A lone fur seal upended the conventional wisdom seals are cute and cuddly creatures by singlehandedly attacking a gam or school of 10 blue sharks in the waters off South Africa.
A video taken by a professional diver showed this lone African fur seal eat five of the sharks without itself being attacked. Seal attacks on predators such as sharks are extremely rare and might illustrate some unknown behavior in these seals.
This very uncharacteristic behavior has left scientists puzzled and led to a study that tried to explain the reason for this extraordinary event.
A recent study published in the African Journal of Marine Sciences said this predatory behavior by the seal could also have important implications for our understanding of the food chain in the open ocean, meaning species thought to serve as prey might also become predators given certain conditions.
The video was taken in 2012 by Chris Fallows, who operates a company in South Africa that takes tourists on dives to see sharks first hand.
In December 2012, he was leading a dive group in the waters off Cape Point, a peninsula near Cape Town, when he noticed a gam of 10 blue sharks. These sharks normally measure some four to five feet in length or about the same length as a fur seal.
He was taken aback when a single young, male Cape fur seal swam into the gam and started attacking the sharks one by one. Fallows reported that in each of the five attacks on these sharks, the seal ripped oven the shark's stomach and fed only on the shark's viscera (stomach, liver and intestines).
After gutting a shark's insides, the seal discarded the dead shark and did the same to the remaining four victims. Fallows said he was "impressed at the ease with which this seal was able to take these sharks," said the Smithsonian.
Fallows said he first saw a seal eat a shark in 2004, also in the same area.
In the new study, researchers from the University of Miami noted seals have been seen before occasionally attacking baby sharks or nibbling at dead sharks. They said Cape fur seals and blue sharks aren't known as predatory rivals.
But what intrigued the scientists was the seal's choosing to eat only the viscera while discarding the rest of the shark. Scientists reported this might be because the viscera contain the organs that are the richest in energy such as the liver and intestines.
Scientists don't know how often seals attack sharks but this episode has upended the conventional wisdom seals are only prey for sharks. Ecologists have long assumed seals eat mainly small fish not exceeding about a foot long.
Researchers now suspect shark-eating is a natural behavior for seals.