BLUE TONGUE LIZARDS
By Frances Stopford
Genus: Trachydosaurus and Tiliqua
Shingle Back Lizards – Trachydosaurus rugosus
Shingle backs have a diet that may include insects, baby birds, carrion and vegetation. “They eat all sorts of things, but basically most live food is too fast for them so 95 percent of their diet is flowers and berries and things like that” Mike explains. Spring is when the lizards are most active, feeding and breeding while conditions are favourable. “They have a short period to stock up on food that has to last them the whole year”. At the season's peak Mike may catch 40 or 50 lizards in a day.
Adult shingle backs weigh around 600 – 700g, with females usually a little heavier than males. Babies weigh about 100g. Taking three years or so to reach full size. Around the Mount Mary area Mike found that only about 16 percent reach their first birthday but annual adult survival is about 80 – 90 percent.
The data Mike and his students and assistants have gathered from more than 20,000 captures of over 5,000 lizards have allowed him to build up an extremely detailed picture of the lives and loves of these lizards. Probably the most startling discovery made as a result of these studies conducted during the 1980's has been that the lizards are monogamous, returning year after year to mate with the same partner. At winter's end shingle backs are usually found alone, but as spring progresses pairs start to form (see chart on next page) and may be found curled up together in retreats, basking side by side or feeding together. For days at a time the male follows the female around, usually separated by only a few centimetres, one pair being found together for ten consecutive years.
Recent investigations on the faithfulness of the lizards shows that all is not quite what it seems. When a male has mated with a partner he'll wander about to see if there are any other females around. Using DNA * fingerprint techniques, it has been found that some of these wanderings males are successful, females occasionally producing young that weren't fathered by their usual partner. “It was a surprise to get these results”, Mike said.
Radio tracking gave an insight into other discoveries, such as the fact that females can recognise their offspring, even after months apart; they use the same home range year after year; they can find their way back if shifted away.
A Shingle-Back Lizard's Year
A shingle-back's year is a short one. It has only a few months to feed and mate before summer's heat kills the vegetation it eats and makes life in the open unbearable. Shingle-backs are the only lizards known to exhibit fidelity and during the short period of activity males must find their partner of the previous year and then mate with and defend her. The rest of the year is spent sheltering, often down an abandoned rabbit burrow.
This excerpt from an entry in Dampier's journal is part of the very first description of a uniquely Australian reptile. And his account could only be describing a sleepy lizard:
“They are very slow in motion; and when a Man comes nigh them they will stand and hiss, not endeavouring to get away. And at the Rump, instead of a tail there, they had a stump of a tail which appeared like another Head. The body when opened hath a very unsavoury Smell. I did never see such ugly Creatures any where but here … but tho' I have eaten Snakes, Crocodiles and Alligators, and many Creatures that look frightfully enough … yet I think my Stomach would scarce have serv'd to venture upon these … both the Look and Smell of them being so offensive.” William Dampier 6 August 1699 Shark Bay, WA.
Obviously Dampier was not impressed by the lizards.
Pygmy Blue Tongues – Tiliqua adelaidensis
They were first discovered in 1863, but until recently had only been seen twice this century – the last in 1959 – and was represented in museums by only 20 specimens. Pygmy bluetongues are only a mere 16cm in total length and their tongues are actually pink. They are not as robust or as strickling coloured as a normal blue tongue although they are related to blue tongues defined by scale pattern and bone structure.
This lizard was thought to be extinct for many years until rediscovered in 1992 by two biologists, Graham Armstrong and Julian Reid. Upon finding a dead brown snake killed on the road and checking the stomach content for food consumed they came upon a pygmy blue tongue. Dr Mark Hutchinson of the South Australian Museum in Adelaide led a concerted effort to find a viable population. Over the next three years, though searching revealed only dead blue tongues, two killed by birds of prey and the third was yet again found inside another brown snake. Tim Milne, a PhD student from Flinders University , found the first live lizard. Along with Mark and two other assistants they sank buckets in the ground, each placed under a fence that would direct lizards into it. Twenty lizards were caught over a five-week period, with 14 males, and six juveniles, no adult females were caught.
After attaching radio transmitters they discovered the pygmy bluetongue lived in holes in the ground preferring trap door spider holes found in paddocks with their only shelter the hole itself and the crops grown above. There are some female lizards that don't appear to ever have swapped holes. They have been caught eight or ten times over the past three years and they're always in the same hole. They spend most of their time sitting and basking, grabbing insects as they go past. They rarely leave their burrow – less than 3 percent of their normal activity period. If caught out of their hole they freeze which along with their sedentary lifestyle and dried grass colour, goes a long way towards explaining why they remained unseen for such a long time. None of the local farmers, many whom have large populations on their land, had seen one before they were alerted to their presence.
None of the areas where the pygmy blue tongues are found are protected and Tim has been getting the local community involved in conservation of the pygmy and working with the students from Burra Secondary School South Australia . On land owned by the school he has been looking at how sheep grazing affects the lizards, comparing their numbers in grazed and ungrazed paddocks. The students help by examining burrows for occupants. The long-term chances of survival are good with the estimated population at around 5,000 lizards. Tim has found no evidence of any recent dramatic decline and has actually been able to increase numbers artificially by creating new burrows.
The Six Australian Blue Tongues
Blue Tongue Lizards In Suburbia
Eastern blue tongues live happily in suburbia – up to a point. If encountered they will puff their bodies up, hiss angrily, show their tongue and they may even charge at you – this tends to put off most predators including a lot of humans. If picked up and held properly though they will sit quietly on your hand apparently indifferent to their situation. This pleasant disposition, together with their suburban abundance, has made them a popular part of growing up in eastern Australia . They hang around compost heaps and under garden refuse, eating snails and other pests. Although a boon to gardeners, this cohabitation isn't always as successful as it might be, for we humans bring to the relationship numerous dangers for our reptilian offsiders.
Snail bait – bluetongues happily eat any dead corpses laying around and thus get poisoned themselves. Poisonous plants and poisoning plants can cause problems as the blue tongue likes to eat some plant life.
People will often ring WIRES or other rescue organisations to come and take the lizard away. It then will be relocated as close as possible to the area it came from. In bushland or a suitable backyard where it can roam free. Injuries, if any, are assessed, treated and the blue tongue held for rehabilitation and/or released as soon as possible.
Despite these and plenty of other hazards, blue tongues continue to live unobtrusively among us, much to the quiet delight of many Australians. Lizards aren't everyone's favourite animals but it seems that blue tongues have quietly crept to near icon * status in this country and anyone who gets to know a blue tongue an any kind will eventually be seduced by its serene charm.
Reference: Australian Geographic July – September 1999. By Geordie Torr Edited by Frances Stopford
Blue tongue lizards – skinks are distributed over much of Australia as seen by the maps on the previous page (The Hawkesbury Herpetologist No. 30 November 2003). Some are similar in appearance and it is mostly colour that distinguishes them from each other although the Shingle-back is vastly different with a pine-cone appearance and the pygmy blue tongue is very small. All six blue tongues produce live young the number varying from 1 – 4 for Shingle-backs to as many as 25 for the common bluetongue. The blue tongue will thrive in captivity, as long as a few simple rules are followed, with little trouble to the keeper. They have relatively short, pentadactyle * limbs and short tails, anterior ear lobules usually present, smooth scales and movable lower eyelid. They are active during the day feeding on both animals and plants. They often reach adult size by the time they are two years old and have been known to live up to 30 years in captivity.