It may be one of the strangest things you’ve ever seen: a dolphin swimming through the waters of the ocean with a sponge fitted over its beak. What in the world? The intelligent marine dwellers have found a way to protect their faces as they scour the rocks and broken coral for food stuffs. Rather than tearing the skin on the beaks and faces, they have devised this ingenious tool to be able to safely forage.
Researchers had thought, at first, that it would simply make more sense for the dolphins to feed from the mid-waters rather than along the bottom of the sea. In fact, the fish and crustaceans that inhabit the bottom of the ocean are more nutritious for the Shark Bay dolphins. The dolphins must have known this all along; developing a method of hunting safely instead of turning to other food sources that provide a less sound diet.
After studying the behavior of these dolphins, researchers found that hunting with sponges is an activity primarily carried out by the female of the species. It is thought that this is because of the pressures faced by a mother who has to rear her young for almost 5 years at a time. As the young swim and forage with their mother, they learn the interesting sponging technique which they, then, pass onto their young.
Sponge fishing works as such: a Shark Bay dolphin will fit a sponge onto its beak and scrape it along the bottom of the ocean. A fish will scare up from the bottom, the dolphin drops its sponge, heads to the surface for a breath of air and then dives down for its meal. The emerging fish will swim for several meters before it attempts to rebury itself, giving the dolphin the time it needs to drop, breathe and dive. A study conducted by Eric Patterson, a graduate student at Georgetown University, showed that by sponging, a dolphin can scare up a prey fish about every 9 minutes, making hunting in this manner extremely rewarding.