New data reveals that moulting is one of the main reasons whales migrate to warmer waters. Sounds like they’ve cracked the code for the ultimate ocean skin care routine.
Whales can be split into two main categories: toothed and baleen. Toothed whales include sperm and killer whales while baleen whales (which have plates of keratin based whalebone in their mouths required for feeding) include blue and humpback whales. Both types venture on the longest-known migrations every year of any mammal, travelling between 15,000 and 25,000 kilometers each; that’s almost twenty times the length of Russia and back again.
Whales can be found in all the world’s oceans, but their prodigious journey often first begins in high latitude feeding grounds. This could be in Antarctica in the southern hemisphere during the warmer summer months, or in the Pacific near northern Japan or California during the summer, on the opposite side of the year in temperate-cold waters. As temperatures drop, the time approaches for the whales to voyage to warmer waters and lower latitudes. The whales will often travel to areas near Central America, like Hawaii, Costa Rica, as well as Taiwan and the Philippines. Whales in the southern hemisphere travel northwards towards these areas and northern hemisphere whales will travel southwards at different times due to reversal seasons in the hemispheres.
For over a century it has been a worldly notion that the purpose of such mileage to reach lower latitudes during the winter months has been for breeding and calving far away from usual predators in warmer seas; certainly not for food, as feeding possibilities are sparse in these areas during the winter months. However, the feeding/breeding paradigm has been argued with evidence of bowhead whales migration, or lack thereof, in the Arctic. These whales along with many other much smaller species and odontocetes live year round in the Arctic and sub-Arctic, calving and raising their young here. This demonstrated that there is no such impediment by polar latitudes on thermoregulatory systems in whales, restricting growth and development of newborn calves.
This has led to the research of scientists from Oregon State University, investigating the real reason behind these migration patterns. Following 62 satellite tagged Antarctic killer whales across their migration courses they found that the whales could conserve their body heat to -1.9℃ in subfreezing waters. This is achieved by decreasing blood flow to their skin, thereby reducing normal and continuous epidermal molting. Molting among cetaceans is both continuous and periodic, a much more respected physiological process than when you or I remember to exfoliate now and again. Shedding, repair and renewal of the whales’ hard integument takes place to remove dead skin and a thick yellow film that often builds-up on the whales’ skin made of microscopic diatoms which can harbour harmful bacteria. Research found that the travel to warmer temperatures allowed for the heat loss which is required for the whales to molt. The feeding/molting hypothesis was then proposed.
As researchers quoted an expert Inuit hunter who said, “Belugas go to the rivers for warmth. And like seals they moult their skins. They moult in the warm water,” it was originally thought that beluga whales may be the only species of whale to migrate for self-cleaning purposes, based on evidence of their migration to river estuaries in Alaska and Canada. However, this new evidence implies that killer whales and potentially more species of whale migrate for the same reasons. This suggests migration is an act of ancestral habit for quite possibly the longest skin care routine ever, meaning that our notion of whales as polar species who venture to the tropics for molting and breeding should actually be reversed to creatures of warm-water who migrate northward toward the poles for feeding.
image source: Tony Wu/naturepl.com