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.
