Seals in Mexico are losing fur and climate change may be to blame

Alopecia makes it harder for fur seals to keep warm, and the condition may be the result of hotter temperatures making it tough to find their preferred prey.

Some fur seals in the Pacific Ocean are losing their fur, and dietary changes brought on by climate change may be responsible.

A fur seal with patches of hair loss in the San Benito archipelago, Mexico
Dr. Fernando Elorriaga-Verplancken

Alopecia, a condition that involves the loss of hair, can massively affect the ability of these animals to keep warm, says Karina Acevedo-Whitehouse at the University of Queretaro in Mexico. “Fur seals rely heavily on their double layer of fur in order to achieve adequate thermal insulation,” she says.

She and her colleagues collected fur samples from 13 Guadalupe fur seals (Arctocephalus townsendi) in the San Benito archipelago off the west coast of Mexico between 2017 and 2018.

The team analysed these using scanning electron microscopy and X-ray spectroscopy to determine how healthy the hair follicles were.

Nine of the seals showed visible signs of alopecia, but all of them appeared to have unusually brittle hair.

“Structural changes, although less severe, were detected even in samples collected from fur seals that appeared to have normal fur,” says Acevedo-Whitehouse. “This suggests that the changes are gradual and this alopecia only appears after the fur has undergone extensive structural damage.”

Microscopic analysis of the hairs ruled out the presence of bacteria, fungi, mites or lice, which are all possible causes of alopecia. The team didn’t test for viral causes of alopecia, but analysis of the underlying skin suggests that it was healthy and there were no signs of inflammation or lesions that are commonly found in animals infected with viruses.

The gradual change in the structure of the hairs suggests that nutritional deficiencies are probably the reason for the hair loss, says Acevedo-Whitehouse.

Sea surface temperatures in the area have risen consistently in the past few years. Fur seals typically live on a diet of fish and squid, but previous studies have found that in hotter conditions, they feed more on a different species of squid that appears to be less nutritious.

This is probably because hotter temperatures lead to the preferred prey being less available to the seals, so they have to turn to other food, says Acevedo-Whitehouse.

These nutritional changes could have an impact on the proteins required to maintain strong hair follicles, she says.

Rachael Gray at the University of Sydney, Australia, says she is sure we will see more impacts of climate change on marine mammals. “This could be due to the impact of changing prey or habitat availability occasioned by increasing sea temperatures,” she says.

Journal reference:

bioRxivDOI: 10.1101/2023.04.02.535308

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