Deception in animals
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Deception in animals is the transmission of misinformation by one animal to another, of the same or different species, in a way that propagates beliefs that are not true.
Mimicry and camouflage enable animals to appear to be other than they are. Prey animals may appear as predators, or vice versa; both predators and prey may be hard to see (crypsis), or may be mistaken for other objects (mimesis). In Batesian mimicry, harmless animals may appear to be distasteful or poisonous. In automimicry, animals may have eyespots in less important parts of the body than the head, helping to distract attack and increase the chance of survival.
In more active forms of anti-predator adaptation, animals may feign death when they detect a predator, or may quickly conceal themselves or take action to distract a predator, such as when a cephalopod releases ink. In deimatic behaviour, a harmless animal adopts a threatening pose or displays startling, brightly coloured parts of its body to startle a predator or rival.
Some animals may use tactical deception, with behaviour that is deployed in a way that other animals misinterpret what is happening to the advantage of the agent. Some of the evidence for this is anecdotal, but in the
Overview
Some types of deception in animals are completely involuntary (e.g. disruptive coloration), but others are under voluntary control and may involve an element of learning. Most instances of voluntary deception in animals involve a simple behaviour, such as a cat arching its back and raising its hackles, to make itself appear larger than normal when attacked. There are relatively few examples of animal behaviour which might be attributed to the manipulative type of deception which we know occurs in humans, i.e. "tactical deception". It has been argued that true deception assumes the deceiver knows that (1) other animals have minds, (2) different animals' minds can believe different things are true (when only one of these is actually true), and (3) it can make another mind believe that something false is actually true. True deception requires the deceiver to have the mental capacity to assess different representations of reality. Animal behaviour scientists are therefore wary of interpreting a single instance of behaviour as true deception, and explain it with simpler mental processes such as learned associations.[1] In contrast, human activities such as military deception are certainly intentional, even when they involve methods such as camouflage which physically parallel camouflage methods used by animals.
Levels of deception in animals
Mitchell lists four levels of deception in animals:[2]
- First-level deception: an animal acts because it cannot do otherwise, it is programmed to deceive in a certain way. For example, false eyeballs on animals, such as butterfly markings that indicate their heads are at the back end of their bodies as an aid to escape, or markings to make predators appear safe[2]
- Second-level deception: a programmed act of behavior when another organism is registered. Examples include a predator acting in a way to hide its predatory nature around prey[2]
- Third-level deception: involves learning, and is based upon trial and error. An example is feigned injury to get or divert attention; for example, a parent mockingbird feigning an injury to attract a predator away from its defenceless offspring[2]
- Fourth-level deception: includes recognition of other animals' beliefs, i.e., second-order thinking. This can be verbal deception such as a chimp misleading other chimps to hide a food source. [2]
All four levels are found in the biological world, including bacteria and plants, but the third level and fourth level seem to be exclusive to animals.[3] Cases of self-deception have been found in the animal world as well regarding dishonest behavior of slender crayfish (Cherax dispar).[4]
One of the most common levels of deception is the first level of deception:
Defensive mimicry
Defensive or protective mimicry takes place when organisms are able to avoid encounters that would be harmful to them by deceiving enemies by appearing to be something that they are not. For example, mantis shrimp typically spread their front limbs (known as "smashers") to threaten rivals in a behaviour called the "meral spread".[6] Newly moulted mantis shrimps frequently deceive potential competitors by spreading their front limbs, even though their still-soft exoskeletons meant that they could not use their smashers without damaging themselves.[7][6]
Batesian mimicry
Batesian mimicry is a form of mimicry typified by a situation where a harmless species has evolved to imitate the
Examples of Batesian mimicry are the several species of butterflies that mimic the toxic
Deception by Batesian mimicry need not be visual, as it may involve any of the
Müllerian mimicry
Müllerian mimicry occurs when two or more genuinely unprofitable species have come to mimic each other's warning signals, so unlike the case in Batesian mimicry, no deception is involved. Typically the species share one or more common predators, though they may or may not be closely related.[11]
For example, the
Müllerian mimicry may also use any of the senses. For example, many snakes share the same
Aggressive mimicry
Aggressive mimicry is the mimicking by predators or
Several turtle species and the frogmouth catfish have tongue extensions that lure prey to a position where they become an easy catch.[12] In sal luring, the predator uses tail movements to attract prey. This form of mimicry is used by several snake and species,such as the spider-tailed horned viper which tail deceits a spider, thus attracting birds, tasselled wobbegong shark is as well an example.
In another example of aggressive mimicry, males are lured toward what seems to be a
Aggressive mimicry need not involve the sense of vision. For example, the
Automimicry
Automimicry refers to instances in which one body part of an animal mimics another. This may help and animal survive an attack, or help predators to appear innocuous. Examples include many moth, butterfly, and fish species that have "eye-spots". These are large dark markings that help prey escape by causing predators to attack a false target. For example, the gray hairstreak (
Camouflage
Camouflage is the use of any combination of materials, coloration, or behaviour that helps to conceal an animal by making it hard to see (crypsis) or by disguising it as something else (mimesis).
