Seals as Prey for Orcas, Great Whites and Polar Bears | Sea Life, Islands and Oceania

SEALS AS PREY

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Great white shark
Seals are fed on by sharks and killer whales. Sometimes pups are taken by foxes on land. In Namibia seal pups are sometimes taken by lions and jackals Great White's sometimes even eat elephant seals. Once a large great white found off of California was dissected, revealing large chunks of elephant seal inside its stomach, including a completely severed head.

Seals and sea lions are particularly known for being hunted by great white sharks. Great whites like to stalk their prey from behind and below, and then attack, taking a massive bite and then waiting for their victim to bleed to death. They often sneak up on sea lions, seals and elephant seals from below and attack from behind. They usually take a powerful first bite underwater and the first indication on the surface is a large slick of blood. Minutes later, the victim appears on the surface with a large chunk missing. The shark thne appears and finishes it off.

Great whites have been observed shooting vertically upwards from a depth of 10 meters and knocking their prey right out of the water to stun it. Off South Africa great whites have been seen leaping five meters out of the water with a seal in their mouth. The impact stuns the prey and often leaves it with a chunk taken out it. The sharks then attack again or wait for their victims to bleed to death.

Websites and Resources: Animal Diversity Web (ADW) animaldiversity.org; National Oceanic and Atmospheric Administration (NOAA) noaa.gov; Fishbase fishbase.se; Encyclopedia of Life eol.org; Smithsonian Oceans Portal ocean.si.edu/ocean-life-ecosystems ; Monterey Bay Aquarium montereybayaquarium.org ; MarineBio marinebio.org/oceans/creatures

Seal-Eating Orcas

In the Antarctic two orca populations — not subspecies, but different groups that overlap at the margins — used very different hunting techniques, taught across generations. Some Antarctic orcas use the cunning tactic of hunting in packs and making waves to wash seals off floating ice.

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Killer whale attacking a seal
In Antarctica transient orcas skyhop to look for seals floating on ice floes. When seals are located various strategies are used to knock them off the floes and attack them in the water. Antarctic transients have been observed creating large waves that wash seals off of ice floes into the water, tilting the ice flows until the seals fall off, or ramming the ice floe hard enough so it breaks apart. In one instance a transient orca was observed leaping onto an ice flow to grab a seal. The whale was then pulled back into the water by two pod members who grabbed the whale by its fluke.

On the sharply sloping beaches of Patagonia in Argentina orcas sometimes ride waves right on to the beach and beach themselves to capture seal lion pups and even adult elephant seals. Orca mothers teach the technique to their offspring how to beach themselves so can catch seals sunning themselves.

Great White Sharks Attack of Seals

Peter Klimey of the University of California has videotaped more than 100 attacks by great white sharks of elephant seals, sea lions and harbor seals at the Farallon Island, a group of rock islets west of San Francisco. Recalling an attack of an 400 pound elephant seal, Klimley told Time magazine, "It was stunning. The shark ambushed the seal, then came back several times to take three or four bites out of it. I had never seen anything like it...The white shark is a skillful and stealthy predator that eats with both ritual and purpose." Klimley told Discover, "The sharks appear to attack from ambush. From a seal's perspective, the dark grey of the sharks' backs could blend almost perfectly with a rocky bottom, and heavy surf could further serve to obscure them. The area of the best attacks...is one that provides them with the best camouflage."

One of the best places to see great white sharks is offshore from Seal Island in False Bay, near Cape Town in South Africa. Large sharks are routinely seen here leaping from the water with seals in their mouths. The waters around Seal Island are a favorite feeding area for great white sharks. On the flat, rocky island, a third of a kilometer long, 60,000 Cape fur seals gather. The seals are often attacked in the morning as they leave the island for their feeding ground 60 kilometers out in the bay. The attacks generally occur in the hour after dawn, because, scientists think, after that time, the seals can see the sharks approaching them from underwater and can escape. In the morning the seals are often jittery. Shark expert Alison Kick told Smithsonian magazine, “They want to go to sea to feed but they’re afraid of the white sharks.”

