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Australian rodent thought to be extinct is found alive on desert island
Gould's field mouse, a small rodent native to Australia, is not extinct as previously thought. It is alive and well living under a different name.
Genetic analysis of museum specimens has solved the case of double identity. It has revealed that the Gould's field mouse (Pseudomys gouldii), once found across much of mainland Australia but last seen in 1857, is physically and genetically identical to the djoongari, also called the Shark Bay mouse (Pseudomys fieldi), which is currently known only to exist on three islands in Shark Bay, Western Australia.
It's good news, as little is known about this rodent that was once prevalent across Australia but rapidily went extinct after European arrival.
The djoongari is a social, rotund rodent. They are omnivores and eat most things including insects, fungi, flowers and leaves. Djoongari build burrows but also like to nest and tunnel under vegetation and seaweed. They live in family groups © Wayne Lawler and Australian Wildlife Conservancy
The species will still be known by the common name djoongari, or Shark Bay mouse, while reverting to the original scientific name Pseudomys gouldii.
Dr Roberto Portela Miguez is the Senior Curator of Mammals at the Museum and who was involved with the study, says, 'It's exciting to see the taxonomic revival of this species but even better to know that there are animals of this species still left in the wild'.
There are many rodents native to Australia, including the dusky hopping mouse and the greater stick-nest rat.
Rodents make up 41% of all Australian mammals to go extinct since European arrival in 1788. To understand their decline, researchers looked at the genomic data from eight extinct Australian rodent species and 42 living rodent species.
Museum collections and species' conservation
The genetic information for the study came from museum specimens stored in collections all over the world, including the Natural History Museum and Melbourne Museum. Some of the specimens examined were over 180 years old.
'There are only a few specimens of the Gould's field mouse kept in museums and it's fantastic that we can get meaningful genetic information from them given they are so old,' explains Roberto. 'One Gould's field mouse specimen in the Museum was collected in 1837.
'The type specimen in the Natural History Museum has a damaged skull so it is difficult to compare to other modern specimens. The only way to know if the specimen is the same species or a different one is to do a genetic analysis.
'This study reveals the potential of museum collections to enlighten us about ecosystems and understand the impact we have on them. Hopefully this work will help inform conservation and land management.'
The skin of the djoongari type specimen held in the Museum, image by C.Ching courtesy of the Trustees of the Natural History Museum, London
Why did the djoongari disappear from mainland Australia?
The djoongari was once a very successful animal and was found across Australia from south-west Western Australia across to New South Wales.
Dr Emily Roycroft, from the Australian National University and one of the lead authors of the paper, says, 'The introduction of feral cats, foxes and other invasive species, agricultural land clearing and new diseases absolutely decimated native species that were otherwise relatively stable and potentially had quite large population sizes.'
Other threats include inappropriate fire management and climate change. Some rodents were also intensely hunted for bounty in the late ninetieth and early twentieth centuries.
The remaining populations of the djoongari were found on a single 42 km2 island in Shark Bay, Bernier Island. One small population is not enough for a species to survive, so they have been taken to two other islands to establish new populations.
© Wayne Lawler and Australian Wildlife Conservancy
The juicier you are, the more likely you are to go extinct
This study also shows that having a slightly larger body size places rodents under a greater risk of predation and therefore a greater risk of extinction.
Those rodents that have become extinct since the arrival of Europeans weighed above 90 grams and the rodents that are still alive tend to be under 50 grams.
The loss of these species is likely to have wide-ranging impacts, as the importance of rodents in an ecosystem cannot be underestimated.
'Rodents have the greatest number of species of all the mammals. They are great ecosystem engineers as they are predators of plants, fungi and invertebrates. They are also important in the food chain for the many species prey on them,' says Roberto. 'The more we understand them, the more we can protect them and the ecosystems they live in.'
'Understanding rodent diversity is challenging, in part because some species could be hard to tell apart, but advances in DNA techniques have opened a world of possibilities for historical collections to help us with this task.'
Vegetation grows on the dunes of Shark Bay Australia. Djoongari are social creatures that nest and tunnel under vegetation and seaweed © Mark Ditcham/Shutterstock
