Millions of people have a phobia of them and many more find them just plain revolting. They’ve been demonised more than a few times in popular culture – after all, J. K. Rowling certainly didn’t do them any favours with her character Scabbers. I’ve got to admit, for a long while I was among the people who scrunched up their faces at the idea of having to hold one. After doing some research though, my mind started to change – at least, for our Australian species. Rodents are the most abundant group of mammals on Earth, with over 2,700 species described within the group. Of these, more than 60 are found within Australia, across every state and territory.
While some people may recoil at the idea of so many different rodents found throughout the nation, how they got here is actually quite extraordinary. Australia became a separate land mass 50 million years ago, but rodents reached the continent much more recently. The first wave of rodents arrived between five to eight million years ago, and the second wave, which was almost solely species within the genus Rattus, came in the last one million years. Both these waves were aided by the rising and falling sea levels around the Indonesian Islands, which are believed to be the origin point for our native rodent species.
Since their introduction to Australia, rodents have dispersed and diversified in extraordinary ways. In the northern states of Australia, a group of mice called pebble-mound mice are the only mammals on earth that construct mounds of small stones around burrows. Hopping mice are another unique group of rodents that are only found in Australia, moving in a hopping motion very similar to our native marsupials, despite there being no close relation between the two groups. In the southern states, the New Holland mouse is a social species that is particularly resilient to fire, with its population often increasing after an event. As well as being highly unique, rodents often aid the ecosystems in which they’re found, with recent studies finding that many species are responsible for spreading mycorrhizal fungi, which is crucial to the survival of various trees within Queensland’s tropical rainforests.
If these species don’t fit in very well with what you imagine when you think ‘rodent’, it’s most likely because the images we typically have of rats and mice are actually invasive species. While the house mouse, black rat and brown rat are all found here, they were actually introduced by European settlers who brought them to Australia – and most of the world – on their ships. While Australian species can be carriers for disease, and it’s not advised for you to go and pick one up, it’s the invasive species that have been linked most closely to the spread of disease and infection.
Rodents make up about one quarter of Australia’s mammals, and are key parts of our environments and ecosystems – but unfortunately, despite their importance, they haven’t escaped the impact of their cousins’ reputations. Habitat destruction and predation from cats, dogs and foxes are major drivers for the decline of our native species. Despite this, funding for research and conservation for rodents is difficult to obtain, due to the stigma surrounding the words ‘mouse’ and ‘rat’. Since European settlement, half of our hopping mice species have gone extinct. Stick-nest rats, a group of rodents that construct their nests out of a variety of sticks and other plant material, are now extinct on mainland Australia. Many species, such as the smoky mouse, are being threatened by habitat destruction. As Australia’s human population increases, we continue to encroach on our native rodents and their habitats, often with devastating results. Since European settlement, an estimated 36% of native rodents have become extinct.
However, not all the news about our native rodents is bad. The water rat, also known as the rakali, has managed to recover after almost being driven to extinction. The species was nearly eradicated during the hunting trade of the 1930s and 1940s, and later in the 1950s due to people seeing it as a pest. Changes to permits as well as shifts in public attitudes have led to populations making a recovery. Similarly, the New Holland mouse was a species that was thought to have gone extinct for over 100 years, until its rediscovery in the 1960s in Sydney. Since then, conservation programs have been enforced to ensure that we don’t lose the species a second time around.
Approximately 91% of our rodent species are found nowhere else on Earth, and recent genetic work on some species indicates that the diversity may be even greater than what we can see taxonomically. But this diversity can only be preserved if we decide to protect and conserve these species. Like so many animals before them, rats and rodents are misunderstood – but we can change that misunderstanding, if we can just change our perception.
Cover image by Billy Geary.