What's That Smell? How Marsupials in Mulligans Flat Respond to Different Predator Odours

Abstract

Approximately 10% of native Australian mammals have become extinct in the time since European settlement, with introduced predators being a main contributor to that loss. Predator free reserves act as refuges, or ‘islands’, for vulnerable species and are regularly used for reintroductions. Reintroductions outside of these areas often fail due to prey naïveté, which can include the inability to recognise the odours of predators. Different prey species use landscapes in a variety of ways, and spend more time in areas which they perceive to be less risky as per the ‘landscape of fear’ concept. I set out to test how resident marsupials and reintroduced marsupials in a reserve free of mammalian predators responded to a range of predator odour cues. I also tested whether odour on its own, or an interaction with vegetation cover, influenced prey animals’ behaviour. I used material treated with body odours of rabbits, foxes, cats, dingoes and thylacine, and placed them in sites characterised by either low or high vegetation cover. Using camera traps, I measured the number of visits by different marsupial species to these sites, the duration of each visit, and the duration of vigilance behaviour compared to control sites with no odour. I found that vegetation cover played a large role in how marsupial prey responded to odours. Eastern bettongs avoided sites with low vegetation cover and spent less time in the sites with rabbit odour, perhaps to avoid perceived competition. Eastern bettongs also displayed an increase in vigilance behaviour at sites with dingo odour in low and high vegetation cover. Eastern bettongs, eastern grey kangaroos, and brushtail possums all displayed anti-predator behaviour at sites with cat odour in high vegetation cover by displaying increased vigilance. Eastern grey kangaroos and brushtail possums displayed anti-predator behaviour to thylacine odour. Brushtail possums reduced the time spent at sites with fox odour. My study demonstrates that these marsupials can, to some degree, respond to novel predators after a period of isolation. My results also demonstrate the importance of considering vegetation cover and the ‘landscape of fear’ concept when undertaking olfactory recognition studies. The next step in this research is to understand how marsupial species respond to predators’ odours outside of a predator-free area. This might involve a comparative study that observes species behaviours inside and outside of a fenced reserve. Research to look at volatile chemicals within predator body odour may help explain responses to introduced predators. My research has contributed to the understanding of predator-prey interactions between native marsupials and their potential predators, and has demonstrated all the species studied showed at least some level of naïveté which could be detrimental to them outside Mulligans Flat Woodland Sanctuary. However, further research using an experimental reintroduction to a site with low numbers of predators may allow prey to gain exposure and quickly adapt to the environment.