Crypsis
There are several methods of achieving crypsis. These include, resemblance to the surroundings, disruptive coloration, eliminating shadow, self-decoration, cryptic behaviour, motion camouflage, changeable skin appearance, countershading, counter-illumination, transparency, and silvering to reflect the environment.
Many species are cryptically colored to resemble their surroundings. For example, Uroplatus geckos can be almost completely invisible, even to a nearby observer. Similarly, the katydids, a group of grasshopper-like insects found worldwide, are nocturnal and use their cryptic coloration to remain unnoticed during the day. They remain perfectly still, often in a position that increases the effectiveness of their camouflage.
Some animals have coloration which makes them highly conspicuous when outside their normal environment but highly cryptic when in it. For example, the blue
Underwater animals adopt a wide range of methods of camouflage including transparency, reflection, counter-illumination, countershading, and self-decoration. Fish are light on the bottom and dark on top to blend into the background when viewed from top or bottom.
Most forms of camouflage are less effective when the camouflaged animal moves because motion is easily seen by the observing predator or prey.
Mimesis
Katydids have evolved a wide range of camouflage adaptations so their body colouring and shape match entire leaves, half-eaten leaves, dying leaves, leaves with bird droppings, sticks, twigs, and tree bark. Other well-known mimetic animals include
, and fish.A well known response of cephalopods when threatened is to release large volumes of ink. Some cephalopods also release pseudomorphs ("false bodies"); smaller clouds of ink with a greater mucus content, which allows them to hold their shape for longer. These are expelled slightly away from the cephalopod; they are roughly the same volume and look like the cephalopod that released them. Predators have often been seen attacking a pseudomorph, allowing the cephalopod to escape.
Active camouflage
There are two mechanisms of active camouflage in animals: counter-illumination and colour change (sometimes called metachrosis).
In counter-illumination camouflage an animal produces light that causes it to blend in against a lit background. In water, light comes down from the surface, so when animals are seen from below, they appear darker than the background. Some species of cephalopod, such as the
Colour change permits camouflage against different backgrounds. In the context of deception, this can be used as a defence or predatory strategy, or during courtship and mating. Colour change is made possible by
Some
Some octopuses can use muscles in the skin to change both the colour and texture of their
Feigning death
A well-researched form of deception is feigning death, often referred to by non-specialists as "playing dead" or "playing possum", although specialists use the terms "tonic immobility" or "thanatosis". A wide range of animals, e.g. lizards, birds, rodents, and sharks, behave as if dead as an anti-predator adaptation, as predators usually take only live prey.[29]
In beetles, artificial selection experiments have shown that there is heritable variation for length of death-feigning. Those selected for longer death-feigning durations are at a selective advantage to those at shorter durations when a predator is introduced.[30] Birds often feign death to escape predation; for example tonic immobility in quail reduces the probability of attacks by cats.[31]
Death feigning may also play a role in reproduction, for example, in the nursery web spider, the male sometimes feigns death to avoid getting eaten by females during mating.[32] In some cases, death feigning is used by a predator. For example, the predatory cichlid Haplochromis livingstoni lies on its side on the bottom sediments until approached by scavengers attracted to what appears to be a dead fish, whereupon H. livingstoni abandons the pretence, rights itself and attacks the scavenger.[33]
Death feigning behaviour can be deliberately induced by humans, a prominent example being the "hypnosis" of chickens or pigeons. For example, if a pigeon is grasped firmly, quickly inverted and held briefly on its back on a table, it often remains immobile for a minute or two. According to Gilman et al.
Concealment
Many animals hide from predators behind rocks, in holes, in brush, and in many other ways. Some actually carry around parts of the environment to use for that purpose. For example,
Cephalopods also conceal themselves by releasing large amounts of dark ink when they are threatened. The ink obscures the vision of the threatening animal and allows the cephalopod to escape.
Distraction displays
Distraction displays, also known as deflection displays and diversionary displays,
Deimatic displays
A deimatic displays is a pattern of threatening or startling behaviour, such as suddenly displaying conspicuous eyespots, used to scare off or momentarily distract a predator, thus giving the prey animal an opportunity to escape. For example, some moths look threatening while at rest by displaying a sinister lurking face, such as those of genus Speiredonia, or the more aggressive face of a snake poised to attack, such as many species of genus Spirama. Adult Atlas moths of the genera Attacus and Rothschildia also display snake heads.[47] The eyed hawkmoth displays its large eyespots on its wings and moves them slowly as if it were a vertebrate predator such as an owl.[48]
Tactical deception
Tactical deception (also referred to as functional deception) is the use of signals or displays from an animal's normal repertoire to mislead or deceive another individual.[49] Some researchers limit the use of this term to an intraspecific[50] behaviour, meaning that it occurs between members of the same species. Most other kinds of deception are meant to fool members of a different species. Tactical deception can also be achieved when the deceiver withholds information by failing to perform an expected action, such as giving a warning call when danger is observed.
