Eastern quolls – in a spot of bother?
Eastern quolls are one of Tasmania’s most charismatic species – a beautifully patterned marsupial carnivore that comes in shades of both fawn and black. Indeed, they’re a species that we’re lucky to still have roaming around, having gone extinct on mainland Australia during the last century – a result of a combination of persecution, disease and the unrelenting pressure of feral predators like cats and foxes.
However, a recent study by researchers from the University of Tasmania (Cunningham et al. 2022) in the journal Australian Mammalogy, has highlighted their vulnerability even within their Tasmanian refuge.
Eastern quolls experienced rapid declines across Tasmania in the early 2000s, likely as a result of a prolonged period of unsuitable weather. To investigate these declines further, Cunningham’s study used information collected by the Tasmanian Government during annual spotlighting surveys that have been conducted across the island since 1975. These surveys represent an extremely valuable long-term dataset to investigate trends in Tasmanian wildlife – for example, they have previously been used to help quantify disease-induced declines in Tasmanian devil populations since the 1990s.
Here, the data reveals that eastern quoll numbers across Tasmania have continued to fall since the turn of the century. The average number of quolls recorded on each spotlighting transect has fallen from a high in the mid-90s of around 1 quoll sighted for every 2 x 10km transects driven, to a recent low of less than 1 out of every 5 transects resulting in a quoll sighting.
These kinds of numbers just won’t sound right to many Tasmanian residents, with eastern quolls currently a common sight in quite a few well-populated parts of Tasmania, like the Huon Valley or North Bruny Island. However, these high numbers in places where the quolls are most visible are masking declines in other areas. The overall declines have been extremely uneven in terms of where they occur, with populations like those highlighted above recovering well from the turn of the century decline, whilst others have struggled to recover, or fallen even further. Places that used to be strongholds for the species, such as the east coast and the Central Highlands, have seen huge declines in sightings, with no signs of recovery apparent.
This pattern is hugely concerning, as while the turn of the century falls seem to have been attributable to weather conditions, the reasons behind the more recent slides are much less readily apparent. Multiple factors are likely at play, from a shifting climate, to habitat degradation, to the impact of feral cats being exacerbated by Tasmanian devil declines.
The bottom line is, to appropriately manage eastern quoll populations into the future and help stave off further declines, we need to better understand what’s driving them. Ongoing work by the TLC and our research partners will address some of these knowledge gaps and help us secure the future of eastern quolls in Tasmania.
So as not to end on a bum note, the TLC’s annual fauna monitoring at Five Rivers in the Central Highlands picked up increases in eastern quoll activity earlier this year. Just over half of our cameras picked up eastern quolls, with an overall increase in activity observed since last year’s monitoring. These are encouraging signs that the quolls had a good breeding season in 2021, which can only be a good thing!