Over the past 200 years Australia (along with Central America) is the country that has recorded the highest number of mammal species that have suffered major decline or extinction due to invasive predators, with the red fox and feral cat the most damaging. Globally, cats, rodents, dogs and pigs threaten the greatest numbers of endangered vertebrates (see reference 1 below).
A major reason that native animals are so vulnerable to introduced predators is thought to be their naivety – failure to recognise and defend themselves against the threat (see reference 2 below). Understanding how native prey respond to invasive predators can help protect vulnerable species.
Dr Anke Frank from the University of Tasmania, School of Biological Sciences, and fellow researchers from Macquarie University and University of Sydney surveyed Hobart residents to determine whether bandicoots avoid backyards that are home to domestic dogs and cats. They were seeking to inform the broader questions: do Tasmanian bandicoots fail to recognise dogs and cats as a threat because they were relatively recently introduced to Tasmania (around 200 years ago) and how can this knowledge assist their protection? (see reference 3 below).
Recently 548 residents in urban and peri-urban areas of Hobart completed a survey focusing on their backyards – sightings of bandicoots and their scats, presence of domestic cats and dogs and vegetation characteristics. Thirty-seven per cent of respondents owned at least one dog and 20% at least one cat (see reference 3 below).
While over 25 respondents reported that their pets had killed bandicoots, sightings of bandicoots or their scats were equally likely to be reported in backyards with or without domestic dogs or cats. The presence of these pets, regardless of their number or roaming behaviour, did not appear to influence the presence of bandicoots (see reference 3 below).
In contrast, the same study undertaken in peri-urban Sydney reported evidence that bandicoots avoided backyards with resident dogs, including where dogs were kept indoors at night. The presence or absence of domestic cats, however, had no impact on whether bandicoots visited the Sydney backyards (see reference 4 below).
The authors hypothesised that, even though dogs and cats were both introduced to Australia around 200 years ago, avoidance of Sydney backyards (but not Tasmanian backyards) where dogs lived may be due to mainland bandicoots’ long-term exposure to the dingo. The dingo is a close relative of the domestic dog and arrived on mainland Australia around 4000 years ago. This prolonged exposure may have resulted in bandicoots adapting over evolutionary time to avoid dogs. They also proposed that only 200 years of exposure to cats across Australia is insufficient for bandicoots to develop cat avoidance behaviour (see reference 3 and 4 below).
While these hypotheses needs further testing, this study has important implications for conservation. Bandicoot species have seriously declined across Australia. Of the two Tasmanian bandicoots, the southern brown bandicoot is a listed threatened species across most of its southern mainland range and the eastern-barred bandicoot across its entire Australian range. Introduced predators, including cats and dogs, along with habitat loss, are the major threats.
Notably, the study found that abundant vegetation shelter (especially native vegetation) in backyards and close proximity to bushland made the presence of bandicoots in backyards more likely (see reference 3 below). This confirms the importance of habitat/shelter for the protection of wildlife that has been found by many other Australian studies.
Dr Frank says:
"Keeping and expanding thick understory vegetation in backyards and bushland is one of the most effective ways to protect bandicoots in Tasmania. In addition, containing and controlling domestic dogs and cats is crucial. Preventing dogs and cats from roaming outside, at least between dusk and dawn when bandicoots are most active, and keeping dogs on leads, particularly in or near bushland areas is recommended."
Article and photos by Kaylene Allan - Kingborough Council Cat Management Officer
1. DohertyTS, GlenAS, NimmoDG, RitchieEG, DickmanCR(2016). Invasivepredatorsandglobalbiodiversityloss. ProceedingsoftheNationalAcademyofSciencesoftheUnitedStatesofAmerica 113: 11261–65.
2. Carthey AJR, Banks PB (2014). Naïveté in novel ecological interactions: lessons from theory and experimental evidence. Biological Reviews. doi:10.1111/brv.12087
3. Frank ASK, Carthey AJR, Banks PB (2016). Does Historical Coexistence with Dingoes Explain Current Avoidance of Domestic Dogs? Island Bandicoots Are Naïve to Dogs, unlike Their Mainland Counterparts. PLoS ONE 11(9): e0161447. doi:10.1371/journal.pone.0161447
4. Carthey AJR, and Banks PB (2012). When Does an Alien Become a Native Species? A Vulnerable Native Mammal Recognizes and Responds to Its Long-Term Alien Predator. PLoS ONE 7(2): e31804. doi:10.1371/journal.pone.0031804