Deception in animals

Deception in animals is the voluntary or involuntary transmission of misinformation by one animal to another, of the same or different species, in a way that misleads the other animal. Robert Mitchell identifies four levels of deception in animals. At the first level, as with protective mimicry like false eyespots and camouflage, the action or display is inbuilt. At the second level, an animal performs a programmed act of behaviour, as when a prey animal feigns death to avoid being eaten. At the third level, the deceptive behaviour is at least partially learnt, as when a bird puts on a distraction display, feigning injury to lure a predator away from a nest. Fourth level deception involves recognition of the other animal's beliefs, as when a chimpanzee tactically misleads other chimpanzees to prevent their discovering a food source.

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.^[2]

Robert Mitchell lists four levels of deception in animals:^[3]

1. First-level deception: an animal acts because it cannot do otherwise, it is programmed to deceive in a certain way. For example, false eyespots 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^[3]
2. Second-level deception: a programmed act of behaviour when another organism is registered. Examples include a predator acting in a way to hide its predatory nature around prey^[3]
3. 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^[3]
4. 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.^[3]

All four levels are found in nature, including bacteria and plants, but the third and fourth levels seem to be exclusive to animals.^[4]

At the first level, an animal acts because it cannot do otherwise, it is programmed to deceive in a certain way. For example, false eyespots such as butterfly markings that indicate their heads are at the back end of their bodies as an aid to escape.^[3]

Mimicry is a resemblance of one species to another which protects one or both species. The can be in visual appearance, behaviour, sound, and scent. There are many types, which can be combined.^[5] Defensive or protective mimicry enables 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 shrimps spread their powerful front limbs 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]

Aggressive mimicry is the mimicking by predators or parasites of harmless species, allowing the predator to approach and sometimes to attract its prey.^[8] Anglerfish are named for their characteristic method of predation. Anglerfish typically have at least one long filament (the illicium) sprouting from the middle of the head, protruding above the fish's eyes and terminating in an irregular growth of flesh (the esca) at the tip of the filament. The filament can move in all directions and the esca can be wiggled so as to resemble a prey animal, thus acting as bait to lure other predators close enough for the anglerfish to devour them.^[8] Some deep-sea anglerfishes of the bathypelagic zone emit light from their escas to attract prey. This bioluminescence is a result of symbiosis with bacteria.^[9][10] Among fireflies, males are lured toward what seems to be a sexually receptive female, only to be eaten. Photuris females emit the same light signals that females of the genus Photinus emit as a mating signal.^[11] Male fireflies from several different genera are attracted to these "femmes fatales" because the predatory females can identify the male's species and emit the signal used by the female of the male's species.^[11]

In automimicry, 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 (Strymon melinus) shows the false head at its rear; it has a better chance of surviving an attack to that part than an attack to the head.^[12]

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). There are many 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 coloured 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 colouration to remain unnoticed during the day. They remain perfectly still, often in a position that increases the effectiveness of their camouflage.^[13][14]

At the second level, an animal conducts a programmed act of behaviour when another organism is registered. Examples include a predator's behaving in such a way as to hide its predatory nature around prey.^[3]

A well-researched form of deception is feigning death, familiarly known 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.^[15]

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.^[16] Birds often feign death to escape predation; for example tonic immobility in quail reduces the probability of attacks by cats.^[17]

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.^[18] In some cases, death feigning is used by a predator. For example, the predatory cichlid Nimbochromis livingstonii 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.^[19]

The third level involves learning, and is based upon trial and error. An example is a distraction display of feigned injury to get or divert attention; for example, a parent mockingbird feigning an injury to attract a predator away from its defenceless offspring.^[3]

Distraction displays, also known as deflection displays and diversionary displays,^[20] are behaviours that draw the attention of a predator away from an object, typically the nest or young.^[21] These are well known in birds, as first described by Aristotle in the 4th century BC,^[22] but also occur in fish.^[23] A familiar example is the broken-wing display seen in nesting waders, plovers and doves such as the mourning dove. In this display, a bird walks away from its nest with one wing dragging on the ground. It seems to be an easy target, thus distracting the predator's attention away from the nest. Once the bird is far enough away it "recovers" and quickly flies off.^[24]

Mitchell^[3] has proposed that self-deception occurs if the deceiver and the object of deception are the same organism. Two approaches are tied to self-deception: intentionalism (self-deception is an intentional act) and revisionism (self-deception is not an intensional act). In both cases, there is a higher-level theory of mind present. Namely, intentionality is tied to the third and fourth level of deception, especially the fourth.^[4] For Mitchell and for Šekrst, intentionality can only be analyzed at the third level, but not as the animal being intentionally deceptive (having recognition of what the other animal effecting that result believes about the action).^[4]

Cases of self-deception have been found in the animal world as well regarding dishonest behaviour of slender crayfish (Cherax dispar).^[25] Šekrst^[4] uses the findings to show that if we consider this case to be a case of self-deception, then we are acknowledging beliefs, in which case we must talk about first-order intentionality and at least Mitchell's third level of deception. Angiletta et al. show that to establish adaptive self-deception, biologists must quantify the cost and benefit of ignoring one's true competitive ability: in this case, deceptive signallers largely ignored their own strength when escalating or evading aggression.^[26]

Angiletta et al. established two conditions for self-deception. First, dishonest individuals must escalate aggression using the same signals that honest individuals do. Second, both dishonest individuals and honest individuals must escalate aggression according to the quality they have signaled, regardless of their actual quality. If both conditions hold, natural selection might have favored genotypes with little or no awareness of their deceptive signaling.^[26]

At the fourth level, deception includes recognition of other animals' beliefs, i.e., second-order thinking, as when a chimpanzee misleads other chimpanzees to prevent their discovering a food source.^[3] This type of deception seems to be prevalent in humans,^[3] but this level also corresponds to the realization of higher-order intentionality.^[4] Tactical or functional deception is the use of signals or displays from an animal's normal repertoire to mislead or deceive another individual.^[27]

• Animal communication
• Deception
• Intentionality
• Mimicry
• Camouflage
• Apparent death
• Distraction display
• Self-deception

• de Waal, Frans B. M. (2 June 2005). "Intentional deception in primates". Evolutionary Anthropology: Issues, News, and Reviews. 1 (3): 86–92. doi:10.1002/evan.1360010306. S2CID 221736130.
• Mitchell, Robert W. (1986). "A framework for discussing deception". In Mitchell, Robert W.; Thompson, Nicholas S. (eds.). Deception, Perspectives on Human and Nonhuman Deceit. SUNY Press. pp. 21–29. ISBN 978-1438413327.
• Osvath, Mathias; Karvonen, Elin (9 May 2012). "Spontaneous Innovation for Future Deception in a Male Chimpanzee". PLOS ONE. 7 (5): e36782. Bibcode:2012PLoSO...736782O. doi:10.1371/journal.pone.0036782. PMC 3348900. 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, Roy; Caldwell, R. L. (5 August 1983). "Intraspecific deception by bluffing: a defense strategy of newly molted stomatopods (arthropoda: crustacea)". Science. 221 (4610): 558–60. Bibcode:1983Sci...221..558S. doi:10.1126/science.221.4610.558. PMID 17830957. S2CID 27223489.
• Šekrst, Kristina (2022). "Everybody lies: deception levels in various domains of life". Biosemiotics. 15 (2): 309–324. doi:10.1007/s12304-022-09485-9. S2CID 250192829.