Blue-tongue skinks are opportunistic omnivores: their diet includes insects, larvae, snails, slugs and other invertebrates; soft fruit, flowers, greens and seeds; other reptiles, including smaller skinks; occasional small mammals, eggs and hatchling birds; and carrion.
Studies have shown they are also occasionally coprophagous — samples of herbivore and carnivore dung were taken from the stomachs of wild blue-tongue skinks.
In order to obtain all these delicacies, they forage. What they eat on any particular day depends on the season, what is available in their locale, and what they can find or chase down.
The endangered T. adelaidensis, the pygmy blue-tongue skink, is an exception to the varied diet approach as it appears to focus almost exclusively on hunting insects and spiders. (It also looks more like an Egernia or even the good old North American alligator lizard than other blue-tongues.)
Dr. Glenn Shea, an Australian herpetologist, did a detailed study of the stomach contents of two species of Tiliqua — T. multifasciata and T. occipitalis.
These are blue-tongues that live in very arid areas, with T. multifasciata favoring sandy regions dominated by spinifex grasslands. Based on distinct skull shapes and some differences in dentition, Shea suspected this might indicate the two species had evolved for eating different diets. He examined stomach contents from a large sample of both species and compared them:
“Among arthropod prey material, beetles (Coleoptera), grasshoppers and crickets (Orthoptera) and insect larvae of various types predominated in both species. Most of the insect larvae appeared to be lepidopteran, and several were large caterpillars with irritant hairs.”
When plants were consumed, the material was mostly seeds and fruits rather than vegetative material. Often large numbers of seeds or fruits were consumed, and one T. occipitalis, for example, had eaten 226 small berries.
Shea writes, “In contrast to the high frequency of insect prey, arachnid and myriapod prey were few. Similarly, molluscs were only found in Tiliqua occipitalis, and in low numbers.” (Notably, the low number of molluscs in the diet is probably due to their scarcity in these arid environments.)
Shea notes that other observers had reported T. multifasciata regurgitating seeds and ants. Stammer (1976) reported that they had been observed eating cattle dung, and Baker (1992) observed the species feeding on parakeelya, a type of flowering herb found in the Australian desert. Using specimens from the Kimberley area, Jones (1992) reported finding plant remains, arthropods, vertebrate material (carrion?), and bird eggs in the stomachs of 23 T. multifasciata.
Earlier studies of T. occipitalis found large amounts arthropods, especially beetles, plant remains, seeds and flowers of heaths (Astroloma & Brachyloma), fungi, vertebrate remains, and molluscs. One specimen had old rabbit bones in its stomach!
Shea’s research corroborated these early studies as he found very similar dietary patterns in T. occipitalis. Rather than finding major differences in diet between T. multifasciata and T. occipitalis, his study showed they both subsisted on a similar range of foods.
Shea concludes: “Both species appear to be omnivorous, with little indication of any stenophagy [diet specialization]. Both have a diet dominated by food items that are either diurnally active or able to be easily located and consumed by day, while prey that are largely nocturnally active and inaccessible by day are rarely eaten.”
Many observers have concluded that T. occipitalis is diurnally active while T. multifasciata shows a seasonal pattern: they are diurnal in spring and autumn and more crepuscular or even nocturnal in summer heat. Shea adds, “Both species appear to eat large numbers of slowly moving or non-motile food, and hence can be considered active foragers rather than ambush predators.”
Based on earlier studies and observations, it appears that T. scincoides and T. nigrolutea eat similar diets to their desert cousins, with the consideration that in their wetter climate zones, they have additional access to fruits, flowers, snails, and other molluscs. T. nigrolutea has been recorded to eat wild fungi (mushrooms). Blotched blue-tongues also ingest small vertebrates, carrion, and mammalian carnivore feces (Green & McGarvie 1971).
The amazing shingleback skinks, Tiliqua rugosa, are the best studied of the Tiliqua. A large number of studies over an extensive geographical range have shown that they eat primarily plant material with a small component of animal foods such as insects, larvae, molluscs, small vertebrates, carrion, and dung. T. rugosa populations consume roughly 80% vegetable material, including flowers, sprouts, leaves, seeds and fruit.
Here is a video of a stunningly beautiful group of western shinglebacks, T. r. rugosa with intense orange coloration. I have seen a few wild shinglebacks in Western Australia almost this vivid, but these are amazing. Not much information offered other than it’s a breeding colony.