Every day, thousands of migratory seabirds soar along Australia’s coastline. They travel vast distances, connect continents, and play an essential role in some of the world’s most remarkable ecosystems. Along with these extraordinary journeys, however, they can also carry diseases capable of travelling across international borders. For a continent with so many globally significant bird movements, that connection between migration, disease and wildlife conservation matters.
Highly pathogenic avian influenza (HPAI), commonly known as bird flu, includes a number of different virus strains. Among them, H5N1 has attracted global attention because of its rapid spread through wild birds and its growing ability to infect a wide range of mammal species. Around the world, H5N1 has affected animals that scavenge infected carcasses, prey on sick birds, or live in close proximity to large seabird colonies. As the virus continues to spread, scientists are paying close attention to what this could mean for Australian mammals.
Australia has now confirmed H5N1 in wild birds across multiple states, with evidence of local transmission in some wild bird populations. While no infections have been confirmed in Australian native mammals, the virus’s continued spread has intensified questions about which species may be most vulnerable if exposure occurs. This is not about predicting catastrophe. It is about understanding where risk may exist, why particular species may be vulnerable, and how preparation can help protect wildlife.
For an overview of H5N1 in Australia, including how the virus spreads and why it matters for wildlife, read our H5N1 Bird Flu in Australia article. For a chronological record of Australia’s outbreak, see our H5N1 Bird Flu Australia Timeline.
How Does Bird Flu Infect Mammals?
Although H5N1 is primarily a virus of wild birds, it is not limited to them. Over recent years, scientists have documented infections in dozens of mammal species across Europe, North America, South America and Antarctica. Most of these cases are believed to have resulted from direct contact with infected birds or contaminated environments rather than sustained transmission between mammals.
For many wild mammals, the greatest risk comes from the way they naturally feed. Scavengers may consume the carcasses of infected birds, while predators can become exposed by catching sick or weakened prey. Marine mammals may also encounter the virus through close contact with infected seabirds or contaminated coastal environments, particularly where large breeding colonies overlap.
In a small number of overseas outbreaks, researchers have also found evidence that H5N1 can spread from one mammal to another. This has been documented most clearly in farmed mink, where crowded conditions likely helped the virus pass between animals, and has also been suspected during outbreaks involving seals and sea lions. While these events remain relatively uncommon, they demonstrate that under certain conditions the virus can adapt to transmission within mammal populations.
The growing number of mammal infections has reshaped how scientists view H5N1. Although widespread outbreaks among mammals remain uncommon, the virus is now recognised as a significant wildlife disease capable of affecting far more than birds. This explains why scientists are paying increasingly close attention to species that scavenge, hunt or live alongside large numbers of wild birds.
H5N1 is just one of several diseases capable of affecting Australian wildlife, highlighting why disease monitoring has become an increasingly important part of conservation. To learn more about other diseases affecting Australia’s wildlife, explore our guide to Disease & Biosecurity.
What Has Happened Around the World?
The growing concern about H5N1 and mammals is not based on isolated reports. In their 2024 review, Recent Changes in Patterns of Mammal Infection with Highly Pathogenic Avian Influenza A(H5N1) Virus Worldwide, Pablo Plaza and colleagues documented an unprecedented expansion in both the diversity of mammal species affected and the geographic distribution of infections during the current H5N1 panzootic. Rather than being largely confined to birds, H5N1 has now been confirmed in dozens of wild and captive mammal species, prompting scientists to reassess the conservation risks posed by the virus.
Many of the earliest cases involved terrestrial carnivores and scavengers. Red foxes, bears, wild cats, otters and even polar bears have all tested positive for H5N1 after feeding on infected birds or carcasses. Although these animals are not natural hosts of the virus, their feeding behaviour brings them into close contact with infected wildlife, demonstrating how readily the virus can cross species boundaries under the right circumstances.
