Agonistic behaviour

Scott and Fredericson describe that agonistic behaviour is displayed in a variety of different circumstances in response to different stimuli. Scott and Fredericson studied mice and rats, and classified three main categories of agonistic behaviour these animals display, which include preliminary behaviour, attack, and defensive and escape behaviour. Preliminary behaviour describes the behaviours displayed by these rodents if fighting does not immediately begin. These may include involuntary behaviours such as hair-fluffing, where the rodent's hair stands up on end with no prominence on a particular region of the body, or tail-rattling where the rodent's tail experiences muscle contraction and twitches from side to side, making a loud sound if struck against a hard object. Another preliminary agonistic behaviour demonstrated by mice is referred to as mincing behaviour which is when mice circle their opponent before a fight begins. The fight itself is classified as one of the pattern of behaviour that occurs and involves physical violence between the rodents. Finally, the defensive and escape behaviour occurs usually immediately after the fight and is displayed by the mouse that was defeated in the fight. The defeated mouse, if allotted space, will run away and try and take shelter from the victorious mouse. If it is not possible for the mouse to physically run and escape because space is not available, the defeated mouse will rear up on its hind legs and hold its front legs up in a way that is characterized as a "submissive stance". These are examples of the physical behaviours that are responses to conflict in mice. == Evolution and ecology of agonistic behaviour: Stomatopoda (praying mantis shrimp) ==

Agonistic behaviour is a result of evolution, and this can be studied in a number of species facing different environmental pressures. Though agonistic behaviours can be directly observed and studied in a laboratory setting, it is also important to understand these behaviours in a natural setting to fully comprehend how they have evolved and therefore differ under different selective pressures. Mantis shrimp, predatory crustaceans, are an example of an aggressive and territorial organism whose agonistic behaviour has been studied in an ecological and evolutionary context. Mantis shrimp are among the world's most aggressive crustaceans. These sea creatures are secretive, but highly alert and active predators who inhabit burrows and cavities along coral reefs, rocky coasts, and muddy shores of tropical and subtropical waters. This display behaviour is an evolutionarily conserved behaviour in agonistic displays. Evolutionary differences are clear in "smasher" and "spearer" stomatopods who inhabit different substrates and either burrow or do not burrow. Caldwell et al. describe these differences with respect to a behavioural display called a "meral spread". Further studies on N. bredini, however, suggest that meral spreads are not directly related to strike force or fighting ability. An evolutionary divergence between stomatopods is described in appearance of the meral spot, which is a dorsal, medial groove on the raptorial merus of the raptorial appendage. Smasher stomatopods, which are species that tend to inhabit cavities within rocks or coral, have brightly coloured meral spots which aid in making the meral spot more visible during these meral spread displays in fights. These bright meral spots possessed by smashers are either yellow, blue, red or white and are outlined by a conspicuous black pigment. Conversely, spearing Stomatopods or some smashing species that do not inhabit rock or coral cavities, have much duller meral spots. This correlation suggests to researchers that habitat and meral spot colouration have co-evolved, and those that inhabit burrows possess these bright spots and those species that do not have dull spots. This demonstrates how ecology and evolution of organisms within the same order directly affects agonistic behaviour. == Hormonal influence ==

Agonistic behaviour is influenced by the action of hormones such as vasopressin, which is a small peptide synthesized in the brain by magnocellular neurons. Agonistic behaviour itself may be divided into two categories: offensive or defensive. Each of these classes of agonistic behaviour are the result of different neurobehavioural pathways, and offensive and defensive agonistic behaviour are elicited by different stimuli. Offensive behaviour specifically has been studied in the context of intruder interactions in studies employing rodents as test subjects. For example, when an unfamiliar male hamster is placed into cage of a conspecific male, a stereotypical suite of agonistic behaviours follow. The resident male approaches the intruder and sniffs him intently, threatens the intruder with an upright posture, and finally initiates a physical attack on the intruder. The resident male attacks the belly of the intruder male and attempts to maneuver the intruder onto his back. This antagonist has been known to decrease the tendency of offensive aggression via injections into the ventrolateral hypothalamus, therefore is able to act on multiple regions of the brain and exhibit the same effects of offsetting this agonistic behaviour. While vasopressin plays a role in offensive aggression in agonistic behaviour, serotonin also plays a role in aggressive behaviour in rodents as well as similar effects in humans. Research has shown that increased levels of serotonin or stimulating serotonin receptors in rodents corresponds with decreased agonistic behavioural display, such as behaviours like attacking and biting. Male resident hamsters, which typically always display stereotypical offensive agonistic behaviours, display a significant decrease in bite attempts toward intruder males when treated with a serotonin reuptake inhibitor called fluoxetine. Vasopressin and serotonin both play significant roles in agonistic behavioural displays, and understanding the interaction of these two opposing neurotransmitters is important in fully understanding the neurobiology of agonistic behaviour. Glucocorticoids also have reported effects on agonistic behaviour in mice, though these effects are not as thoroughly understood as effects of androgens. Research has demonstrated that in mice that have been defeated in agonistic encounters have elevated levels of corticosterone, which appears to enhance submissive behaviour and therefore has opposing effects on agonistic aggressive behaviour. ==Prediction of winning==

