Steve Parker - Display: Appearance, posture and behaviour in the animal kingdom

The peacock, Pavo cristatus, has become symbolic of the incredible courting displays performed by so many male creatures. Dozens of animals have peacock in their name, from worms and spiders to flounder fish and monitor lizards.

COURTSHIP AND MATING

Displays take centre stage during the breeding season. Colours and patterns are joined by jumps, bows and other forms of dancing, also vocalizations ranging from simple clicks and pops to lengthy, complex bird song, the orangutans remarkable long call, and the incredibly complicated compositions of great whales. The vast majority are enacted by males, to attract females for mating. This is especially familiar in birds. Males moult or shed their relatively dowdy, non-breeding feathers for bright, colourful breeding or nuptial plumage. Meanwhile most females remain plain and camouflaged, since in many species, they alone raise the young.

In some animals, females choose males based on a particular anatomical or behavioural feature, such as a betta fishs flamboyant fins, a deers elaborate antlers, or a stalk-eyed flys amazing eyes-on-stalks. In group displays, males perform near each other and compete for female attention at a traditional breeding display site called a lek. These are often used for generations, as in grouse and great argus pheasant. In clear view, competing males strut, pose, parade, vocalize, throw off scents and perhaps engage in physical tussles.

Attending females assess and compare the males for breeding potential. And, for example, if they choose males with long, showy tails, over many generations those tails may become even longer and showier. This is part of the general evolutionary driver of natural selection known as sexual selection. Well-known examples are peacocks and birds of paradise. However, the extra-long tail may become so heavy, unwieldy and cumbersome that it threatens the males survival. In this way, sexual selection self-limits.

RITUALS AND GROUP ORDER

Courtship and rivalry displays may include ritualized elements. Animal rituals are stereotyped sequences repeated in much the same order each time. The behaviours are often based on actions that the animal does for other reasons, such as self defence or feeding. However, as in the sand lizards head-bobbing, the great crested grebes gift of weed, and the gorillas chest-beating, these actions have become detached from their original survival purpose and incorporated into the ritual.

Ritualized displays can establish dominance or supremacy in a group with an organized hierarchy, such as a wolf pack, tamarin monkey troop or pecking order bird flock. Rivals for status deploy a habitual series of actions and signals. For example, a dominant coyote bares its teeth and growls, while a submissive individual crouches in appeasement. The display avoids serious confrontation and injury, reinforces group order, and is usually over in a couple of seconds. But inevitably there comes a time when the groups alpha boss individual, perhaps ageing, injured or diseased, must face a real challenge.

Animal territories come in many sizes and have diverse functions. They may be the occupiers entire survival locality, with food, shelter and breeding sites. Or they can be a small token of the individuals status and fitness to reproduce, as with a position at the centre of a lek for wire-tailed manakins and blue wildebeest. The incumbent is proclaiming to breeding partners that he is fit, healthy, better than the rest, and ready for successful progeny.