The Tasmanian devil and the spotted-tailed quoll are well-known meat-eating marsupials, but Australia is home to many other carnivorous and insectivorous pouch mammals. Some of these marsupials are as small as a mouse or even smaller. Among them are the planigales, which are the tiniest of them all. Despite their small size, planigales are fierce predators that often take on prey as big as themselves.
Currently, there are four known species of planigale in Australia. However, recent discoveries have revealed two new species in the Pilbara region of northwest Western Australia: the orange-headed Pilbara planigale (Planigale kendricki) and the cracking-clay Pilbara planigale (P. tealei).
Planigales are named after their flat heads, which allow them to seek shelter in small cracks in rocks and clay soils. They are among Australia’s smallest mammals, with some weighing an average of 4-6 grams and measuring around 11cm in length, while others are slightly larger at 8-17 grams and 13cm long.
Previous scientific studies using body shape and DNA data have suggested that there may be more planigale species than currently known. To test these theories, scientists examined the planigales in the Pilbara region and found that they displayed unique body shapes and were genetically unrelated to any of the four known species.
The process of describing these two new species began over 20 years ago by scientists at the Western Australian Museum. They started their work after capturing planigales during surveys for mining development in the Pilbara that didn’t fit the descriptions of known species. These planigales were usually identified as either the common planigale or the long-tailed planigale due to lack of better options.
After examining specimens held in the WA Museum and sequencing their DNA, scientists confirmed the discovery of the two new species. Unfortunately, the lead taxonomist, Ken Aplin, fell ill and passed away in 2019. However, with support from the Australian Biological Resources Study and the Queensland University of Technology, the research was completed and the species descriptions were submitted for publication.
The orange-headed Pilbara planigale is the larger of the two new species, weighing an average of 7g (up to 12g for large males) with a longer, pointier snout and bright orange coloring on the head. The cracking-clay Pilbara planigale is much smaller, averaging just 4g with darker coloration and a shorter face. It has only been found on cracking clay soils.
Both species occur in the Pilbara and surrounding areas, requiring a dense cover of native grasses to survive. They are nocturnal and actively forage at night while seeking shelter during the day.
These discoveries also revealed that the common planigale and the long-tailed planigale do not occur in the Pilbara or on neighboring Barrow Island as previously believed. There is still more work to be done as there are two “species complexes” of planigales where genetic data suggests that a species is made up of multiple different forms. Further analysis will be conducted to define more of Australia’s tiniest mammals.