Slow-moving sharks are preparing to strike, just like in the movies
A new study from the National Institute of Polar Research in Japan has found that sharks slow down dramatically when they are hungry and ready to pounce on their prey. The research, which monitored sharks for up to 37 hours at a time, suggests that the slow, charging pace of the shark in the film Jaws is actually quite realistic.
After tagging eight great white sharks, the researchers discovered that the fish traveled at exceptionally fast speeds. When the sharks were ready for feeding, however, they were observed moving sluggishly.
For example, as the sharks approached a seal colony, they were recorded moving more slowly than what would be energy efficient for them. This behavior suggests that the sharks were stalling while they selected the best seal to attack.
“This strategy is as close to a ‘sit-and-wait’ strategy as is possible for perpetual swimmers, such as white sharks,” said Professor Yuuki Watanabe.
Sharks are unable to pump water through their gills, so they have to keep swimming to stay alive. In order to obtain the oxygen they need, they swim through the ocean with enough energy to force the water through their gills.
The experts tagged sharks off the coast of the Neptune Islands in Australia to examine how fast they usually travel. They witnessed the sharks slowing down to a speed that was completely unexpected because it would be so costly in terms of energy. The findings suggest that catching a nutrient-rich seal is worth the energy that is spent.
“Overall, our results support our hypothesis that white sharks aggregating near seal colonies adopt slow speeds that may be optimized to increase encounter rates with fast-swimming seals while reducing swimming costs,” wrote the study authors.
The research is published in the Journal of Experimental Biology.