Western gorilla (Gorilla gorilla) Male western gorillas display a wide range of both vocal and gestural communications when threatened by an opponent. A silverback (alpha male) will start hooting, throwing, chest pounding, leg kicks, and sideways running when approached by another male. This is done to intimidate the opponent and show physical abilities without actually making any physical contact. Threats Threat behaviour is any behaviour that signifies hostility or intent to attack another animal. Threat behaviour is meant to cause the opponent to back down and leave. While ritual display can be used for an array of reasons or communicative purposes, threat distinctly is meant for hostility and is the last step before fighting or submission. Threat does not involve physical contact with another animal. Any threat behaviour most often elicits other agonistic behaviour in the recipient. This initiation of threat will result in a display of physical attributes, a fight, or submission; the behaviour or sequence of behaviours depends on what resources are being fought over and each individual's chance of winning against his opponent. In any animal species, threat always contains components of attack and fleeing, which expresses an animal's readiness and likelihood of winning. An intimidation display with a means to threat are exhibited through: hair bristling, feather ruffling, raising skin folds and crest, teeth displaying, horn displaying, making sound, etc. Example: Frill-necked lizard (Chlamydosaurus kingii) Chlamydosaurus kingii, an Australian agamid lizard, uses its frill as a way to display size and aggression to opponents. It is one of the largest and most notable displays seen in the animal kingdom. In comparison to its body size, the frill can flare out to make the lizards head look several times bigger, and it displays bright orange and red scales. Males of C. kingii fight and display frills often during the mating seasons. The male ritualistic display includes repeated partial erections of the frill, head bobbing, tail lashing, and waving of forelimbs. Agonistic fighting Actual fighting in contests is rare because of the risk of injury to both participants. It is most likely to occur when individuals are similarly sized, or when the contested resource is essential for reproduction or survival. Even when agonistic behaviour escalates to fighting, restraint may be used. Fish such as Oreochromis mossambicus often exhibit aggressive displays, but rarely fight to the point of injury or bodily harm. This is also the case in fights