One of the most significant developments occurred in Spain during 2022, when an outbreak on a mink farm provided some of the strongest evidence that H5N1 could spread from one mammal to another under certain conditions. Researchers concluded that, after the virus was likely introduced by wild birds, it subsequently spread between mink within the facility. While this type of transmission remains uncommon, it represented an important shift in scientific understanding and highlighted the virus’s capacity to adapt in mammalian hosts.
Marine mammals have experienced some of the most devastating impacts. Since 2023, outbreaks have affected seals, sea lions, dolphins, porpoises and southern elephant seals across parts of South America and Antarctica. In Argentina, more than 95 per cent of southern elephant seal pups at one breeding colony died during a single outbreak, while tens of thousands of sea lions have also been lost across the region. These unprecedented mortality events demonstrate that H5N1 can have profound conservation consequences when it reaches susceptible mammal populations.
Taken together, these outbreaks have fundamentally changed our understanding of H5N1. What was once considered primarily a disease of birds is now recognised as a significant wildlife disease capable of infecting a remarkably diverse range of mammals under the right circumstances. While the level of risk varies between species, the international experience explains why conservation scientists are paying much closer attention to mammals than they were only a few years ago.
Which Australian Mammals Could Be Most at Risk?
Not all Australian mammals face the same level of risk from H5N1. The concern is not simply whether a species is native, threatened or well known. It is whether its behaviour could bring it into contact with infected birds, contaminated environments, or infected carcasses. Wildlife Health Australia identifies predatory and scavenging mammals, along with marine mammals that have close contact with seabirds, as the mammal groups most likely to be exposed.
The species below are presented according to the strength of the current evidence, drawing on overseas outbreaks, Australian wildlife guidance and each species’ ecology. Wildlife Health Australia specifically notes that predatory and scavenging marsupials, including Tasmanian devils, are expected to be at greater risk than plant eating marsupials such as wallabies and kangaroos. This distinction recognises that vulnerability varies between species and that exposure depends largely on feeding behaviour, habitat and ecology.
Tasmanian Devil
The Tasmanian Devil is Australia’s largest carnivorous marsupial and one of its most efficient scavengers. Although capable hunters, devils readily feed on carrion, consuming the carcasses of mammals and birds that would otherwise remain in the environment. That feeding behaviour makes them particularly relevant to discussions about H5N1 because scavenging infected birds is one of the most well documented pathways by which mammals have become infected overseas. Wildlife Health Australia also identifies Tasmanian Devils as an example of a predatory or scavenging marsupial expected to face a higher risk of exposure than herbivorous marsupials.
The pathway for exposure is straightforward. If infected seabirds were to die along coastlines, around breeding colonies or at inland wetlands, Tasmanian Devils could encounter the virus while feeding on carcasses. This is consistent with patterns documented overseas, where H5N1 infections in mammals have frequently been associated with scavenging or predation of infected birds. A recent Australian review of scavenger ecology also concluded that animals feeding on infected carcasses may face particularly high exposure because bird carcasses can contain large amounts of virus.
The conservation implications extend beyond feeding behaviour alone. Tasmanian devils remain listed as Endangered and continue to recover from the impacts of devil facial tumour disease (DFTD), which caused dramatic population declines across much of Tasmania. While H5N1 is a completely different disease, the arrival of any novel pathogen raises additional concerns for a species that has already experienced significant population loss. University of Sydney conservation biologist Carolyn Hogg has noted that “low immune diversity” becomes an important consideration whenever a new disease enters a population, while University of Tasmania immunologist Andy Flies has highlighted that some immune gene diversity may already have been reduced through the prolonged evolutionary and population impacts of devil facial tumour disease (DFTD).
None of this means Tasmanian Devils are expected to experience the same disease dynamics seen with devil facial tumour disease, nor does it mean H5N1 infection is inevitable. Rather, their scavenging ecology, threatened conservation status and existing disease pressures combine to make them one of the Australian mammals likely to remain a high priority for surveillance as H5N1 continues to circulate in Australian wild birds.
