Anti-predator adaptation
Anti-predator adaptations are mechanisms developed through
The first line of defence consists in avoiding detection, through mechanisms such as
Alternatively, prey animals may ward off attack, whether by advertising the presence of strong defences in
Avoiding detection
Staying out of sight
Animals may avoid becoming prey by living out of sight of predators, whether
Camouflage
Camouflage uses any combination of materials, coloration, or illumination for concealment to make the organism hard to detect by sight. It is common in both terrestrial and marine animals. 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.[6][7] Animals such as the flat-tail horned lizard of North America have evolved to eliminate their shadow and blend in with the ground. The bodies of these lizards are flattened, and their sides thin towards the edge. This body form, along with the white scales fringed along their sides, allows the lizards to effectively hide their shadows. In addition, these lizards hide any remaining shadows by pressing their bodies to the ground.[2]
Masquerade
Animals can hide in plain sight by
Apostatic selection
Another way to remain unattacked in plain sight is to look different from other members of the same species. Predators such as
Warding off attack
Many species make use of behavioral strategies to deter predators.[11]
Startling the predator
Many weakly-defended animals, including
Pursuit-deterrent signals
Pursuit-deterrent signals are behavioral signals used by prey to convince predators not to pursue them. For example, gazelles stot, jumping high with stiff legs and an arched back. This is thought to signal to predators that they have a high level of fitness and can outrun the predator. As a result, predators may choose to pursue a different prey that is less likely to outrun them.[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.[16] Warning calls given by birds such as the
Playing dead
Another pursuit-deterrent signal is thanatosis or playing dead. 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. Thanatosis can also be used by the predator in order to lure prey into approaching.[19]
An example of this is seen in white-tailed deer fawns, which experience a drop in heart rate in response to approaching predators. This response, referred to as "alarm bradycardia", causes the fawn's heart rate to drop from 155 to 38 beats per minute within one beat of the heart. This drop in heart rate can last up to two minutes, causing the fawn to experience a depressed breathing rate and decrease in movement, called tonic immobility. Tonic immobility is a reflex response that causes the fawn to enter a low body position that simulates the position of a corpse. Upon discovery of the fawn, the predator loses interest in the "dead" prey. Other symptoms of alarm bradycardia, such as salivation, urination, and defecation, can also cause the predator to lose interest.[20]
Distraction
Marine
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.[25]
Mimicry and aposematism
In Batesian mimicry, a palatable, harmless prey species mimics the appearance of another species that is noxious to predators, thus reducing the mimic's risk of attack.[27] This form of mimicry is seen in many insects. 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.[29][30] Some species of octopus can mimic a selection of other animals by changing their skin color, skin pattern and body motion. When a damselfish attacks an octopus, the octopus mimics a banded sea-snake.[31] The model chosen varies with the octopus's predator and habitat.[32] Most of these octopuses use Batesian mimicry, selecting an organism repulsive to predators as a model.[33][34]
In
Defensive structures
Many animals are protected against predators with armour in the form of hard shells (such as most
A spine is a sharp, needle-like structure used to inflict pain on predators. An example of this seen in nature is in the sohal surgeonfish. These fish have a sharp scalpel-like spine on the front of each of their tail fins, able to inflict deep wounds. The area around the spines is often brightly colored to advertise the defensive capability;[36] predators often avoid the Sohal surgeonfish.[37] Defensive spines may be detachable, barbed or poisonous. Porcupine spines are long, stiff, break at the tip, and in some species are barbed to stick into a would-be predator. 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.[37]
Many species of slug caterpillar, Limacodidae, have numerous protuberances and stinging spines along their dorsal surfaces. Species that possess these stinging spines suffer less predation than larvae that lack them, and a predator, the paper wasp, chooses larvae without spines when given a choice.[39]
Safety in numbers
Group living can decrease the risk of predation to the individual in a variety of ways,[40] as described below.
Dilution effect
A dilution effect is seen when animals living in a group "dilute" their risk of attack, each individual being just one of many in the group.
