Anti-predator adaptation

Throughout the animal kingdom, adaptations have evolved for every stage of this struggle, namely by avoiding detection, warding off attack, fighting back, or escaping when caught.

The first line of defence consists in avoiding detection, through mechanisms such as camouflage, masquerade, apostatic selection, living underground, or nocturnality.

[5] Camouflage uses any combination of materials, coloration, or illumination for concealment to make the organism hard to detect by sight.

Camouflage can be achieved in many different ways, such as through resemblance to surroundings, disruptive coloration, shadow elimination by countershading or counter-illumination, self-decoration, cryptic behavior, or changeable skin patterns and colour.

For example, the potoo, a South American bird, habitually perches on a tree, convincingly resembling a broken stump of a branch,[8] while a butterfly, Kallima, looks just like a dead leaf.

[15] White-tailed deer and other prey mammals flag with conspicuous (often black and white) tail markings when alarmed, informing the predator that it has been detected.

Thanatosis is a form of bluff in which an animal mimics its own dead body, feigning death to avoid being attacked by predators seeking live prey.

[20]Marine molluscs such as sea hares, cuttlefish, squid and octopuses give themselves a last chance to escape by distracting their attackers.

[21][23] Distraction displays attract the attention of predators away from an object, typically the nest or young, that is being protected,[24] as when some birds feign a broken wing while hopping about on the ground.

The idea behind Batesian mimicry is that predators that have tried to eat the unpalatable species learn to associate its colors and markings with an unpleasant taste.

This results in the predator learning to avoid species displaying similar colours and markings, including Batesian mimics, which are in effect parasitic on the chemical or other defences of the unprofitable models.

[28] Many animals are protected against predators with armour in the form of hard shells (such as most molluscs and turtles), leathery or scaly skin (as in reptiles), or tough chitinous exoskeletons (as in arthropods).

The area around the spines is often brightly colored to advertise the defensive capability;[36] predators often avoid the Sohal surgeonfish.

In contrast, the hedgehog's short spines, which are modified hairs,[38] readily bend, and are barbed into the body, so they are not easily lost; they may be jabbed at an attacker.

Experiments provide direct evidence for the decrease in individual attack rate seen with group living, for example in Camargue horses in Southern France.

Testing Hamilton's selfish herd effect, Alta De Vos and Justin O'Rainn (2010) studied brown fur seal predation from great white sharks.

Periodical cicadas, which emerge at intervals of 13 or 17 years, are often used as an example of this predator satiation, though other explanations of their unusual life-cycle have been proposed.

For example, vervet monkeys give different calls depending on the nature of the attack: for an eagle, a disyllabic cough; for a leopard or other cat, a loud bark; for a python or other snake, a "chutter".

Furthermore, when moving rapidly, the zebra stripes create a confusing, flickering motion dazzle effect in the eye of the predator.

[51][56] These may be concentrated in surface structures such as spines or glands, giving an attacker a taste of the chemicals before it actually bites or swallows the prey animal: many toxins are bitter-tasting.

Many insects acquire toxins from their food plants; Danaus caterpillars accumulate toxic cardenolides from milkweeds (Asclepiadaceae).

[58] Several species of grasshopper including Poecilocerus pictus,[59] Parasanaa donovani,[59] Aularches miliaris,[59] and Tegra novaehollandiae secrete noxious liquids when threatened, sometimes ejecting these forcefully.

[59] Spitting cobras accurately squirt venom from their fangs at the eyes of potential predators,[60] striking their target eight times out of ten, and causing severe pain.

[61] Termite soldiers in the Nasutitermitinae have a fontanellar gun, a gland on the front of their head which can secrete and shoot an accurate jet of resinous terpenes "many centimeters".

[62] Seeds deter predation with combinations of toxic non-protein amino acids, cyanogenic glycosides, protease and amylase inhibitors, and phytohemagglutinins.

Because an individual may lose up to 53% of blood in a single squirt,[63] this is only used against persistent predators like foxes, wolves and coyotes (Canidae), as a last defence.

[76] Escape paths are often erratic, making it difficult for the predator to predict which way the prey will go next: for example, birds such as snipe, ptarmigan and black-headed gulls evade fast raptors such as peregrine falcons with zigzagging or jinking flight.

[73] Among the insects, many moths turn sharply, fall, or perform a powered dive in response to the sonar clicks of bats.

[76] Among fish, the stickleback follows a zigzagging path, often doubling back erratically, when chased by a fish-eating merganser duck.

[77] Aristotle recorded observations (around 350 BC) of the antipredator behaviour of cephalopods in his History of Animals, including the use of ink as a distraction, camouflage, and signalling.