Tiger sharks are among the fiercest hunters in the world. However, a study published in Springer’s journal Behavioral Ecology and Sociobiology shows that these sharks are not above turning into scavengers.
A team of researchers from Australia, the US and the UK tagged and studied tiger sharks and green turtles around Raine Island off the northern coast of the Great Barrier Reef for five years. They found that thousands of female green turtles die during the nesting season due to exhaustion, and the sharks take this opportunity and feed off the carcasses washed into the sea, a behavior that allows them to save energy that they would otherwise spend actively hunting.
The tiger sharks swim near the shore where the turtles reside instead of swimming in deep water, which they normally do when hunting. Despite the presence of the sharks, the turtles did not manifest any behavior that is associated with avoiding predators. The research team concluded that the behaviors of these animals prove that the sharks were not hunting the turtles and were simply waiting for some to die.
“For any predator, hunting and capturing prey is energetically demanding and inherently dangerous,” says lead researcher Neil Hammerschlag of the University of Miami Rosenstiel School of Marine and Atmospheric Science in the US. “At Raine Island, although sharks can encounter and hunt thousands of healthy green turtles, the large numbers of dead and dying animals that get washed into the water during the nesting season makes it far more profitable for the sharks to scavenge on these carcasses rather than to chase live turtles, given the possibility of wasted time and energy when predation attempts are unsuccessful.”
This behavior is not unique to the sharks, according to the researchers. Apparently, in spite of the abundance of food, predators like hyenas and lions also turn into scavengers.