Tactical deception can be costly to the user, because it occurs mostly in social animals that may lose trust in a group-member when that member's deceit is discovered. Indeed, a notable view in ethology is that animal displays are usually accurate signals, and that widespread deception cannot become a stable feature of a communication system. In this view, widespread use of deception would cause communication to break down, as the recipients of false signals would become "skeptical" about signal validity in general and fail to respond appropriately. However, as exemplified below, limited use of deception does seem to be a stable feature in various communities.
It is unclear what cognitive abilities are necessary for an animal to exhibit tactical deception. It might require the ability to understand another animal's point of view, or it might require only the use of specialized learned behaviours. These alternatives are hotly debated, and the answer tends to vary depending on the species being observed. In the first scenario, the deceiver would need a
Tactical deception has been used as a measure of advanced social cognition as it relates to brain function. Primates have larger brains, relative to body size, than in any other mammal except for
Among
In domestic pigs, in a setting where the behavior of a trained animal could reveal the source of food to another animal, the trained animal spent longer at the food source before other pigs arrived.[53]
In an anecdotal account, Simmons[54] reported that a female marsh harrier courted a male to obtain access to food he had stored. She then took this food and fed it to chicks that had been fathered by another male. More extensive studies focused on possibly deceitful behaviour in the pied flycatcher, a species in which males may possess more than one territory. Females gain from mating with a male that has no other mates and males may try to deceive females about their mating status (mated or unmated). Females frequently visit the male, and if he is always alone on his territory he is probably unmated. Thus, by repeated sampling of male behaviour, females are usually able to avoid mating with previously mated males.[55]
Group-foraging
Observations on great apes have been widely reported as evidence of tactical deception. Several great apes have been trained to use sign language, and in some instances these animals seem to have used language in an attempt to deceive human observers.
Another example involves a chimpanzee that was approached from behind by a loud aggressive rival. Here, the chimpanzee moved his lips until he lost his fear grin thereby concealing his fear. Only then did he turn around to face the challenger.[49][60][61]
Deceit in great apes has been studied under experimental conditions, one of which is summarised by Kirkpatrick:[61]
- "...food was hidden and only one individual, named Belle, in a group of chimpanzees was informed of the location. Belle was eager to lead the group to the food but when one chimpanzee, named Rock, began to refuse to share the food, Belle changed her behaviour. She began to sit on the food until Rock was far away, then she would uncover it quickly and eat it. Rock figured this out though and began to push her out of the way and take the food from under her. Belle then sat farther and farther away waiting for Rock to look away before she moved towards the food. In an attempt to speed the process up, Rock looked away until Belle began to run for the food. On several occasions he would even walk away, acting disinterested, and then suddenly spin around and run towards Belle just as she uncovered the food."
Deceptive behaviour has been observed in
Among New World monkeys, Tufted capuchin (Cebus apella) monkey subordinates have been found to employ a vocal form of tactical deception when competing with dominant monkeys over valuable food resources. They use alarm calls normally reserved for predator sightings— either barks (used specifically for aerial stimuli), peeps, or hiccups— to elicit a response in fellow group members and then take advantage of the distraction to pilfer food. In a series of experiments directed by Brandon Wheeler a group of tufted capuchin monkeys was provided with bananas on feeding platforms. Here, subordinate monkeys made nearly all of the alarm calls that could be classified as "false", and in many of the false alarms, the caller was on or within two meters of the feeding platform. The calls made dominant monkeys leave the platform while the subordinate caller stayed behind to eat.[62]
Costs of tactical deception
Withholding information, a form of tactical deception, can be costly to the deceiver. For example, rhesus monkeys discovering food announce their discoveries by calling on 45% of occasions. Discoverers who fail to call, but are detected with food by other group members, receive significantly more aggression than vocal discoverers. Moreover, silent female discoverers eat significantly less food than vocal females.[63] Presumably because of such costs to deceivers, tactical deception occurs rather rarely. It is thought to be more common in forms and species where the cost of ignoring the possibly deceptive act is even higher than the cost of believing. For example, tufted capuchin monkeys sometimes emit false alarm calls. The cost of ignoring one of these calls could be death, which may lead to a "better safe than sorry" philosophy even when the caller is a known deceiver.[62]
See also
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Further reading
- de Waal, Frans B. M. (2 June 2005). "Intentional deception in primates". Evolutionary Anthropology: Issues, News, and Reviews. 1 (3): 86–92. S2CID 221736130.
- Osvath, Mathias; Karvonen, Elin (9 May 2012). "Spontaneous Innovation for Future Deception in a Male Chimpanzee". PLOS ONE. 7 (5): e36782. PMID 22590606.
- Searcy, William A.; Nowicki, Stephen (2005). The Evolution of Animal Communication Reliability and Deception in Signaling Systems. Princeton University Press. ISBN 9781400835720.
- Steger, R.; Caldwell, R. L. (5 August 1983). "Intraspecific deception by bluffing: a defense strategy of newly molted stomatopods (arthropoda: crustacea)". Science. 221 (4610): 558–60. S2CID 27223489.