Great White Shark Attacks On Sea Otters Surge In Pacific

A strange pattern has emerged along the shores of the Pacific Ocean, as a staggering number of sea otters are falling prey to great white sharks, leaving scientists at a loss regarding the mysterious string of attacks.

So many of the marine mammals are being bitten by white sharks that researchers now note the phenomenon could hinder the species’ recovery, as National Geographic recently pointed out. In the first 13 years of this century, over 750 shark-bitten otters were discovered, and in the ensuing two years, another 270 were added to that count. As the population of otters along the California coast stands at just 3,000 individuals, the white shark attacks are a significant mortality factor, far outstripping all other causes combined, as Newsweek notes.

Although sea otters have fallen victim to white sharks for generations, scientists have been stymied by the recent attacks, as the sharks don’t actually prey on otters. Instead, the mammals are simply being bitten and then released, likely as a result of the fact that they don’t contain the proper nutrients sharks need for survival. Great white sharks most often prey on seals and sea lions, which possess a thick layer of calorie-dense blubber that is critical for the sharks’ survival. Sea otters, by contrast, insulate themselves by trapping air near their bodies, leaving them little more than balls of fur, bone, and muscle.

Therein lies the puzzle behind the attacks: For a white shark, sea otters aren’t an appetizing meal, yet the sharks are clearly the culprits. The bite patterns found on dead otters match great white shark jaws, and teeth from the species have even been discovered in some of the carcasses.

Researchers have posited several possible scenarios to explain exactly why the white sharks could be targeting sea otters. For one, the smaller animals present a silhouette in the water that can at times be remarkably similar to that of the white sharks’ primary prey. It has been theorized that much the same process is at work when surfers find themselves attacked by white sharks. In both instances, the sharks typically move on after the first “exploratory” bite.

It has also been suggested that it isn’t adult great white sharks, which spend most of their time far offshore, that are responsible for the attacks. Instead, researchers believe that a younger demographic of shark is to blame for the upswing in bites, as Chris Lowe of California State University’s Shark lab points out.

“It’s possible that so many otters make it back to the beach mortally wounded because they’re being attacked by very young sharks who aren’t very good at it.”

Scientists are also at a loss to explain why the rate of attacks has increased so dramatically since 2003. While the risk of a shark attack for humans has dropped dramatically in the last half century, there is evidence that the number of great white sharks off California has surged since the early 2000s. No one is entirely sure exactly how many of the predators inhabit the region, however, and the lowered number of attacks on humans seems to suggest that bite rates are not simply a function of a higher population.

A number of other factors could be at work behind the attacks, but the data is unclear at this point. Warming oceans have prompted juvenile white sharks to move closer to shore, where they are far more likely to encounter sea otters. Booming populations of sea lions and elephant seals may also be attracting white sharks to the same areas that sea otters inhabit, indirectly prompting the two species into contact.

Whatever the reason behind the upswing in attacks, scientists point to a crucial need for understanding the pattern, not only for the benefit of sea otters and great white sharks but so that researchers might also better comprehend the threats facing both species.

[Image via Terry Goss – Own Work | Wikimedia Commons | Cropped and Resized | CC BY-SA 3.0]