Rising seas. Increasing disease threats. Accumulated chemical pollutants in top predators.
All this spells trouble for marine mammals in Hawaiian waters, especially two of the most endangered species: monk seals and the insular population of false killer whales.
At recent meetings in Hawaiʻi and California, scientists studying these animals described the threats in detail. Three of the gravest threats are:
- Sea level rise. This has diminished the land available for monk seals to bear their pups. The three main pupping islands at French Frigate Shoals have disappeared and seals are crowding onto other islands.
- Avian influenza. A new variant H5N1 has shown up in marine mammals from Washington state to Antarctica. Experts fear seabirds could carry it to Hawaiʻi and transmit it to monk seals, dolphins, and other marine mammals.
- Toxoplasmosis. This parasite, spread by cats, is a leading cause of monk seal deaths in the Main Hawaiian Islands. It is also known to have led to the deaths of spinner dolphins in the islands.
Of these, maybe the most troubling is what is occurring globally with the spread of highly pathogenic avian influenza (HPAI H5N1). In Argentina, an outbreak of avian influenza killed 70 percent of the elephant seal pups born in the 2023 breeding season. Mortality rates were almost 100 percent by early November in the area of Penísula Valdés, where more than 17,000 pups died.In Peru, more than 5,000 sea lions died of the highly pathogenic avian flu, according to a report published by the Centers for Disease Control.
At a meeting of the Pacific Science Review Group, which advises the National Oceanic and Atmospheric Administration on compliance with the Marine Mammals Protection Act, scientists expressed alarm over the prospect of the highly pathogenic H5N1 arriving in Hawaiʻi, possibly carried here by seabirds. Elsewhere, in South America, the South Atlantic, and even Antarctica, thousands of birds have died after becoming infected with a highly contagious, highly deadly variety of avian influenza.
In January, the Wildlife Conservation Society issued an urgent warning that the virus threatens wildlife across the globe. “H5N1 now presents an existential threat to the world’s biodiversity,” said Chris Walzer, the group’s executive director of health, in a news release.
“It has infected over 150 wild and domestic avian species around the globe as well as dozens of mammalian species. The bird flu outbreak is the worst globally and also in U.S. history, with hundreds of millions of birds dead since it first turned up in domestic waterfowl in China in 1996.”
The Centers for Disease Control has said that the risk is low that this highly contagious, highly pathogenic avian influenza – (HPAI) – might spread to humans from mammals, even though “a small number of sporadic human cases … have been identified since 2022,” all associated with poultry exposures.
However, at least one person in Texas appears to have contracted avian flu from cattle. Herds of cattle in states ranging from Texas to Idaho to Michigan have now been infected with the highly pathogenic avian flu, according to the U.S. Department of Agriculture. The USDA has detected HPAI H5N1 in wild mammals in every state along the Pacific Coast.
The Wildlife Conservation Society’s Walzer noted that globally, the highly pathogenic virus “has now infected many mammals – including foxes, pumas, skunks, and both black and brown bears in North America. Some 700 endangered Caspian seals died from HPAI near Dagestan in 2023…. HPAI H5N1 has arrived in Latin America with devastating consequences.”
Should avian flu arrive in Hawaiʻi and infect monk seals, the result could be disastrous. The entire population of monk seals is estimated to be just around 1,600 animals, most of them found in the Northwestern Hawaiian Islands, with around 400 in the Main Hawaiian Islands.
The National Oceanic and Atmospheric Administration does have a disease outbreak plan for monk seals, as well as preparedness plans for other disasters, both natural and human-induced, according to Shanelle Naone, public information officer for NOAA in Honolulu. That plan, she said in an email, “is focused on morbillivirus,” but added, “we are working to adapt these preparedness efforts to HPAI H5N1.” Among other things, she said, NOAA is partnering with the University of California-Davis “to explore and test the utility of bench-top analyzers that are rugged and portable and have the potential to detect influenza in about an hour; these will be particularly useful for remote parts of the species’ range.”
And, since the presence of avian influenza in the islands would likely be seen first among birds, Naone said, “we are working with agency partners who study and surveille avian wildlife. … We also have arrangements to submit monk seal samples to one of the primary diagnostic laboratories that is being used to analyze other pinnipeds in the United States.”
“Our current focus, also in collaboration with other agencies, is on remote areas of the Papahānaumokuākea Marine National Monument, as we are preparing for the upcoming field season. We want to equip field researchers with all the information they need to look for indications of influenza in wildlife and report back.”
The vulnerability of marine mammals that do not rest on land is difficult to assess. But in 2022, a stranded porpoise in Sweden and a bottlenose dolphin were found to have died as a result of H5N1 infection, as well as two dolphins and a harbor porpoise in England in 2023.
A report in The New York Times on the 2022 strandings quoted Richard Webby, a virologist at St. Jude Children’s Research Hospital. “Our surveillance activities on a global scale are never sensitive enough to pick up the only two events of this kind,” Webby told the paper. The discovery of avian flu in two different species on two different continents suggests there have “almost certainly” been other cases, Webby was quoted as saying.
Recently, reports have proliferated of stranded whales and dolphins suspected of having been infected with avian flu. In February, an outbreak of H5N1 was detected in the population of wandering albatross on the South Georgia islands, having earlier been detected among brown skua and kelp gulls.
Should the virus arrive in Hawaiʻi, it could pose a serious threat to the survival of not only monk seals, but also the endangered insular false killer whale population (numbering fewer than 170 individuals) as well as albatross, other seabirds, and even endangered native forest bird populations.
— Patricia Tummons
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