Courses I teach

I am Unit Executive Officer of the third year biology course BIOL3010 Tropical Wildlife Biology and Management. This course consists of a five day wildlife school which is held at Mary River Park, NT, in February each year, followed by lectures and practicals at the University of Sydney. Students from other Universities in Australia and overseas are welcome to do this course. Please click on the link above if you are interested in doing this course.

 

Current Research

I have broad research interests in conservation biology, wildlife management, animal behaviour, and physiological and behavioural ecology. Some of my current research projects and my contribution to these research fields are listed below.

 

Taste aversion learning: teaching northern quolls to avoid cane toads

 

The northern quoll Dasyurus hallucatus is an endangered marsupial predator that was once common throughout Northern Australia. The major threat to northern quolls is the highly toxic cane toad that is currently invading northern Australia. Like other native predators, northern quolls lack physiological resistance to toad toxins, and consequently, most quolls die after attacking large toads. Since cane toads invaded northern Australia, quoll populations have plummeted, and the species faces extinction on the mainland. Cane toads cannot be eradicated, and they will soon invade Western Australia.

How can we protect predators like the northern quoll from the cane toad invasion? One solution is to teach predators to avoid cane toads before they encounter invading cane toads. This could be done by using a powerful form of learning known as "conditioned taste aversion learning". Conditioned taste aversion occurs when an animal associates illness with the taste or smell of a particular food and refuses to consume that food during subsequent encounters. Taste aversion learning occurs in a wide range of animal species, including dasyurids. Recently, my colleagues and I discovered that two small marsupial predators, the common planigale and the red-cheeked dunnart, rapidly learn to avoid cane toads. These small dasyurid predators not only survive after ingesting small toads, but after eating a single toad, these voracious predators subsequently refuse to attack cane toads for up to 4 weeks.

Planigales are voracious predators that eat insects, frogs and small lizards, and they also attack cane toads.

After ingesting toads, planigales carefully sniff any toads they encounter, and reject them unharmed

There are encouraging signs of recovery of quoll populations in some parts of QLD, in areas where toads occur, suggesting that quolls can indeed learn to avoid toads. Hence, it should be feasible to train northern quolls to avoid cane toads before toads invade. This could be done on a large scale by deploying low toxicity toad tasting baits across the landscape (see Webb et al. 2008). However, before we can do this, we have to show that northern quolls (and other predators) can learn to avoid cane toads.

My honours student Stephanie O'Donnell is currently working with Sarah Hirst and Lynda Veheret from the Territory Wildlife Park to investigate whether we can teach captive reared quolls to avoid cane toads. If the work is successful, we will carry out field trials to determine whether 'toad smart' quolls have higher survival than 'toad naive' quolls. The project is in its early stages, but so far results are very encouraging. Adult male northern quolls not only survive after eating small toads, but they also show strong aversions to live toads.

Recent publications

Webb JK, Brown GP, Child T, Greenless MJ, Phillips BL, Shine R. 2008. A native dasyurid predator (common planigale, Planigale maculata) rapidly learns to avoid toxic cane toads. Austral Ecology 33:839-847.

 

Impacts of cane toads on freshwater crocodiles

Freshwater crocodiles are the top-order predator in the upstream reaches of rivers, and they can attain total body lengths of over 3 metres (mass >90 kg).  Small crocodiles prey principally upon insects and occasionally, anurans, but as they grow larger, the proportion of fish and terrestrial vertebrates in the diet increases.  Freshwater crocodiles are endemic to tropical Australia and because they have not coevolved with toads, they can die after ingesting cane toads.

The Victoria River has recently been invaded by cane toads.

A freshwater crocodile waits in ambush for passing prey.

 

 

Dr Mike Letnic (University of Sydney) and I are quantifying the impacts of the highly toxic cane toad on freshwater crocodiles (Crocodylus johnstoni) in the Victoria River, Northern Territory. During annual spotlighting surveys, we documented massive mortality of freshwater crocodiles at the toad invasion front.  Dead crocodiles spanned a wide size range (0.6 to 2.1 m long) but intermediate-sized animals (0.6–1.5 m long) were more likely to be found dead.  Population densities of crocodiles plummeted by as much as 77% following toad invasion, and population size structures changed.  The negative impacts of toads on crocodiles appear to be greater in these hot semi-arid landscapes than in cooler, higher rainfall areas where crocodiles have access to a wider prey base, and the toads are less prone to desiccation and can rehydrate in small, scattered water bodies rather than in the main river.  Hence, the impact of cane toad invasion on this top predator may increase with increasing aridity. 

Mike Letnic and Oliver Brown survey the river for obstacles prior to night time surveys.

A hatchling crocodile stalking a cane toad.

Mike Letnic cutting open a dead crocodile that has eaten a cane toad and died.

Recent publications

Letnic M, Webb JK, Shine R.  2008.  Invasive cane toads (Bufo marinus) cause mass mortality of freshwater crocodiles (Crocodylus johnstoni) in tropical Australia. Biological Conservation 141:1773-1782.

 

 

Predicting the impact of cane toads on the fauna of northwestern Australia

Cane toads (Bufo marinus) are poised to invade Western Australia, where they will decimate populations of large predatory snakes, lizards, quolls and crocodiles. What can we do about this impending disaster? My colleagues from the Western Australian Department of Environment and Conservation (Dr David Pearson, Errol Kruger, Lauren Brown), the Australian Reptile Park (John Wiegel), and the University of Sydney (Professor Rick Shine, Michelle Gray) are carrying out laboratory trials to determine whether we can teach predators to learn to avoid cane toads before the toads arrive, and to identify 'high risk' species that are likely to be seriously affected by the cane toad invasion. We are also carrying out biodiversity surveys throughout the Kimberley region so that we can detect changes in the abundance of predators after the cane toads invade W.A. Recently we discoverred that most native rodents are highly resistant to cane toad toxins. For example, the mosaic tailed rat, Melomys burtoni, kills toads with a bite to the head, flips them over, and then eats their soft internal organs, leaving the skin and parotoid glands untouched.

A mosaic tailed rat flipping over a cane toad it has killed.

 

 

Effects of wildfire on survival of sympatric snakes

Since 1992 I have been studying the ecology of two species of nocturnal snake, the common small-eyed snake Cryptophis nigresens and the endangered broad-headed snake Hoplocephalus bungaroides. This long-term mark-recapture study has revealed fascinating insights into the natural history of these snakes, and has provided data on growth rates, age of maturation, diets, and reproduction. Most interestingly, wildfires affect the survival of these snakes in different ways: a wildfire that swept through the study sites in 2001 had no effect on survival of the arboreal broad-headed snake that shelters inside tree hollows in summer, but greatly reduced survival of the terrestrial small-eyed snake.

Broad-headed snake

Study sites in south eastern Australia

Small-eyed snake

Recent publications

Webb JK, Shine R. 2008. Differential effects of an intense wildfire on survival of two species of sympatric snakes. Journal of Wildlife Management 72:1394-1398.

All photos on this website are my own and are protected by copyright. If you would like copies of high resolution images please email me.