Eastern bluetongue skink

The field of ecology is brimming with extraordinary and unexpected stories. And they don’t come any more intriguing than one involving the much loved bluetongue skink (Tiliqua scincoides), a common resident in urban parks and gardens.

Research undertaken by the University of Sydney discovered an unexpected connection between the bluetongue and 2 other completely unrelated species widespread in south east Queensland, the weed mother-of-millions (Bryophyllum spp), and the introduced cane toad (Rhinella marina). Mother-of-millions is originally from Madagascar and the cane toad from South America, yet despite their geographic and phylogenetic distance, both species produce almost identical toxins. The Sydney researchers discovered that the omnivorous bluetongue skinks, consumers of both cane toads and mother-of-millions, showed a higher physiological tolerance of toad toxins in areas where they had been exposed to the toxic mother-of-millions prior to their exposure to cane toads.

The benefit conferred by pre-exposure to mother-of-millions may be important. In the Darwin region, where mother-of-millions is absent, field surveys undertaken between 2005-2009 recorded a sharp decline in bluetongues following the arrival of cane toads in the survey area.

A common resident of many suburban gardens in southeast Queensland the bluetongue skink will often forage on an open compost heap. While it feeds naturally on a variety of insects, molluscs, plants and native fruits, it will also happily eat other fruits such as mangoes, grapes and bananas.

Bluetongues will happily live in suburbia if they can find suitable habitat. Some bluetongues have been known to live for years in the same garden if there is enough food and shelter and no dogs or cats to harass them. As slugs, snails and insects are also favoured foods, it is important not to use garden pesticides or snail baits if you want to attract and protect bluetongues in your garden.

Bluetongues give birth to live young 3 to 5 months after mating. Usually around 10 young, but as many as 25, will fend for themselves within a couple of days of their birth.

Predators include kookaburras, some small raptors, large snakes and introduced dogs, cats and foxes. In urban areas one of the leading causes of death is from dog attack. Data collected by the New South Wales Wildlife Information and Rescue Service (WIRES) showed that causes of death varied seasonally, but overall the highest identifiable cause of death was dog attack, followed fairly closely by cat attack. Interestingly, 75% of dog attacks involved adult bluetongues while around 75% of cat attacks were on juveniles. In the Sunshine Coast region, dog attack is also a common cause of death and injury to bluetongue skinks. Of 840 bluetongue skinks admitted to the Australia Zoo Wildlife Hospital between 2005 and 2017 from the Sunshine Coast local government area alone, 44% resulted from dog attacks.

Article and images by Julie O’Connor, senior conservation partnerships officer, Sunshine Coast Council

References:

• Australian Museum
• Australia Zoo Wildlife Hospital admissions data 2005 -17
• Capon, R. J., Hayes, R. A, Hagman, M., and Shine, R. 2008. Cane toad chemical ecology: controlling an invasive pest. Planta Medica 74:1134
• Cogger, H. G. 2014, Reptiles & Amphibians of Australia, 7th Ed, CSIRO Publishing, Australia
• Koenig, J., Shine, R., and Shea, G. 2002. The dangers of life in the city: patterns of activity, injury and mortality in suburban lizards (Tiliqua scincoides). Journal of Herpetology, 3 1: 62-68
• Price-Rees, S. J., Brown, G. P. and Shine, R. 2012. Interacting impacts of invasive plants and invasive toads on native lizards. The American Naturalist, 179: 3. 413-422.