To learn more about the biology, conservation and recovery of this remarkable species, read our comprehensive guide to the Tasmanian Devil.
Quolls
Quolls occupy a similar ecological niche to Tasmanian Devils, although on a smaller scale. Both the Eastern Quoll and Spotted-tail Quoll are carnivorous marsupials that hunt live prey and will also scavenge carrion when the opportunity arises. That feeding behaviour places them within the same broad exposure pathway identified for mammals that consume infected birds or carcasses.
Unlike Tasmanian devils, there is currently very little evidence describing how H5N1 would affect quolls if they became infected. The absence of evidence should not be mistaken for evidence of safety. As Wildlife Health Australia national coordinator Dr Tiggy Grillo has said, “the other species that could be at risk in Australia are the ones that scavenge on birds or eat birds”.
That precautionary approach is already being reflected in conservation programs across Australia. Federal preparedness funding has supported planning for several threatened marsupials, including Western and Eastern Quolls. In Western Australia, planning has focused on the vulnerable Western Quoll, or Chuditch, while conservation managers at Mulligans Flat in the Australian Capital Territory are preparing contingency measures for reintroduced Eastern Quolls should H5N1 move closer to the region.
For now, quolls remain a species of interest rather than a species known to be highly susceptible. Their inclusion in H5N1 preparedness reflects their feeding ecology, threatened status and the recognition by Australian scientists that protecting vulnerable marsupials is far more effective before disease becomes widespread than after it has become established.
Australian Fur Seal
Australian Fur Seals are among the native mammals most likely to be discussed in relation to H5N1 because marine mammals have experienced some of the largest wildlife mortality events recorded during the current global outbreak. Wildlife Health Australia identifies seals and sea lions that live in close association with seabirds as mammal groups likely to face a higher risk of exposure. Overseas, H5N1 has caused major mortality events in seals, sea lions and elephant seals, particularly in South America, making Australian Fur Seals an important focus of surveillance and preparedness.
The concern is based on both ecology and international experience. Australian Fur Seals breed in dense colonies, haul out on rocky islands and coastlines, and regularly share habitat with large numbers of seabirds. Overseas, similar ecological conditions have been associated with extensive H5N1 outbreaks in pinnipeds, particularly in South America, where the virus caused unprecedented mortality among seals, sea lions and southern elephant seals. These outbreaks demonstrated that marine mammals can experience substantial impacts once H5N1 becomes established in coastal ecosystems.
Australia has already begun preparing for that possibility. As part of the national H5 bird flu preparedness program, the Australian Government has funded species specific preparedness planning that includes Australian and New Zealand fur seals in New South Wales. This reflects a precautionary approach based on the international evidence rather than any indication that Australian Fur Seals are currently affected.
To date, there have been no confirmed cases of H5N1 in Australian Fur Seals. Nevertheless, their colonial breeding behaviour, close association with seabirds and the experience of related species overseas make them an important focus of surveillance and preparedness planning.
Australian Sea Lion
The Australian Sea Lion is one of Australia’s most vulnerable marine mammals. Endemic to Australia, the species breeds only along the coastlines of South Australia and Western Australia, with an estimated population of about 11,200 individuals distributed across 67 breeding colonies. Many of these colonies are small and isolated, and the species has one of the slowest reproductive rates of any pinniped in the world.
Those life history characteristics make recovery from any major mortality event particularly difficult. Female Australian Sea Lions show strong fidelity to their breeding colonies, and populations are often genetically distinct. Localised disease outbreaks therefore have the potential to affect individual colonies for many years, particularly where pup production is already low.
International experience has highlighted why marine mammals are receiving such close attention. H5N1 has caused unprecedented mortality in closely related pinnipeds, including South American sea lions and southern elephant seals, with some breeding colonies suffering catastrophic losses. Wildlife Health Australia national coordinator Dr Tiggy Grillo has said that marine mammals are “really the ones in the firing line”, specifically identifying seals and sea lions as species of concern should H5N1 become established in Australian wildlife. Conservation organisations, including the Biodiversity Council, the Invasive Species Council and the Australian Marine Conservation Society, have echoed those concerns. Campaign director Alexia Wellbelove said bird flu poses “a real risk to the future of the Australian sea lion”, warning that overseas experience demonstrates the potential for the virus to be catastrophic for Australia’s unique wildlife and threatened species.