The type of agonistic behaviour observed, whether it be aggressive or submissive, all depend on the likelihood of winning. For instance, size is usually a good predictor of fighting success, and many animals will display to flaunt their size. Animals are better able to assess their next form of agonistic action by judging the opponent's size and if they are likely to win a fight if a physical altercation were to occur. Example: Stalk-eyed flies (Diopsidae) In aggressive behaviour by male stalk-eyed flies the males "square off" by displaying their eyes. Females show a strong preference for mating with males with longer eyestalks. Due to the female preference, males have evolved to compete with each other for mating rights. In the threat display the two flies face each other head-to-head, with their forelegs spread outward and parallel to the eyestalks. This behaviour allows each individual to judge the distance between its competitor's eyes. Eyestalk length increases with body size, and males with shorter eyestalks will usually retreat. A further distance between the eyes conveys a bigger body size, and a better chance of winning. ==Avoidance==

Physical fighting is actually rare between animals. It would seem that normally the more aggressive an animal is, the more it has to gain. However, in a normal scenario if an animal is too aggressive it might face an unacceptably high cost such as severe injury or death. Unless an animal has a sure indication that they will win without injury, or the resources are valuable enough for the risk of death, animals usually avoid fighting. An animal must weigh the relative costs and benefits of fighting. If the costs are too high, avoiding a fight is preferable. ==Ritual display==

For animals, display is any behaviour modified by evolution that is used to convey information. To avoid the heavy cost of fighting, animals have evolved sophisticated rituals, which they use to bluff their opponents into backing down or fleeing. The cost-benefit model of display makes three assumptions: (1) type of display varies depending on the cost; (2) the risk of the display increases as the effectiveness of display increases; and (3) the value of resource being disputed over determines the choice of display used. Western gorilla (Gorilla gorilla) Male western gorillas display a wide range of both vocal and gestural communications when threatened by an opponent. Oscar cichlids Oscar cichlids (Astronotus ocellatus) are able to rapidly alter their colouration, a trait which facilitates ritualised territorial and combat behaviours amongst conspecifics. Individuals of another cichlid species, the blunthead cichlid (Tropheus moorii), defend their feeding territory with a display, quivering the tail and fins to intimidate, or an attack, darting at the intruder and chasing them away. Astatotilapia burtoni cichlids have similar displays of aggressive behaviour if they are territorial, which include threat displays and chasing. ==Threats==

Threat behaviour is any behaviour that signifies hostility or intent to attack another animal. 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. Spider monkeys Spider monkeys (genus Ateles) defend their territory by screams, barks, rattling or dropping branches, and urinating and defecating on intruders below. ==Agonistic fighting==

behaviour in a zoo between two chickens 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 among some male venomous snakes; they wrestle, but refrain from biting. Examples Black mamba (Dendroaspis polylepis) Agonistic fighting for black mambas involves a wrestling match in which opponents attempt to pin each other's head repeatedly to the ground. Fights normally last a few minutes but can extend to over an hour. ==Submissive behaviour==

Submissive behaviour involves an individual indicating by an act or posture that it will not challenge a dominant individual in a social group. Social interactions among bearded dragons (Pogona vitticeps) consist of a unique set of movements or visual signals. Waving is one of the most visible signs of submission one lizard can display to another. The lizard rests on three of its legs, raises one of the front arms and then slowly waves the arm in a circular motion. This circular motion, along with the dragon puffing up slightly, shows submission. This display is seen between opponents, as well as adolescents towards adults. == See also ==