found, 113 km from open water, 920 meters above sea level.

When threatened, a Crabeater seal will snort, hiss, show its teeth, and roll over many times, which is probably a tactic evolved to evade Leopard seals and Killer whales.