Selfish herd
The selfish herd theory was proposed by
Predator satiation
A radical strategy for avoiding predators which may otherwise kill a large majority of the emerging stage of a population is to emerge very rarely, at irregular intervals. Predators with a life-cycle of one or a few years are unable to reproduce rapidly enough in response to such an emergence. Predators may feast on the emerging population, but are unable to consume more than a fraction of the brief surfeit of prey. 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.[45]
Alarm calls
Animals that live in groups often give alarm calls that give warning of an attack. 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". The monkeys hearing these calls respond defensively, but differently in each case: to the eagle call, they look up and run into cover; to the leopard call, they run up into the trees; to the snake call, they stand on two legs and look around for snakes, and on seeing the snake, they sometimes mob it. Similar calls are found in other species of monkey, while birds also give different calls that elicit different responses.[46]
Improved vigilance
In the improved vigilance effect, groups are able to detect predators sooner than solitary individuals.[47] For many predators, success depends on surprise. If the prey is alerted early in an attack, they have an improved chance of escape. For example, wood pigeon flocks are preyed upon by goshawks. Goshawks are less successful when attacking larger flocks of wood pigeons than they are when attacking smaller flocks. This is because the larger the flock size, the more likely it is that one bird will notice the hawk sooner and fly away. Once one pigeon flies off in alarm, the rest of the pigeons follow.[48] Wild ostriches in Tsavo National Park in Kenya feed either alone or in groups of up to four birds. They are subject to predation by lions. As the ostrich group size increases, the frequency at which each individual raises its head to look for predators decreases. Because ostriches are able to run at speeds that exceed those of lions for great distances, lions try to attack an ostrich when its head is down. By grouping, the ostriches present the lions with greater difficulty in determining how long the ostriches' heads stay down. Thus, although individual vigilance decreases, the overall vigilance of the group increases.[49]
Predator confusion
Individuals living in large groups may be safer from attack because the predator may be confused by the large group size. As the group moves, the predator has greater difficulty targeting an individual prey animal. The
Fighting back
Defensive structures such as spines may be used both to ward off attack as already mentioned, and if need be to fight back against a predator.[37] Methods of fighting back include chemical defences,[51] mobbing,[52] defensive regurgitation,[53] and suicidal altruism.[54]
Chemical defences
Many prey animals, and to defend against
Some prey animals are able to eject noxious materials to deter predators actively. The
A few vertebrate species such as the Texas horned lizard are able to shoot squirts of blood from their eyes, by rapidly increasing the blood pressure within the eye sockets, if threatened. 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.[64] Canids often drop horned lizards after being squirted, and attempt to wipe or shake the blood out of their mouths, suggesting that the fluid has a foul taste;[65] they choose other lizards if given the choice,[66] suggesting a learned aversion towards horned lizards as prey.[66]
The slime glands along the body of the hagfish secrete enormous amounts of mucus when it is provoked or stressed. The gelatinous slime has dramatic effects on the flow and viscosity of water, rapidly clogging the gills of any fish that attempt to capture hagfish; predators typically release the hagfish within seconds. Common predators of hagfish include seabirds, pinnipeds and cetaceans, but few fish, suggesting that predatory fish avoid hagfish as prey.[67]
Communal defence
In communal defence, prey groups actively defend themselves by grouping together, and sometimes by attacking or mobbing a predator, rather than allowing themselves to be passive victims of predation.
Defensive regurgitation
Some birds and insects use defensive regurgitation to ward off predators. The northern fulmar vomits a bright orange, oily substance called stomach oil when threatened.[53] The stomach oil is made from their aquatic diets. It causes the predator's feathers to mat, leading to the loss of flying ability and the loss of water repellency.[53] This is especially dangerous for aquatic birds because their water repellent feathers protect them from hypothermia when diving for food.[53]
European roller chicks vomit a bright orange, foul smelling liquid when they sense danger. This repels prospective predators and may alert their parents to danger: they respond by delaying their return.[69]
Numerous insects utilize defensive regurgitation. The
Suicidal altruism
An unusual type of predator deterrence is observed in the
Escaping
Flight
The normal reaction of a prey animal to an attacking predator is to flee by any available means, whether flying, gliding,
Autotomy
Some animals are capable of autotomy (self-amputation), shedding one of their own appendages in a last-ditch attempt to elude a predator's grasp or to distract the predator and thereby allow escape. The lost body part may be regenerated later. Certain sea slugs discard stinging papillae; arthropods such as crabs can sacrifice a claw, which can be regrown over several successive moults; among vertebrates, many geckos and other lizards shed their tails when attacked: the tail goes on writhing for a while, distracting the predator, and giving the lizard time to escape; a smaller tail slowly regrows.[77]
History of observations
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.[78]
In 1940,
By the 21st century, adaptation to life in
See also
- Ecology of fear (concept)– Psychological impact induced by predators
- Plant defense against herbivory – Plants' defenses against being eaten
References
- PMID 22355648.
- ^ a b Sherbrooke, W. C. (2003). Introduction to horned lizards of North America. University of California Press. pp. 117–118.
- ^ Cott, H.B. (1940). Adaptive Coloration in Animals. London: Methuen. pp. 330–335.
- ^ .
- ^ S2CID 4077513.
- ^ a b Cott 1940.
