It's always been kind of a mystery. Why do Antarctic Killer Whales migrate to tropical waters every year? They don't seem to follow a certain feeding route. The migration to tropical waters has nothing to do with breeding or giving birth. So why do they do it?
Well, it turns out they migrate to tropical waters so they can shed the upper layer of skin, the upper epidermis, without losing so much heat. It would be impossible for these whales to shed their outer skin in the frigid waters (the temperature is lower than freezing) of the Antarctic Ocean because they'd lose so much heat they might die. So, the take a quick trip to the tropics, shed their skin there, and the quickly return.
You can think of as an exfoliating treatment at the spa! The Killer Whales migrate more than 5000 miles to do this and they only stay about 45 days before returning home. These migrations take place between February and April.
Shedding the outer layer of skin is a way of cleaning the body of all the algae and invertebrates that have taken up residence there. This also repairs the skin. Scientists figured this out by fitting 12 killer whales with satellite transmitters. 6 of the transmitters got lost but the other 6 remained attached and they were able to follow them closely and take videography. The scientists could clearly see that their skin was encrusted when they started out and clean as a whistle when they returned.