Quirks & Quarks

Whales may migrate to warm water for a full body exfoliation

The mystery of why whales undertake long and arduous migration may come down to skin care

The mystery of why whales undertake long and arduous migration may come down to skin care

Female killer whale and newborn calf in Wilhelmina Bay, Western Antarctic Peninsula. A heavy yellow coat of diatoms covers the female (A. Schulman-Janiger)

Originally published on February 29, 2020.

Whales are known to embark on some of the longest migrations on Earth, from freezing polar regions to warm tropical waters. The reason why they travel so has never been entirely clear to scientists, but according to new research, it may simply be to improve their skin.

Researchers had hypothesized that they might be seeking better food resources, or to find clement conditions in which to bear their young. However these explanations have been unsatisfying as there are actually reduced feeding opportunities in warmer waters, and some whales calve in cold water. 

Now new research suggests a primary reason for migration might be to rejuvenate their skin.

Antarctic killer whales migrate to warm water to shed the yellow coating of diatoms (SR3/NOAA Fisheries)

Whales have a lot of skin in the migration game

According to a new study by Robert Pitman, a marine ecologist in the Marine Mammal Institute at Oregon State University and his colleagues, the shedding of skin is an important physiological need for whales that could be met by migrating to warmer waters.

Pitman hypothesizes that in cold water, whales conserve body heat by diverting blood away from their skin. This reduces the regeneration of new skin cells. In warm water however, whales don't need to worry about heat loss. So they increase circulation of blood to the skin, which revives their skin metabolism so they can generate new skin cells, and shed old cells.

Minke whale in the Gerlache Strait, Western Antarctic Peninsula. The snowy white ventral surface indicates a recent trip to a tropical spa (S. Hansen)

A long way to go for skin care

Pitman's evidence for his case is that whales in frigid waters are often discoloured by a thick yellow coating of microscopic diatoms, a group of ocean-dwelling single-celled algae. Previous studies have shown that high concentrations of diatoms on the skin of Antarctic killer whales may accumulate bacteria that is harmful to the skin. Shedding skin also sheds this this harmful coating.

The yellow-tint of this Minke whale in the Antarctic's Drake Passage indicates that it is covered in diatoms (J. Durban)

Pitman and his team satellite 62 Antarctic killer whales to track their migration — as far as 11,000 kilometres — to tropical waters and back. Most of those migrations were very fast, non-stop and largely straight north then back. Such a migration would be too fast for calves to keep up, so the only explanation for this migration according to Pitman is the maintenance of healthy skin by moulting. The whales returned to the Antarctic free of their yellow diatom layer.

Written and produced by Mark Crawley


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