- ^ Caro 2005, pp. 35–60.
- ^ Caro 2005, pp. 53–55.
- ^ Cott 1940, pp. 318–320.
- ^ Caro 2005, pp. 61–65.
- ^ Cooper, William E. "Antipredatory Behavior". IDEA. University of California, Riverside. Archived from the original on 18 May 2018. Retrieved 23 October 2014.
- S2CID 24868603.
- ^ Edmunds, Malcolm (2012). "Deimatic Behavior". Springer. Retrieved 31 December 2012.
- ^ Smith, Ian (3 December 2012). "Octopus vulgaris. Dymantic display". The Conchological Society of Great Britain and Ireland. Retrieved 1 January 2013.
- S2CID 53155678.
- S2CID 83504795.
- S2CID 2295026.
- S2CID 53164940.
- .
- S2CID 7739227.
- ^ a b Inman, Mason (29 March 2005). "Sea Hares Lose Their Lunch". Sciencemag.org. Archived from the original on 2021-09-24. Retrieved 10 May 2015.
- S2CID 9539618.
- S2CID 92064. Archived from the original(PDF) on 15 November 2009. Retrieved 9 May 2015.
- ISBN 978-0-8493-2005-7.
- ^ a b Ruxton, Sherratt & Speed 2004, p. 198.
- .
- ^ .
- ^ S2CID 13436225.
- .
- ^ Stearns, Stephen; Hoekstra, Rolf (2005). Evolution: An Introduction. Oxford University Press. p. 464.
- PMID 11522192.
- .
- S2CID 8153271.
- PMID 11522192.
- ^ Müller, Fritz (1879). "Ituna and Thyridia; a remarkable case of mimicry in butterflies. (R. Meldola translation.)". Proclamations of the Entomological Society of London. 1879: 20–29.
- ^ Thomas, Craig. Scott, Susan. (1997). All Stings Considered. University of Hawaii Press. pp. 96–97.
- ^ .
- ISBN 978-1-78023-315-4.
- .
- ^ Edmunds 1974, pp. 202–207.
- S2CID 53154054.
- S2CID 4365789.
- PMID 5104951.
- PMID 19793737.
- .
- ISBN 978-0-19852-685-8.
- ^ Caro 2005, pp. 115–149.
- PMID 4734745.
- S2CID 53144763.
- PMID 22117898.
- ^ a b c Ruxton, Sherratt & Speed 2004, pp. 64–69.
- ^ .
- ^ a b c d Warham, John (1977). "The Incidence, Functions and Ecological Significance of Petrel Stomach Oils" (PDF). New Zealand Ecological Society. 24: 84–93.
- ^ S2CID 13257903.
- ^ )
- ^ a b Edmunds 1974, pp. 189–201.
- .
- Discover Magazineblog, 28 July 2009, retrieved 17 March 2010
- ^ .
- PMID 15339944.
- ^ Mayell, Hillary (February 10, 2005). "Cobras Spit Venom at Eyes With Nearly Perfect Aim". National Geographic. Archived from the original on November 10, 2005.
- ISBN 9780674000896.
- .
- JSTOR 1446212.
- ^ Pianka, Erika R. & Wendy L. Hodges. "Horned Lizards". University of Texas. Archived from the original on 29 April 2011. Retrieved 18 November 2013.
- ^ S2CID 55365586.
- PMID 16449564.
- S2CID 53195968.
- PMID 23874791.
- JSTOR 1939211.)
{{cite journal}}
: CS1 maint: multiple names: authors list (link - doi:10.1155/1993/67950.)
{{cite journal}}
: CS1 maint: multiple names: authors list (link - S2CID 23756265.
- ^ ISBN 978-1444332551.
- ISBN 978-1-135-07607-8.
- ^ Kruszelnicki, Karl S. (August 9, 1999). "Real Wheel Animals—Part Two". Great Moments in Science. ABC Science. Archived from the original on October 1, 2016.
- ^ a b c d Edmunds 1974, pp. 145–149.
- ^ Edmunds 1974, pp. 179–181.
- ^ Aristotle (1910) [350 BC]. The History of Animals. Vol. IX. pp. 621b–622a.
- S2CID 221864354.
Sources
- Caro, Tim (2005). Antipredator Defenses in Birds and Mammals. University of Chicago Press.
- Cott, Hugh (1940). Adaptive Coloration in Animals. Oxford University Press.
- Edmunds, Malcolm (1974). Defence in Animals. Longman.
- Ruxton, Graeme D.; Sherratt, Thomas N.; Speed, Michael P. (2004). Avoiding Attack: The Evolutionary Ecology of Crypsis, Warning Signals and Mimicry. Oxford.