Australian governments have already incorporated these concerns into national preparedness planning. H5 bird flu funding announced in 2025 included targeted work to protect high risk native wildlife, with Australian Sea Lions specifically identified as a priority species. Additional conservation programs are also improving pup survival at important breeding sites such as Seal Bay, strengthening populations before any potential disease incursion. While there is currently no evidence that H5N1 has affected Australian Sea Lions, their conservation status, breeding biology and the experience of closely related species overseas make them one of Australia’s highest priority marine mammals for surveillance and preparedness.
Other Australian Mammals
While H5N1 has been confirmed in a wide range of mammals overseas, there is currently little evidence to suggest that all Australian mammals face the same level of risk. Wildlife Health Australia advises that predatory and scavenging mammals, along with marine mammals that live in close association with seabirds, are currently considered the most likely groups to be exposed. In contrast, herbivorous marsupials are expected to face a lower risk because they are less likely to encounter infected birds or carcasses.
The evidence also remains limited for other mammal groups. Wildlife Health Australia notes that no H5 bird flu infections have been reported in bats overseas, while only a small number of rodent species have been affected globally. As our understanding of H5N1 continues to evolve, surveillance across Australia’s wildlife will remain important. Based on the evidence available today, however, conservation efforts are appropriately focused on those mammals whose ecology creates the clearest pathways for exposure.
Why Tasmania Faces Unique Challenges
No part of Australia is immune to the movement of migratory birds, and there is currently no evidence that Tasmania faces a greater likelihood of H5N1 arriving than other parts of the country. However, Tasmania’s wildlife is unlike that found anywhere else in Australia, meaning the conservation consequences of H5N1 reaching the island’s native mammals could be particularly significant.
Tasmania is home to the world’s last remaining assemblage of carnivorous marsupials, including the Tasmanian Devil, Eastern Quoll and Spotted-tail Quoll. These species occupy ecological roles that have largely disappeared from mainland Australia. Tasmanian Devils, in particular, are highly efficient scavengers, while both quoll species also consume carrion as part of their diet. Wildlife Health Australia has identified predatory and scavenging marsupials as among the mammal groups most likely to be exposed to H5N1 through infected birds or carcasses.
The island is also internationally important for seabirds. Tasmania supports globally significant breeding colonies of shearwaters, albatrosses, penguins, petrels and other seabirds, while its coastlines provide feeding and resting habitat for migratory shorebirds travelling along the East Asian Australasian Flyway (EAAF). Every year, millions of birds move through this network, linking Tasmania to breeding and wintering grounds across the Asia Pacific region. These migrations are a natural part of healthy ecosystems, but they also illustrate how wildlife diseases can move across continents.
Bass Strait forms another important part of this ecological network. Although Bass Strait separates Tasmania from mainland Australia, it also forms an important ecological corridor through the regular movement of birds between breeding, feeding and migratory sites. Many seabirds and shorebirds routinely cross Bass Strait, while others move between Tasmania’s offshore islands and the mainland throughout the year. Understanding these natural movements is an important part of Australia’s H5N1 surveillance and preparedness efforts.
Tasmania’s island ecosystems also contain a high proportion of endemic wildlife found nowhere else on Earth. Many native mammals already face significant conservation pressures, including habitat loss, road mortality and, in the case of the Tasmanian Devil, the continuing impacts of devil facial tumour disease. The arrival of any new wildlife disease has the potential to place additional pressure on species that are already the focus of long term conservation and recovery programs.
