Australian fur seals are shedding: there seems to be an association with pollution

TO Deen Maar a small island off the coast of South Australia something unusual is happening: some Australian fur seals (Arctocephalus pusillus doriferus) they are losing large portions of their fur. Sea lions, not to be confused with seals, are a family of marine mammals belonging to the Pinnipeds and are also distinguished from seals by the presence of small external auricles.

And what might seem like simple hair loss is not a cosmetic problem at all. For these animals fur is essential to limit heat dispersion and losing it increases the costs of thermoregulation. The specimens affected by alopecia have in fact resulted in worse body conditions compared to healthy animals and the greater energy demand to maintain body temperature could increase the risk of mortality. Studies have also hypothesized that this increased mortality, especially among young females, may have contributed to the decline in pup production observed in the colony.

For years, scientists have been trying to understand what causes this mysterious alopecia. Viruses, bacteria and parasites seem not to be the explanation, while several studies have found it in affected animals differences in fur composition and higher concentrations of some metals and persistent organic contaminants. This does not mean that it has already been proven that pollution directly causes hair loss, but it suggests an important lead: to understand what is happening to the seals we must perhaps look much further than the island on which they live.

When losing hair is a problem for survival

Fur seals do not simply make them “hairy.” It’s a real one barrier against the cold. In fact, fur seals have a thick undercoat, made up of very thin hairs, protected by longer and more resistant hairs. This structure helps limit heat loss when animals spend long periods in cold waters.

Losing hair, therefore, can have much more serious consequences than we imagine. A study published in Journal of Mammalogy analyzed the mysterious alopecia present in the colony of Lady Julia Percy Island, now also known as Deen Maarobserving that the hair loss was mainly due to breakage of the hair shaft above the skin. The researchers found no evidence of viral, bacterial, fungal or parasitic infections to explain the phenomenon.

However, the analyzes identified other differences between healthy and affected animals. Sea lions with alopecia had, for example, lower concentrations of zinc and tyrosine in hairtwo elements that could contribute to the resistance of the hair structure. At the same time, they also showed higher levels than some heavy metals and persistent organic contaminants. Hence one of the most interesting hypotheses arises: fur loss may not depend on a single pathogen, but on a combination of nutritional and environmental factors.

And for a fur seal this can become a real problem. If the fur loses its insulating capacity, the animal may lose more heat in the water and have to expend more energy to keep its body temperature stable. In the young individualswho still have to grow up and face the difficulties of life at sea, a problem of this type could therefore represent a further risk factor. According to data provided by Dave Williams of the Eastern Maar Aboriginal Corporation (the association that deals with the protection of Australian fur seals) in an interview with ABC News, the pups have gone from 2,000 to 700 in just twenty years in the last census in February 2026.

What does pollution have to do with alopecia in seals in Australia

Here the story becomes even more interesting. Sea lions are predators that occupy high levels of the marine food web: they feed on fish, cephalopods and other organisms which may, in turn, have come into contact with substances present in the environment.

Some contaminants have a particularly problematic characteristic: they don’t disappear easily. So-called persistent organic contaminants, or POPs (Persistent Organic Pollutants), they can remain in the environment for a long time and accumulate in organisms. When an animal eats another contaminated organism, it can take in those substances itself. Moving up the food chain, some contaminants can then reach high concentrations in large predators: a phenomenon known as biomagnification.

A 2018 study compared the fur of seals with alopecia to that of unaffected animals. The researchers found significantly higher concentrations of some dioxin-like polychlorophobiphenyls (PCBs) in individuals with the syndrome and they also identified other contaminants, including dioxins, furans and brominated flame retardants. However, the result does not prove that these substances are the cause of alopecia: it shows that it exists an association which deserves further investigation.

And it is precisely here that we must avoid an overly simple conclusion. We cannot yet say: “pollution is causing fur seals to shed”. The relationship between contaminants, nutrition, environmental conditions and animal health is much more complex. The same studies underline that several factors could be involved at the same time.

But seals could still tell us something important about the environment in which they live. As predators placed high in the food web, they can function as real sentinels of the ecosystem: Analyzing the substances present in their tissues can help scientists understand which contaminants are circulating in the sea.

This is why today researchers are trying to follow the movements of animals and understand where they find food and where they could come into greater contact with pollutants. The goal is not only to find out why some seals are losing their fur, but to reconstruct a problem that could start far away from that small Australian island.