Understanding Reptile Behavior

Reptiles often exhibit defensive aggressive behaviors, including inflation of the body, broadside posturing, dewlap extension and open-mouth threat (Figure 3-2). Some can even spray a noxious substance.


Many pet owners are apprehensive about handling reptiles because of the myth that they bite. While this may be occasionally true, it is not usually the case.

Body language

While every animal is different there are some bare basics that most animals will display in body language. These can be as subtle as a little flick of the tongue to more noticeable movements like their head, body or tail. If your snake is displaying any of these it can help you understand their mood, what they need or want and even whether they are stressed.

For example, if you are handling your snake and they begin to show signs of being agitated it could be because they feel threatened or possibly hungry and want food. They might start flicking their tongue a lot more frequently or short little flicks to check out the environment around them. They might be moving around a little more erratically and following any movement with their eyes or if they are really agitated they might follow the movement with their whole body.

They may also stop using sidewinding and serpentine motions and move more rectilinear or concertina style instead. They might stop orienting to stimuli in a fluid manner and instead become more erratic in their orienting and try to run away from things they don’t recognize. Heavy breathing will occur and they might not be consuming as much water as usual. These are all indicators that they are feeling stressed. If you keep up with their antecedents and reinforcment history and do things to prevent them from being over-stimulated you can hopefully avoid aggression or bites.


As in other vertebrates, reptiles display a range of behavioral characteristics. Some are shy and timid while others are gregarious or even aggressive. These characteristics may be influenced by age and environmental conditions. For example, a recently published report indicated that the amount of humidity in the environment is crucial to the growth and morphologic development of tortoises.

It is important for the veterinary practitioner to understand these differences as they can affect a pet’s health and wellbeing. For instance, even the most tame of pet lizards can become fractious when frightened. A frightened lizard will flatten laterally, widen its eyes, and sometimes extend the dewlap in a defensive posture. This reaction is a natural defense mechanism that should not be interpreted by the owner or practitioner as signs of disease.

It is also worth noting that many of the same types of socialization behavior that occur in mammals, birds, and fish are present in reptiles. These include a tendency to become tame or fractious around certain people and the ability to recognize individuals in captivity. In addition, some lizards and snakes can be taught to respond to hand signals in much the same way that humans learn to speak by listening to their parents. However, it should be emphasized that reptiles cannot be tamed in the same manner as mammals or birds and that the use of terms such as personality, temperament, or temperament syndrome is highly controversial.


Reptiles exhibit a wide variety of behaviors and structural morphologies that are designed to help them escape notice, fend off enemies, reproduce, obtain food and adapt to their environment. Many of these behaviors and morphological adaptations could be interpreted by an uninformed pet owner or veterinary clinician as signs of disease or trauma.

Behavioral patterns in reptiles that change with ontogeny have not been studied to the same extent as in fish, birds or mammals. This is of particular importance in the veterinary clinic as inappropriate interpretation of reptile behavior could lead to unnecessary handling stress, potential injury or a misdiagnosis.

For example, a lizard that has been moved from its terrarium to an open sunny enclosure may start the day by exposing only its head from a rock crevice to pick up solar heat absorbed by its bare skin (thigmothermy). This is a normal thermoregulation strategy for this species but to the uninformed observer it might appear to be a sign of illness or injury.

Some reptiles use a “stargazing” posture when the animal is ill. This appears to be a response to parasitic, viral or bacterial infections of the central nervous system and involves raising one foreleg while balancing on the opposite hind leg. The behavior is not observed in healthy animals. Some snakes empty their musk glands, located in the cloacal area, when they are angry or frightened. This defense strategy may be dangerous for the handler as these glands contain toxins that can cause burns and abrasions.


Reptiles have evolved a wide variety of behaviors and morphological adaptations that allow them to escape from predators, reproduce and survive in their environments. Some of these are clearly visible to the veterinary clinician, but others are not and may only become obvious when a health problem arises. It is important to be able to recognize and interpret defensive behavior in order to minimize injury to the patient and to the staff.

It is also important to understand that many reptiles have physiologic responses that may be interpreted as defensive or aggressive. For example, snakes that are overhandled soon after feeding may regurgitate their food in a physiologic response. It is important to be able to differentiate this from a pathological presentation.

Many reptiles require special care, especially if they are exotic. It is essential to research the species that one is interested in before purchasing so that the proper housing, diet and environmental needs can be met. The use of enrichment in enclosures is essential to promote natural behaviors and reduce stress, which can lead to immunocompromise and disease.

It is also important to remember that reptiles can learn. Enrichment can be as simple as placing food in branches, hiding spots or underground, which encourages foraging and provides mental stimulation. It is also important to provide adequate exercise for the species and to avoid overfeeding, which can contribute to gastrointestinal disorders.