Serge Ouachée / Wikimedia Commons Bird flu has devastated southern elephant seal populations in ArgentinaSerge Ouachée / Wikimedia Commons
A highly contagious strain of the H5N1 bird flu virus has devastated populations of southern elephant seals (Mirounga leonina) in Argentina. In October 2023, biologists from the Wildlife Conservation Society visiting the Valdes peninsula on the coast of central Argentina found a 13-kilometer beach strewn with elephant seal corpses: 70% of the 1,891 pups had died. In the same location, at the same time the previous year, the mortality rate was just 0.8% of 3,135 pups. Similar findings were made on other beaches. It is estimated that more than 17,400 pups—96% of the total—may have died from the virus, later identified by the Argentine government’s Animal Health Service. At one of the sites, where the biologists expected to find thousands of weaned pups, there were only 58. Almost an entire generation of elephant seals was lost in the region. As adults, males of the species are three to four times larger than females. The largest weigh up to 4 tons and measure more than 6 meters (m) long, although the average male weighs around 2 tons at 4 m long, while the average female is 500 kilograms at 2.7 m. Taking this event into account, the number of birds and mammal species known to be affected by avian flu increased to 345 (Marine Mammal Science, December 25, 2023; ScienceAlert, January 23).
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