With a long, protruding snout, pale, tan fur, and an affinity for ice floes, the crabeater seal (Lobodon carcinophagus) is one of Antarctica’s many interesting species of pinnipeds.
Where Do They Find Crabs in Antarctica?
There aren’t many species of crabs that live in Antarctica, and despite the obvious-sounding name, the crabeater seal does not actually eat any crabs. The name was a mistake made by early whalers and sealers who seemed to think they loved a good hard-shelled meal. Despite the obvious mistake, the name stuck, much to the dismay of current scientists and crabeater seals everywhere. Instead, their diet is comprised primarily of krill. Cephalopods and Antarctic fish also make up a smaller portion of their diet. Their highly specialized, lobed teeth allow them to swim through swarms of krill and filter out the tiny crustaceans from seawater like a sieve. With these specialized teeth, they can eat large quantities of krill every day without exerting much energy.
Whaling and Crabeater Seal Populations
Currently, scientists believe that there may be as little as seven million individuals, and as many as 75 million individual crabeater seals living in Antarctica, making them the most abundant seal in the world! Since their range is restricted to Antarctica, this interesting fact quite often goes unnoticed by the general public. How are there so many crabeater seals in Antarctica, though? During the 1800s and into the 20th century, large numbers of baleen whales, whose one and only food source is krill, were slaughtered throughout Antarctica. With little to no competition for food, crabeater seals and other Antarctic wildlife began seeing upward trends in their populations. It will be interesting for marine scientists to observe how crabeater seal and other marine populations that depend on krill begin to fluctuate now that whaling is strictly illegal in Antarctica.
Seal Pups on the Ice
The crabeater seal breeding season takes place primarily between September and November. Although scientists cannot be completely sure, it is suspected that both courtship and mating take place in the water. Occasionally, they may haul out on sea ice floes to find mates. While other species of seals will aggregate together to give birth to their pups, the crabeater seal takes a different approach. Pregnant females will haul out on ice floes by themselves and give birth to a single pup, which they will nurse for three weeks. Some time later, the male will haul out alongside the female and pup and fiercely defend his new family. The male that shows up may not be biologically related to the seal pup, and is more interested in mating with the female once she goes back into estrus. Pups are born weighing 44lbs. (20 kilograms), and by the end of their three-week nursing period, they can weigh up to 240lbs. (110 kilograms)! The mother seal’s milk is high in fat and protein, a perfect combination for surviving the upcoming winter.
What Eats a Crabeater Seal?
However plentiful the crabeater seal’s populations may be, they still frequently fall prey to two of Antarctica’s top predators. The leopard seal, one of Antarctica’s most voracious eaters, is responsible for 80% of all crabeater seal pup deaths. Like many other seal species, young crabeaters that have recently left their parents for open waters are seldom safe. Killer whales, or orcas, are also known to eat both pups and adults throughout their range. To deter predators, crabeater seals will aggregate on ice floes and in open water in groups of up to 1000 individuals. Surely, there’s safety in numbers!
Where Do the Crabeaters Go?
When winter begins to set in, the crabeater seal will begin to migrate into northern parts of Antarctica where the water usually is a bit warmer. Occasionally, however, their internal compass can sometimes not be trusted. There have been reports of crabeater seals that migrate a little too far north and end up in South America, New Zealand, or even South Africa. These occurrences are rare, and can be deadly for an animal that lives in freezing temperatures for most of its life.
Threats to Crabeater Seals
One of the major threats currently facing crabeater, and all Antarctic seals, is climate change. Declining in sea ice throughout Antarctica has led to an abundant decline in krill populations that depend on sea ice for breeding and feeding purposes. With declining krill populations, crabeater seals may see an overall decrease in their populations throughout time. There just simply won’t be enough krill to feed the millions of seals that currently inhabit the continent.
Seeing as the crabeater seal is the most specious seals in Antarctica, they’re definitely an easy spot on any Antarctic cruise expedition. Make sure to keep an eye out for ice floes- they’ll most likely be lounging on the ice, calmly watching you pass by!