There are three species of snakes and seventeen species of lizard found in Tasmania. Of these, seven lizards have distributions restricted to Tasmania.
Tasmania's relatively cool climate and high mountain ranges provide certain challenges for reptiles. Reptiles need to raise their body temperature, usually by basking or by absorbing warmth from rocks which have been heated by the sun. Most species only become active when the air temperature is well above 15 degrees Celcius. Consequently, some species of reptile enter a torpor over winter and most have developed strategies and adaptations to thrive in Tasmania's cooler environment.
Reptiles are an ancient group of vertebrate animals that first appear in the fossil record some 250 million years ago. Since then they have evolved into many different groups, many of which are extinct, others which are no longer called reptiles, such as birds and mammals. There are still five major orders of reptiles in the world today. These include:
- The Order Crocodilia including crocodiles, alligators, caimains, and the like. The Indopacific Crocodile of northern Australia is the largest living reptile in the world today.
- The Order Testudines include the turtles, terrapins and tortoises. There are no native Testudines in Tasmania, but we are sometimes visited by marine turtles such as the Luth or Leatherback turtle. The Long-necked terrapin is also present in the state, but is thought to have been introduced.
- The order Rhynchocephalia is restricted to the Tuataras of New Zealand, which look superficially like lizards.
- The order Squamata is the most diverse and widespread of the groups, containing snakes in the suborder Serpentes and lizards in the suborder Sauria.
There are advantages to being a reptile. Reptiles are ectotherms ( which translated means "outside heat"), using external sources of heat to raise their body temperature sufficiently to become active. By contrast mammals and birds are endotherms ("inside heat") using internal processes to maintain their body temperature. Producing your own body heat is expensive. Mammals use between 70-90% of the food they eat just to maintain their body temperature, so of course they have to eat a lot. Reptiles can go for days, even months without food, and the food that they do eat is used in making more reptile. Most reptiles are able to raise their body temperature rapidly above that of the air temperature on sunny days. They achieve this by choosing basking sites which are sheltered from the wind and exposed not only to direct sunlight but to the warmth reflected off rocks or logs. If the substrate has been warmed by the sun they will often flatten themselves against it to absorb as much heat as they can.
All species of reptile found only in Tasmania give birth to live young rather than laying eggs. In some cases the eggs merely develop within the body until they are ready to hatch. The eggshell has been dispensed with, but the young are still born within an amniotic membrane. Other species, such as the Grass skinks, have a well-developed placenta and the health of the newborn young is more closely tied to the health of the parent female. In Tasmania's relatively cold conditions keeping the young within the body allows the parent to have greater control over the incubation temperature and the chances of survival are increased. All over the world there is a trend towards live-bearing amongst reptiles in colder areas.
Reptiles are well adapted to survive dry conditions. They do not lose moisture through their skins by sweating and land-dwelling reptiles conserve water by excreting their uric acid in a solid white pellet at the end of their droppings. In other words, these reptiles don't pee. Many reptiles have other adaptations for life in a dry environment. For example, all snakes and many lizards have a transparent scale permanently fixed over the eye. As well as providing protection for the eye, the transparent scale prevents moisture loss through evaporation. Most small Tasmanian skinks have a transparent scale in their lower eyelid which performs a similar function. These lizard normally close their eyes when at rest, but can still see. If there is any movement that might mean danger or food, they quickly open their eyes.
Undoubtably the biggest threat to reptile fauna in Australia is destruction of habitat. The preservation of adequate habitat is vital to effectively conserve the diversity of Tasmanias flora and fauna. All bush, whether it is a council reserve, a back block, or a patch of scrub on a farm that hasn't been cleared, is home to wildlife. Off reserve conservation is important (in some cases essential) for the long-term survival of many species of animals and plants. If you have any bush on your property, keep it weed free. Many reptiles rely on rocks and logs for shelter. You can help protect reptiles by buying quarried stone for rockeries rather than collecting bushrock. When collecting firewood, leave some larger logs (and all hollow logs) behind. Hollow logs provide shelter not only from cold, rain and predators, but shelter animals from fire as well. It is important to remember that while hollow logs do, in fact, grow on trees, they usually take at least 80 years to develop. A long time frame is needed when managing vegetation.
Cats cause a great deal of damage to Australia's fauna. Unfortunately, there is little difference between feral and domestic cats in this regard, except that feral cats are hunting to survive. If you own a cat, the responsible thing to do is to have it desexed and keep it indoors at night. Putting a bell on a cat (unless it's a cow bell) will not stop your cat from hunting wildlife. Cats tend to pounce on prey rather than rush at it so by the time an animal hears a bell it's often too late. By using two bells you can lessen, but not eliminate, the impact that your cat might have. Never dump cats or kittens in the bush. Take them to an animal shelter or have them humanely put down.
Other introduced animals that feed on reptiles may have a serious long-term impact on populations. Laughing Kookaburras and Lyrebirds have both been introduced to Tasmania. Both species feed on lizards. Foxes are known to feed on a wide range of animals and potentially pose the greatest threat to Tasmania's status as a last refuge to many native animals.
The movement of reptiles into the state has the potential to introduce disease and competition into Tasmanian environments. The importation of reptiles into Tasmania is illegal with out a scientific permit. See the Department of Primary Industries and Water for details on keeping reptiles for information on the responsibilities that keepers have.