For these reasons, Tasmania remains an important focus of H5N1 preparedness. The concern is not that widespread impacts on native mammals are inevitable, but that the island’s unique wildlife makes preparedness one of the most important conservation tools available. Continued surveillance, strong biosecurity measures and a clear understanding of how the virus could affect native species will help ensure Tasmania is well prepared as H5N1 continues to be monitored across Australian wild birds.
What Heard Island Taught Us
For many Australians, H5N1 became real when it reached Heard Island and McDonald Islands. These remote Australian territories lie deep in the Southern Ocean, thousands of kilometres from the mainland, and support internationally significant populations of seabirds and marine mammals. Although isolated, they form part of Australia’s unique natural heritage and provide an important window into how H5N1 behaves in remote wildlife ecosystems.
The outbreak on Heard Island demonstrated that H5N1 was capable of causing widespread mortality in the kinds of coastal ecosystems found throughout the Southern Hemisphere. It affected seabirds and marine mammals living in dense breeding colonies, reinforcing patterns that had already been observed in South America. For Australian conservationists, the significance was not simply where the virus had been detected, but what it revealed about the species and habitats most vulnerable to its impacts.
The importance of Heard Island became even clearer when genomic sequencing showed that the H5N1 virus detected in a Brown Skua in Western Australia was closely related to the virus responsible for the Heard Island outbreak. While this did not necessarily indicate direct movement between the two locations, it confirmed that the virus detected on mainland Australia belonged to the same broader lineage already circulating within Australian territory. That finding reinforced the value of Australia’s surveillance systems while highlighting the interconnected nature of migratory wildlife and marine ecosystems.
The Heard Island outbreak also shifted the conversation from biosecurity to conservation. Although protecting poultry and agricultural industries remains an important part of Australia’s H5N1 response, the impacts on wild seabirds and marine mammals demonstrated that the virus is also a significant wildlife conservation issue. For threatened native mammals such as Australian Sea Lions and Tasmanian Devils, understanding these international patterns remains an important part of preparedness and long term conservation planning.
How Wildlife Rescue is Preparing
For wildlife rescuers and rehabilitation hospitals, H5N1 changes more than the way sick animals are treated. It changes the first decision made at the point of rescue. In ordinary circumstances, an injured wild animal may be contained, transported and admitted for assessment. With suspected H5N1, the priority becomes preventing further spread, protecting people, and avoiding exposure to other animals already in care.
Wildlife Health Australia advises that suspected cases in wildlife should be approached with an “avoid, record, report” response. Members of the public and wildlife volunteers are advised not to touch sick or dead wildlife, to observe from a distance where safe, record the location and details, and report unusual sickness or deaths through the Emergency Animal Disease Hotline. The same principle applies to wildlife hospitals: suspected H5N1 cases are not simply treated as ordinary admissions.
Wildlife hospitals and rehabilitation facilities have had to adapt their response procedures. Rather than admitting every sick bird or mammal presented to them, suspected H5N1 cases are generally referred to the relevant government authorities in accordance with established emergency animal disease protocols. This approach helps ensure potentially infected animals are managed safely while reducing the risk of exposing veterinary staff, volunteers and other wildlife undergoing rehabilitation.
That distinction matters. Wildlife hospitals often care for many animals at once, including orphaned joeys, injured birds, reptiles, possums and threatened species. Bringing a suspected H5N1 case into that environment could risk exposing vulnerable animals, volunteers and veterinary teams. Changing admission protocols is therefore not a lack of care. It is a biosecurity measure designed to protect both wildlife and the people caring for them.
Personal protective equipment also becomes more important. Wildlife Health Australia and government guidance emphasise that sick or dead birds and other suspect wildlife should only be handled by people with appropriate training, equipment and authorisation. For wildlife carers, this may mean masks, gloves, eye protection, disposable coveralls, careful cleaning and disinfection, and clear procedures for transporting, isolating or reporting animals. These measures help protect people while reducing the risk of the virus being inadvertently carried between animals, facilities or locations.
