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Rationale

Due to its widespread occurrence and very large population size, the Crabeater Seal should remain classified by IUCN as Least Concern.

Distribution

The distribution of Crabeater Seals is tied to seasonal fluctuations of the pack ice. They can be found right up to the coast and ice shelves of Antarctica, as far south as the Bay of Whales (Lindsey 1938), during late summer ice break-up. They occur in greatest numbers in the seasonally shifting pack ice surrounding the Antarctic continent. As vagrants they travel as far north as New Zealand and the southern coasts of Africa, Australia and South America. Crabeater Seals have been known to occasionally wander far inland and die in the dry valleys adjacent to McMurdo Sound. A live animal was found 113 km from open water at an elevation of 920 m asl, and carcasses have been found as high as 1,100 m asl (Kooyman 1981, Rice 1998).

Habitat View more ecological information

Population trend

Trend

The Crabeater Seal is a widespread species, and, as is the case for other Seals inhabiting the Antarctic pack ice, population assessments are very difficult and expensive to conduct and therefore infrequently undertaken. Published global population estimates range from two million (Scheffer 1958) up to 50â75 million animals (Erickson et al. 1971). However, early estimates were based on very limited sampling and were highly speculative. The most recent available data, obtained during the multi-national effort conducted under the umbrella of the Antarctic Pack Ice Seal program in the late 1990s, provided a population size estimate of approximately 8,000,000 animals for the area surveyed (Southwell et al. 2012). Considering that major areas of the pack ice around the continent were not surveyed, there is a large uncertainty regarding the actual population size of the species. Yet, Crabeater Seals are considered to be one of the most abundant seal species (if not the most abundant) and one of the most numerous large mammals on Earth.

Threats

There are currently no direct threats from human activity throughout most of the speciesâ normal range.

A mass die-off of Crabeater Seals was reported from an area near a research base on the Antarctic Peninsula in 1955 (Laws and Taylor 1957). About 3,000 animals were trapped in areas five to 25 km from open water and most died over a two to three month period. None of the animals examined appeared to be starving, and numerous abortions of foetuses were noted. A disease outbreak was suspected, but never identified. Antibodies to canine distemper virus were found in Crabeater Seals from this area in 1989 (Bengtson et al. 1991).

The effects of global climate change on Antarctic seals are unknown. Learmonth et al. (2006) suggest that Crabeater Seal numbers may decline with increasing temperatures if Antarctic sea ice is significantly reduced. Loss of sufficient areas of pack ice habitat used for pupping, resting, avoidance of predators, and access to preferred foraging areas because of changes from warming could lead to population declines. The loss of sea ice has the potential to negatively impact Crabeater Seals given their high level of specialization on Antarctic Krill. Sea ice coverage is of particular importance for the survival of juvenile stages of Krill, and ultimately determines the biomass of adult Krill that is available for higher trophic level predators. It is unclear whether Crabeater Seals might be able to switch from their highly specialized, Krill-based diet, to a more generalist strategy with rapid loss of sea ice. The effects of loss of large amounts of ice on the Antarctic continent, general climate warming, or sea level rise, on Antarctic Ocean circulation and productivity and on Antarctic marine resources such as seals are unknown.

Seasonal tourism in the Antarctic and Sub-Antarctic has increased steadily in the last 30 plus years, and is currently at all-time high levels. The effects of increased vessel noise, disturbance from vessel passage, and close approach by people in small boats and on land on Crabeater Seal behaviour, distribution and foraging are unknown. There is a small risk of injury to animals from collision with boats or crushing from large vessel passage through ice fields.

There are no reports of significant interactions between Crabeater Seals and fisheries. Commercial harvest of Krill may pose a threat to Crabeater Seals, if it ever becomes established at a large scale.

Uses and trade

Several brief episodes of commercial harvesting of Crabeaters ended when they were determined to be economically unsuccessful.

Conservation

The Crabeater Seal is not listed as endangered or threatened on any National Red List. Crabeater Seals are protected by the Antarctic Treaty and the Convention for the Conservation of Antarctic Seals and any future commercial harvest would have to be regulated through these international agreements (Reijnders et al. 1993).

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