Aggression in Lizards

Aggression in Lizards - Symptoms, Causes, Diagnosis, Treatment, Recovery, Management, Cost
Aggression in Lizards - Symptoms, Causes, Diagnosis, Treatment, Recovery, Management, Cost

What is Aggression?

Many forms of aggression occur when there are too many lizards in a cage or enclosure. Attacks on cage mates are common and can result in severe injuries. Most lizards are solitary animals, and though some breeds have been known to live happily together to conserve moisture or during winter hibernation, many lizards will become aggressive once they reach adulthood. Aggression directed at humans can also be territorial, or it can be the result of forceful handling, a forced displacement from its territory, or the removal of its resources, often food. To a lizard, mishandling can be interpreted as predation, and the aggressive behavior is an innate response.

Aggressive behavior in lizards is a common and natural occurrence that is seen in both wild and captive animals. Actions that are often misinterpreted by owners as an attack or dislike towards them by their lizards are often behaviors that are innate in all reptiles. Lizards will show aggressive behaviors when they feel threatened, or are protecting food, territory, or their mate, all of which are responses that ensure their survival in their natural habitat. However, when behavior becomes too aggressive, there are measures you can take to ensure the safety of your lizards, and the humans in their environment.

Symptoms of Aggression in Lizards

Symptoms of aggression in lizards are seen by their behaviors. These can often be categorized as challenge displays, which are responses to another male presence and can lead to fighting, or assertion displays, which occur without another male present. Behaviors include: 

  • Push-ups 
  • Head bobbing
  • Head shaking
  • Tail raising
  • Tail whipping
  • Body flattening
  • Arched back
  • Aggressive chasing
  • Biting
  • Open mouth gaping
  • Extends dewlap
  • Lateral posturing
  • Extends dorsal and/or nuchal crests
  • Extends both crests 
  • Flattens sides 
  • Body raising or shaking
  • Throat enlargement
  • Striking with head or tail
  • Puffing up
  • Turning sideways
  • Tongue licking
  • Hissing
  • Extending front two or all four limbs
  • Tail fractures due to tail whipping


Evidence that cage mates are getting injured from aggressive behaviors include:

  • Head injuries
  • Extremity injuries
  • Bite wounds
  • Often seeking raised temperatures to reduce stress

Types of Aggression in Lizards

Aggression in lizards can be defensive, offensive, or acquired.

Defensive aggression

These behaviors occur due to a perceived threat, such as fear of a predator or defending a territory; sudden movements can cause a shy or prey lizard to be on its guard, and exhibit behaviors such as hissing, biting, defecating, crypsis, or locomotor escape.

Offensive aggression

These behaviors are more common with more aggressive or venomous hunter species, such as Tegus and monitors, and are related to breeding and territory; offensive behaviors are more aggressive behaviors, and lizards are often quicker to strike and defend themselves than prey lizards (you will more likely see these lizards come after the threat and attack, rather than attempt an escape).

Acquired aggression

This type of aggression is seen upon sexual maturity, and during the breeding season.



Causes of Aggression in Lizards

There are many reasons why a lizard may exhibit aggressive behaviors toward owners or other lizards. They include:

  • Defending territory
  • Need to establish social dominance
  • Defense of resources, such as food, mates, nesting sites, basking sites, or predator refuges
  • Fighting over breeding rights
  • Introduction of new male lizard into environment
  • Overcrowding
  • Lack of adequate food resources
  • Changes in hormone levels, often during breeding season
  • Stress due to captivity
  • Defending from a perceived predator
  • Forceful handling by humans
  • Lack of escape choices in environment
  • Higher than normal incubation temperatures before hatching
  • Pain


Diagnosis of Aggression in Lizards

The diagnosis of aggression in lizards is mostly based on the behaviors seen in your lizard. Monitor your lizard and report any aggressive actions to your veterinarian. Your vet may need to know about your lizard’s environment, if it is solitary or has cage mates, and what kinds of things are in its environment, such as food resources, basking sites, and hiding places. Your vet may also want to witness how you handle your lizard to see if it is perceiving you as a threat.

A physical exam and an X-ray can also detect any injuries that are causing pain, or if there are injuries due to the aggression, such as a tail fracture. Also, report any injuries sustained by your lizard’s cage mates. Your veterinarian will take all these factors into account, as well as the age and species of your lizard to come up with a diagnosis, as well as a cause for the aggression.



Treatment of Aggression in Lizards

Aggression in lizards can be treated with a series of environmental changes and interaction modification. These may include such actions as:

  • Provide an appropriately sized enclosure
  • Provide multiple feeding stations, water stations, hiding places and basking sites
  • House lizards separately that cannot cohabitate
  • Provide visual barriers between individual cages to reduce perceived threats
  • Species that can become aggressive toward their own reflection, such as chameleons, need non-reflective materials as cage walls rather than glass
  • Gradually introducing new lizards in species that can cohabitate
  • Species that can cohabitate need to be monitored, and aggressive individuals removed as needed
  • Reduce the amount of daylight hours
  • Give your lizard a surrogate mate, such as a stuffed lizard
  • Reduce the amount of animals in a breeding group
  • Monitor breeding groups for aggressive behaviors
  • Separate animals for feeding during breeding season
  • Use gentle handling and slow, easy movements when handling your lizard
  • Keep handling sessions short until your lizard gets used to you
  • Seek counterconditioning strategies from an expert to reduce aggression towards you if other solutions are not working

For injuries sustained due to aggression, wounds are often treated with topical antibiotics and dressings if needed. Tail fractures can result in tail necrosis or gangrene, and are usually treated with an amputation, performed by bending the tail until it breaks off at a natural fracture plane, then leaving the tissue unsutured to encourage regeneration. Often, the tail grows back, although it can be altered in appearance or length.



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Recovery of Aggression in Lizards

Aggression in lizards is a natural occurrence, and should not be punished. Rather, using strategies to create a less threatening environment can reduce or eliminate aggressive behaviors, and allow your lizard to be stress-free, and you injury-free. If your lizard required a wound dressing or an amputation, be sure to give it cage rest, change dressings as needed, and administer any medications from your veterinarian as directed.



Aggression Questions and Advice from Veterinary Professionals

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