Polar Bears and Seals

Polar bear hunt seals. They wait for coastal waters to freeze on then live a solitary life of seal hunting. The bears often ignore the meat and gorge themselves on the fat, which they need for energy.

Polar bears mainly hunt seals using two methods: by stalking seals from land or underneath ice after they have emerged at breathing holes; or by waiting patiently near the seal's breathing hole and biting its head as it surfaces.

Polar bears are so strong they can reach in hole of ice, kill the seal with a single, crushing bite and then pull it out of the water its strong neck and shoulder muscles.

A favorite polar bear prey is seal pups that are born in the spring in little caves hollowed out of snow rifts by their mothers above their breathing holes in the sea ice. The seals are well hidden but the bears can locate the pups with their amazing sense of smell. The polar bears kill the pups with a bite to the head. The 50 pound animals are almost half fat.

Cannibalism Among Seals and Sea Lions

Cannibalism has been observed among grey seals in Canada, elephant seals in Argentina and the New Zealand sea lion ( Phocarctos hookeri ). On the New Zealand sea lions, Adam Lusher wrote in the Electronic Telegraph, “Scientists who studied the population structure of a breeding colony at Dundas Island were amazed to see 47-stone males grabbing pups which weighed only about two stones, dragging them into the sea and devouring them. As the mothers called plaintively from the shore, the males bit off the pups' limbs and shook their bodies with such ferocity that the carcasses were hurled out of the water. [Source: Adam Lusher, Electronic Telegraph, October 2000]

Dr Ian Wilkinson, the biologist leading the study, said: "We were shocked. The male would come ashore, grab the pup, swim out 50 or 100 meters with it, shake it around, kill it, and then bite off chunks and limbs and eat them...When it was happening, we would see whole groups of seabirds gathering nearby. Then all of a sudden, you would see a pup come flying out of the water and watch the carcass splash down. It's never pleasant to see that sort of thing. I don't think anybody enjoys seeing animals kill other animals."

In 12 weeks, the scientists recorded 24 cases of cannibalism at Dundas Island, 200 miles south of New Zealand, where up to 300 pups are born every year. Eleven killings were witnessed during the first study period in early 1999 and a further 13 occurred in January and February of 2000. Dr Wilkinson, of the New Zealand Department of Conservation, said: "We saw the male grabbing the pups on two occasions. We saw them eating the pups in a further 22 cases. In one instance we saw the mother bite the male, who dropped the pup and bit her. He was twice or three times her weight. There was nothing she could do. When the male took the pup away, the mother called as she would when returning from a feeding trip. She sat on the rocks calling for about 25 minutes."

The New Zealand (or Hooker's) sea lion, is one of the rarest sea lion species in the world. Dr Wilkinson said the cannibal males could be killing about two per cent of a population of between 13,000 and 17,000. "It is not good for the species as a whole, but maybe it is a clever feeding strategy for the individual males involved. It is very difficult to speculate on why they do it. Maybe it's because the pups are an easy source of food. Normally they might have to swim out and dive to 300 or 400 meters to catch squid. But a single pup is enough to meet their daily needs for food, and they don't have to expend huge amounts of energy to get it."

Cannibalism is common in many other species, and has been recorded in at least 100 mammals, including man. Dr Wilkinson said: "There are several reasons for cannibalism. As well as killing for food, adults will kill unrelated young to increase their access to food or breeding sites for themselves and their offspring. A third reason is sexual selection, where males kill unrelated offspring. This is common in lions. When a male takes over a pride, he will often kill all the pups, because the females will then come into season and he can produce offspring of his own."

Image Sources: Wikimedia Commons, NOAA

Text Sources: Animal Diversity Web (ADW) animaldiversity.org; National Oceanic and Atmospheric Administration (NOAA) noaa.gov; Wikipedia, National Geographic, Live Science, BBC, Smithsonian, New York Times, Washington Post, Los Angeles Times, The New Yorker, Reuters, Associated Press, Lonely Planet Guides and various books and other publications.

Last Updated June 2023