Scientists have long wondered why whales travel up to 18,840 kilometers every year between their feeding grounds in polar waters and warmer, tropical seas. Previously, researchers thought that after feeding in the Arctic or Antarctic, whales traveled to the tropics to give birth far from their usual predators.
To find out the real reason for the migrations, researchers deployed 62 satellite tags on the four types of killer whales that inhabit Antarctic waters. After tracking the whales over eight southern summers, the scientists found that some journeyed as many as 9400 kilometers to the western South Atlantic Ocean, making the round trip in merely 42 days. But they didn’t do it to give birth.
The researchers already knew that whales, like humans, shed outer skin cells continuously. But in the cold Antarctic seas, the whales are apparently unable to shed its skin. Instead, they build up a thick, yellow film of microscopic diatoms on their skin. High concentrations of diatoms can accumulate potentially harmful bacteria, adversely affecting the whales.
To conserve body heat in cold Antarctic waters, whales divert blood flow away from their skin. This causes a slowdown in skin cell regeneration and ultimately drives the whales to warmer waters, where their metabolism ratchets up. This new research thus concludes that the whales migrate more than 5000km every year just to shed their skin and accumulate a healthy skin.