For rescue groups, preparation is not only about equipment. It is also about decision making. Volunteers need to know which species and symptoms require reporting, when not to attend a rescue, who to call, and how to keep themselves, their vehicles and their homes safe. In many cases, the most responsible response to a suspected H5N1 case will be to step back, record information, and let biosecurity authorities take over.
This can be emotionally difficult for people who are used to helping wildlife directly. Wildlife rescue is built on action: answering the phone, driving to the animal, bringing it into care and giving it the best possible chance. H5N1 sometimes requires a different kind of care. It asks rescuers to protect the wider wildlife population by recognising when an animal should not be moved, handled or admitted.
In that sense, H5N1 preparedness is part of wildlife conservation. Strong biosecurity protocols help protect wildlife hospitals, carers and the animals already in rehabilitation. They also help ensure suspected cases are identified, reported promptly, investigated appropriately and managed by the authorities responsible for Australia’s emergency animal disease response.
If you encounter sick, injured or orphaned wildlife, knowing what to do first can make all the difference. Our guide to What to Do If You Find Injured Wildlife explains the safest way to respond.
What Should the Public Do?
If you see sick, injured or dead wild birds, or unusual deaths involving multiple birds or marine mammals, do not handle them unless instructed to do so by the relevant authorities. While most sick or dead wildlife will not have H5N1, it is important not to assume the cause or risk unnecessary exposure.
Instead, observe the animal from a safe distance and, where possible, record its location, the species involved and any obvious signs of illness or injury. If it is safe to do so, photographs can also assist authorities with their assessment. Suspected cases should be reported through the Emergency Animal Disease Hotline on 1800 675 888, or to your relevant state or territory wildlife authority.
If you are walking dogs, avoid allowing them to investigate or scavenge sick or dead birds, particularly around beaches, wetlands and waterways where waterbirds and seabirds gather. Keeping pets under effective control helps reduce the risk of disease exposure while also protecting native wildlife.
Most importantly, H5N1 preparedness is based on early detection rather than fear. Prompt reporting helps authorities investigate unusual wildlife deaths, monitor the spread of disease and respond quickly when needed. Public awareness, responsible reporting and following official advice remain among the most valuable contributions anyone can make to protecting Australia’s wildlife.
Why Preparation Matters
H5N1 has changed the way scientists think about avian influenza. Once regarded primarily as a disease of birds and poultry, the virus has demonstrated an unprecedented ability to affect wild mammals around the world. Although Australia has now confirmed H5N1 in wild birds across multiple states, the catastrophic wildlife mortality seen overseas has highlighted why preparation remains just as important as response.
For Australia’s native mammals, preparedness is not based on fear or assumptions. It is based on understanding ecology, identifying species that may be more likely to encounter the virus, strengthening surveillance, and ensuring wildlife carers, veterinarians and government agencies are ready to respond if needed. The goal is not to predict what will happen, but to reduce uncertainty through good science, careful planning and early action.
For Tasmania, that preparation carries particular significance. The island is home to unique carnivorous marsupials found nowhere else on Earth, while Australia’s marine mammals include species already facing significant conservation challenges. Protecting these animals means learning from what has happened overseas, recognising the pathways by which H5N1 can spread, and applying that knowledge before disease affects vulnerable wildlife populations.
Ultimately, conservation is at its strongest when it is proactive rather than reactive. Monitoring wildlife, supporting disease surveillance, investing in research and responding quickly to emerging threats all help build healthier, more resilient ecosystems. Whatever the long term impacts of H5N1 in Australia, the work being done today will strengthen our ability to protect the wildlife that makes this country unique.
To follow the outbreak as it unfolds, see our H5N1 Bird Flu Australia Timeline. For an overview of H5N1 in Australia, read our H5N1 Bird Flu in Australia article.
Editorial Note: Wild Island is committed to publishing accurate, evidence based wildlife information. This article has been researched using authoritative sources, including government agencies, scientific institutions and peer reviewed literature. The information in this article was verified at the time of publication and will be updated if significant new evidence or guidance becomes available.
Leave a Reply