An epidemic of avian flu in Patagonia seems to be on the decline after decimating southern elephant seal populations for the final yr and half, with researchers discovering no new circumstances in latest surveys of the coast. However the restoration course of for a lot of colonies, which have been almost worn out in some areas, may very well be simply starting.

The H5N1 influenza hit populations of southern elephant seals (Mirounga leonina) and different marine mammals and birds in August 2023, spreading throughout a number of provinces of Argentinian Patagonia and sending researchers scrambling to check the outbreak. With circumstances now on the decline, researchers are turning their consideration to finding out the worst-hit colonies as they recuperate their earlier inhabitants numbers, a course of that might take a long time.

“There have been no mortality occasions from avian flu” noticed in the course of the latest surveys within the province of Chubut, mentioned Valeria Falabella, the director of coastal-marine conservation on the NGO Wildlife Conservation Society (WCS) Argentina. “The not-so-good information is that the variety of people, most notably reproductive females, was method beneath what was anticipated.”

The 300-kilometer (186-mile) shoreline of the Valdés Peninsula, a preferred breeding space for southern elephant seals, noticed 17,400 of the 18,000 pups die on the finish of final yr, in keeping with a December 2023 research in Marine Mammal Science. Normally solely roughly 180 die. The research described the spiking mortality price as “catastrophic.”

The flu possible jumped to marine mammals within the space from South American terns (Sterna hirundinacea), principally affecting elephant seals but additionally spreading to sea lions (Otaria flavescens) and fur seals (Arctocephalus australis), researchers mentioned. They anxious the flu would soar to different species, equivalent to orcas (Orcinus orca), which feed on seals, however that risk by no means appeared to materialize.

H5N1 influenza is current in chicken species throughout the globe and has precipitated outbreaks in poultry and dairy cows within the U.S., whereas additionally spreading to different marine mammal species in South America. In remoted circumstances, it has additionally unfold to people, actually because they’ve common contact with contaminated animals.

The speedy elephant seal die-off altered social buildings in lots of colonies, in keeping with a research in Nature Communications, with less-dominant grownup males changing lifeless alpha males. There was additionally a “patchy distribution” of females with pups, that are often extra densely packed collectively, in addition to deserted sick pups, the research mentioned.

Researchers from varied NGOs, universities and authorities companies have been monitoring elephant seal populations on the Valdés Peninsula for the reason that Nineteen Eighties. This most frequently takes the type of a land survey that includes strolling the seashores and manually counting the animals. When circumstances enable, in addition they conduct aerial surveys.

This yr, they didn’t determine any animals, alive or lifeless, with avian flu signs.

“We have been ready for a brand new outbreak,” Falabella mentioned. “It was one thing we anticipated and that was very doable. It was so fortunate that it didn’t occur as a result of one other blow like final yr — I don’t know what would have occurred to this inhabitants.”

Whereas the absence of flu circumstances is promising, Falabella mentioned the outbreak will pose long-term challenges. This season, WCS researchers discovered the full variety of elephant seals had decreased by as a lot as 66% in some areas in comparison with the earlier yr, whereas the variety of grownup females had decreased by between 30% and virtually 70%.

Male elephant seals can mate with a number of females, so extra females means extra alternative to breed.

The variety of weaned calves additionally dropped by 82%, they discovered. The diminished numbers have been a direct results of the excessive mortality charges throughout final yr’s outbreak.

Beforehand, researchers weren’t certain in regards to the mortality price in adults as a result of, in contrast to pups, many sick people have been in a position to swim out within the ocean to feed after which died out of sight. This yr’s preliminary findings counsel that extra adults died than researchers first thought.

For some populations, restoration might take years, Falabella mentioned.

Within the meantime, there isn’t a lot WCS and others can do to assist the colonies, besides proceed monitoring for potential outbreaks, as different strains of avian flu are circulating all through South America. In Chile, a pressure of the flu has hit varied marine mammal species within the very north of the nation right down to Patagonia.

Colonies will solely recuperate with a number of undisturbed seasons of breeding and molting (during which seals shed and substitute their fur and pores and skin), in addition to entry to ample meals, Falabella mentioned.

“This yr, we’re crossing our fingers. Hopefully, it can proceed like this,” she mentioned, noting that the seals are already on the finish of the reproductive season, which lasts from August to November.

Banner picture: Elephant seals on the Valdés Peninsula Photograph by Adriana Sanz/WCS. 

Citations:

Campagna, C., Uhart, M., Falabella, V., Campagna, J., Zavattieri, V., Vanstreels, R. E., & Lewis, M. N. (2023). Catastrophic mortality of southern elephant seals attributable to H5N1 avian influenza. Marine Mammal Science, 40(1), 322-325. doi:10.1111/mms.13101

Uhart, M. M., Vanstreels, R. E., Nelson, M. I., Olivera, V., Campagna, J., Zavattieri, V., … Rimondi, A. (2024). Epidemiological information of an influenza A/H5N1 outbreak in elephant seals in Argentina signifies mammal-to-mammal transmission. Nature Communications, 15(1). doi:10.1038/s41467-024-53766-5

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