The tale (or tail) of an extraordinary marsupial

Research's blog | Created 4 years ago

 

Author:
Dr Kenny J. Travouillon
24 August 2020

Is it horse-footed or pig-footed?

The Pig-footed Bandicoot is one of the oddest marsupials that has ever lived. It is unfortunately now extinct, but we still have museum specimens and several accounts written by early naturalists giving us an idea of what it was like. It is unique in walking on two toes on its front feet like a pig, and one toe on its back feet like a horse. Its legs were long and thin allowing it to gallop like a miniature horse at legendary speeds to escape its predators. It fed predominately on grass and weighing only about 500 grams (twice the size of a rat), it was one of the smallest grazing mammals known.   

European names

Aboriginal people have been living alongside the Pig-footed Bandicoot for over 60,000 years. Most aboriginal languages have a name for this animal. When Europeans first arrived in Australia, they were amazed by diversity and uniqueness of its fauna. The Pig-footed Bandicoot was first seen by Europeans during Major Mitchell’s journey through central New South Wales in the 1830s. He collected an animal which was later sent to the Australian Museum in Sydney, but a drawing of the animal which he sent to Mr Ogilby in England triggered its naming in 1838. The illustration showed an animal that resembled a bandicoot but with long ears, two toes on its feet, and no tail. He coined the scientific name Chaeropus ecaudatus, which means ‘pig foot without tail’. A few years later, a skin and skeleton of a Pig-footed Bandicoot from South Australia arrived in England, and the famous biologist at the British Museum, Mr Gray, noticed that the animal had a tail and he quickly published this discovery and even tried to rename the species Chaeropus castanotus. Meanwhile, Mr Gilbert in Western Australia sent another Pig-footed Bandicoot specimen to Mr Gould in England, who then named it as a new species, Chaeropus occidentalis (meaning western pig foot) in his book ‘Mammals of Australia’. This second species name didn’t last, with scientists suggesting that it was no different to the first species, and so only one species remained, Chaeropus ecaudatus.  

My story

This is where my story really begins. While undertaking research on fossil bandicoots and bilbies, I visited the Australian Museum to examine any Pig-footed Bandicoot specimens. I needed to compare features of the skull with the fossils to work out how they were related. I also found that the website of Museum Victoria contained some images of a Pig-footed Bandicoot skull in their collection. However, I was perplexed that the Museum Victoria skull collected from Central Australia was slightly different to the skull at the Australian Museum. Skull differences in mammals are usually good evidence of speciation so I investigated further. Unfortunately, with as few as 29 museum specimens in existence, scattered all over the world, it was not going to be an easy task. My luck changed when I received a Churchill Fellowship, followed by an ABRS grant (Australian Biological Resources Study). Thanks to the Churchill Trust and the ABRS who funded my 2-month journey across the world and then trips across Australia, I was able to visit all museums that had specimens of Pig-footed Bandicoots.  

21^st Century discovery                           

My study of the skins and skulls in museums allowed me to quickly find differences between the specimens collected in southern Australia and central Australia, confirming that they were different species. There were also differences within the southern species between east and west, which allowed the recognition of two subspecies, Chaeropus ecaudatus ecaudatus in the east, and Chaeropus ecaudatus occidentalis in the west. To further test the theory there were two species of pig-footed bandicoots, I needed to undertake analysis of their DNA. Professor Michael Westerman at La Trobe University had already retrieved DNA from a specimen collected from central Australia preserved in Museum Victoria.

Meanwhile, when I contacted the Natural History Museum in London to arrange my trip, I told them about my project and Roberto Portela Miguez, the mammal collection manager, told me that he had been working with Bruno Simões and Selina Brace (both working in the DNA lab of the museum) on retrieving DNA from the two specimens in their collection. Bruno immediately sent me their data, and luckily, the two specimens were from the southern species. We were then able to compare the DNA of the northern and southern populations, and the results confirmed that there were indeed two distinct species.

The next step was to name the new species. The southern species already had a name, Chaeropus ecaudatus, but the central Australian species did not. We wanted to honour traditional owners of the land where this species came from, so we chose the name Chaeropus yirratji. ‘Yirratji’ is the name of this species in the aboriginal language of the Alice Springs area.

More detective work

Now that both species had names, it was time to untangle their ecology. Both being extinct, it’s not easy to know what they were like when they were alive. However, the museum specimens were able to provide tantalising clues, along with contemporary articles published in scientific journals and newspapers. The teeth of the museum specimens indicated that the Yirratji had teeth better suited to eating grass than the southern species. An earlier study from a dissected museum specimen had also found only grass in its stomach.  

Reconstructing the distribution of the two species across Australia was another challenge. Along with the 29 museum specimens, we examined fossils and subfossils in palaeontology collections which helped fill the distributional gaps, allowing use to establish that the Yirratji mainly occurred in sandy deserts, whereas the southern pig-footed bandicoot preferred woodlands.

With their distribution mapped, it was much easier to tackle the next question: when did they become extinct? Previous researchers had established that newspaper accounts had sometimes recorded the last sighting of the species in an area, and some had interviewed traditional owners to learn if they recall seeing the animal. My colleague at the South Australian Museum, David Stemmer, looked into museum archives to find more information about the last specimens ever collected. We established that Chaeropus ecaudatus went extinct between 1910 and 1920, probably as a result of land clearing for developing agriculture across southern Australia, and the arrival of the European Fox, which spread from east to west, killing off the remaining individuals. Chaeropus yirratji survived much longer, until the 1950s, probably because it took longer for the fox to venture into more arid environments.     

Major Mitchell’s specimen and a new Neotype

Major Mitchell collected the first specimen of Chaeropus ecaudatus which he sent to the Australian Museum. The Australian Museum had on record that only a skull of the animal was received. However, my colleague, Dr Sandy Ingleby, who manages the collection, informed me that the specimen in the Australian Museum was a skull and a skeleton, and the skeleton had a tail. We know for a fact that Major Mitchell’s specimen didn’t have a tail, so this specimen wasn’t the one he collected. When a species is named, the specimen that is used to name that species is called a holotype, and this specimen is kept in a museum so others can use it to compare with any other specimen and work out if they have a new species or not. If a holotype is lost or accidentally destroyed (e.g. fire), it is important to replace it by designating a new specimen, which is then called the neotype.

Australian Museum scientist Dr Harry Parnaby, had researched the history of the collection in great detail. Working together, we were able to show that Major Mitchell’s specimen – the holotype – went missing soon after 1874. As a result, we selected the only skeleton at the Australian Museum as the neotype, to replace it.

Never forgotten

Discovering and documenting a new species almost 70 years after it went extinct is rather sad, but at least it won’t be completely forgotten. Museum collections play a very important role in species discoveries, and there are many more awaiting to be discovered. The extinction of two pig-footed bandicoot species can teach us a lesson that we must care for our fauna otherwise it will be gone forever, and only remembered in museum displays. Very few museums have pig-footed bandicoots on display: the first Yirratji specimen (Chaeropus yirratji) to be collected is on display in the museum in Paris, another Yirratji on display at the South Australian Museum, a Southern Pig-footed Bandicoot (Chaeropus ecaudatus) at Museum Victoria, and subfossils of both species will be going on display in the Western Australian Museum, opening on 21 November 2020.