Monitoring toad-smart quolls at East Alligator

A family of quolls captured by a motion detection camera in Kakadu National Park | Image credit Department of Land Resource Management

The northern quoll is a small marsupial predator that was once abundant in Kakadu.

Sadly, after cane toads arrived in the park in 2003 we saw quoll numbers decline. Adult cane toads are highly toxic, and possess large skin glands brimming with a cocktail of deadly chemicals. Quolls that attack or mouth adult cane toads often ingest a fatal dose of toxins, and they rapidly go into convulsions and die while the toads hop away unharmed.

Northern quoll | Image credit Jonathan Webb

It will be hard to eradicate cane toads from Kakadu, so introducing ‘toad-smart’ quolls to the park is one solution to help quolls in their fight against the toad. How do you make quolls toad-smart? Well, the method I developed is deceptively simple: just make the quolls sick! Working with staff from the Territory Wildlife Park, my colleagues and I trained captive reared quolls not to eat cane toads by feeding them a small dead toad coated with an odorless, tasteless nausea-inducing chemical. Quolls that ate the toads became mildly ill, and subsequently, they associated the smell of toads with illness, and refused to attack live toads. Anyone who has had food poisoning will understand how this works; just the mere sight or smell of the food that made you ill can make you feel queasy, and this feeling can produce long-term food aversions. Importantly, we discovered that toad-smart quolls also develop long-term aversions to cane toads.

Cane toads | Image credit Jonathan Webb

Spurred on by these encouraging results, in December 2009 and February 2010, we reintroduced 50 toad-smart quolls (22 females, 28 males) to East Alligator Ranger station. PhD student Teigan Cremona monitored this population over four years and radio-tracked adult females and their offspring. Teigan discovered that each generation of quolls learns to avoid cane toads. Just like humans, juvenile quolls that have left home often dine with their mothers, and this extended period of maternal care gives juveniles a chance to learn that toads are off the menu.

Encouragingly, the quoll population at East Alligator has increased since the reintroduction.

PhD student Teigan Cremona | Photo credit Rodney Cremona

Dr Jonathan Webb, University of Technology Sydney

This research was supported financially by grants from the Australian Government’s National Environmental Research Program (NERP), the Mazda Foundation, the National Geographic Conservation Trust, the Caring for Our Country scheme, and the Australian Research Council. We appreciate all the support provided by the traditional owners of Kakadu, the staff from Kakadu, and all of the volunteers who have helped with fieldwork over the last five years.