Everyone knows what a dolphin is. They are easily recognizable small-toothed cetaceans with a curved mouth, giving them a permanent “smile.” Everybody loves dolphins, as they are celebrated for protecting shipwrecked sailors and spending their days frolicking happily in the waves. However, a dark truth lies behind their fake smile. Growing evidence shows that the big animals are killing fellow mammals in droves. Dolphins have been found to bludgeon porpoises to death by the hundreds. Unlike most animal killers, which eat their prey, dolphins seem to have murderous urges unrelated to the need for food.
Most dolphins are marine and live in the ocean or brackish waters along coastlines. The largest dolphin, the orca, can grow to be over 30 feet long. The smallest, the Maui dolphin, is just five feet long. Dolphins feed chiefly on fish and squid, which they track using echolocation, a built-in sonar that bounces sound waves off prey and reveals information like its location, size, and shape.
Behavior and Reproduction
Dolphins are intensely social mammals that communicate with squeaks, whistles, and clicks. Whether dolphins have language, as humans do, is a topic that scientists have debated for decades.
As mammals, they have warm blood and nurse their young. Dolphins have more than one mate, and generally produce a single offspring that will stay with the mother for up to six years, depending on the species. Dolphins are graceful, sleek swimmers that can reach speeds of more than 18 miles an hour. They are also playful and often frolic in a boat’s wake, leaping out of the water.
For centuries, people have hunted dolphins for their meat and blubber. Today, their main threat comes from being caught accidentally in commercial fishing nets. For marine dolphins, warming ocean temperatures because of climate change have caused some of their primary food sources to move into deeper, cooler water. Furthermore, marine heatwaves, also caused by climate change, appear to have a negative effect on dolphins' reproductive rates and ability to survive.
Dolphins have even been observed in recurring acts of infanticide. Off Scotland, a scientist watched in shock for nearly an hour as an adult dolphin repeatedly picked up a baby in its mouth and smacked it against the water, over and over, until it sank from view.Off Virginia, researchers found at least nine baby dolphins killed, their ribs broken, their skulls and vertebrae smashed. One small body bore puncture marks matching the pattern of adult dolphin teeth. Dolphins also have been observed to murder porpoises and other mammals for fun. These murderous urges could soon affect beachgoers, forcing them to stay out of the water.
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