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Nature conservation > Wildlife > Caring for wildlife > Carer's Kit > Reptiles

The outer layer of scales is periodically moulted (shed/sloughed) to allow the reptile to grow. Once this occurs, a new layer of scales grows underneath. Just prior to moulting, the outer layer of scales become loose and the body colours dull. In snakes, a scale over their eye will become opaque as it loosens from the cornea. In some lizards, bony plates called osteoderms develop beneath the epidermis for additional protection. In tortoises and turtles, the scales have fused with the ribs and vertebrae to form a shell. The upper shell is called the carapace and the lower is called the plastron.

Python head

		The skin of reptiles generally lacks glands, apart from a few specialised scent glands. This means that the skin of reptiles is dry.
Scale Terminology	Scale Count

Many lizards (particularly those of the skink family) and some snakes are capable of breaking off their tail to escape a predator (this is called caudal autotomy). This is possible because the reptiles have a cartilaginous strip that runs through each bone of the tail. The tail can regenerate; however, it regenerates as a cartilage rod, not a bone. The new tail is not as long or strong as the original.

Pink tongue lizard part of tail missing

Turtle skeleton

Feeding mechanism

The majority of reptiles are carnivorous. Among the exceptions to this rule are the green turtle, which eats sea grasses, and some large Australian skinks, which eat soft fruit.

Turtles

Turtles do not have a muscular oesophagus like most animals. They need water pressure to push food down into their stomachs. This is important to remember when you are caring for turtles.

Venom Glands and Fangs

Venom glands are modified salivary glands. Each venom gland has a single duct running forward to the base of the fangs. The venom runs down grooves in the fangs and in some species, the edges of the grooves may fuse to form an enclosed tube.

Not all snakes have fangs. Aglyphs such as pythons, have no fangs and usually no venom glands, although some secrete saliva with toxic properties.

Opistoglyphs such as the brown tree snake deliver venom through their back teeth, which are slightly larger than the rest.

Most venomous snakes found in Australia belong to the Proteroglyph group. They have one or more fangs at the front of the mouth.

Snake venom consists of a variety of enzymes and other proteins. You can often determine the type of snake that has bitten a person by examining the symptoms. Some of these enzyme types are as follows:

Neurotoxin

This is the venom of the taipan, brown, tiger snake and death adder. This causes muscle paralysis. The initial signs are usually droopy eyelids, impaired vision, diarrhoea, nausea, sweating, difficulty swallowing and respiratory problems.

Coagulant

All Australian snakes (except the copperhead) have strong coagulant properties in their venom. This enzyme causes the blood to clot, particularly in the major veins. Once the clotting effect wears off, the blood becomes anticoagulant.

Haemolytic enzyme

This enzyme causes the breakdown of red blood cells. Clinical symptoms are red or black urine.

Haemotoxic enzyme

These enzymes cause severe damage to the lining of blood vessels, which leads to small haemorrhages. The black snakes have potent haemotoxic enzymes.

Cytotoxic enzymes

The black snakes all have these enzymes in their venom. Cytotoxic enzymes destroy tissue and blood cells, which can cause a localized reaction including swelling.

Mytotoxic enzymes

This enzyme causes widespread muscle damage. It can be found in the venom of the mulga, copperhead, small-eyed and sea snakes.

Respiratory and circulatory system

Most reptiles breathe with their lungs. Some turtles breathe through the mucous membranes of their mouth and cloaca, or their skin. Reptiles with long thin bodies such as snakes and some lizards are missing or have a reduced left lung.

Reptiles must be able to move their ribs to breathe, as they do not have a diaphragm like mammals. This increases a reptile’s chance of a serious respiratory disease because it cannot cough up infectious material. Therefore, it is important to begin aggressive treatment at the first signs of respiratory distress among captive reptiles.

Reptile hearts are divided into four chambers by internal walls known as septums. However, all reptiles except crocodiles have an incomplete septum between the two ventricles (the bottom heart chambers), making it possible for oxygenated blood from the lungs to mix with used (deoxygenated) blood from the body. This type of heart cannot sustain the high metabolic demand associated with prolonged rapid movement.

Urinary system

Reptiles have a primitive kidney compared to birds and mammals. They are unable to concentrate urine properly. Depending upon the aridity of their environment, reptiles excrete nitrogenous waste as ammonia, urea or uric acid.

Olive python drinking

Thermoregulation
Heat lamp	Reptiles are traditionally termed "cold blooded", meaning their body temperature changes according to their environment. In fact, it is more accurate to call them ectothermic. With negligible internal means of maintaining a constant body temperature and metabolism, a reptile's metabolic rate adjusts to the environmental temperature. To maintain a metabolic rate necessary for day-to-day activity, a reptile will use behavioural methods to control its body temperature. For instance, they will alternate between sunning themselves and resting in the shade to keep their body temperature constant.	Blue tongue iwth heat burns

Reproduction

It is hard to distinguish between genders in many reptiles. You can differentiate between many lizards by size and colour. Male tortoises and turtles have a concave plastron and longer tails. Similarly, male snakes and lizards also have longer tails that enclose the hemipenes.

Males

The testicles of male reptiles are in the abdominal cavity, near the kidneys. In most reptiles, the gonads become enlarged during the breeding season.

Male crocodiles and turtles have a penis that functions in a similar way to mammal penises. Snakes and lizards have a pair of hemipenis, which is located in the base of the tail. During mating, each hemipene is turned inside out by contracting muscles and filling it with blood sinuses. Only one hemipene is inserted into the female’s cloaca at copulation.

Females

Brown snake eggs

In females, paired oviducts lead from the ovaries to the cloaca. These add albumen (egg white, which is absent in snakes and lizards) and the eggshell, which shows varying degrees of calcification. In general, most reptile eggs will be softer and more rubbery than bird eggs.

Python eggs

Some female reptiles (mainly lizards) can reproduce without copulation with a male (a process called parthenogenesis). This produces young that are a clone of their parents. Sperm can survive in the female tract for months or years, depending on the species. Some snakes and lizards (e.g. bluetongues and tiger snakes) incubate their eggs in their body and give birth to live young. This gives the young more protection from predators.

Nervous System and Sense Organs

Reptiles generally have small brains. For example, a 1.5m crocodile would have a 5cm long brain.

The reptilian ear has hearing and balance functions. Even though snakes do not have an external ear opening, they can still detect airborne sounds and ground vibrations

Carpet showing labial pits

Most reptiles have well developed eyes that recognise colour. Many lizards, particularly goannas, have an eye-like structure in the middle of the head, which is covered by scales. It’s unlikely that it detects images, but can distinguish light from dark and thus may be important in controlling behaviour rhythms. It occurs in crocodiles, snakes and geckos. Reptiles generally have a good sense of smell. In addition to the unusual nerves associated with smell, some reptiles have a well-developed Jacobson’s organ. In snakes and lizards with long forked tongues, scent particles are picked up on the tongue and carried to the Jacobson’s organs where they are detected by sensory cells.

Nocturnal pythons and some other snakes have heat-sensitive pits on the margins of the jaw. These are very sensitive to infrared wavelengths and can detect temperature differences of less than 0.2deg. This helps them track live mammals, especially at night when there is a considerable temperature difference between the mammal and the environment.