Mobbing (animal Behavior)
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Mobbing in animals is an
antipredator adaptation Anti-predator adaptations are mechanisms developed through evolution that assist prey organisms in their constant struggle against predators. Throughout the animal kingdom, adaptations have evolved for every stage of this struggle, namely by av ...
in which individuals of prey species
mob Mob or MOB may refer to: Behavioral phenomena * Crowd * Smart mob, a temporary self-structuring social organization, coordinated through telecommunication Crime and law enforcement * American Mafia, also known as the Mob * Irish Mob, a US crim ...
a
predator Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill ...
by cooperatively attacking or harassing it, usually to protect their
offspring In biology, offspring are the young creation of living organisms, produced either by a single organism or, in the case of sexual reproduction, two organisms. Collective offspring may be known as a brood or progeny in a more general way. This ca ...
. A simple definition of mobbing is an assemblage of individuals around a potentially dangerous predator. This is most frequently seen in
birds Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweig ...
, though it is also known to occur in many other
animal Animals are multicellular, eukaryotic organisms in the Kingdom (biology), biological kingdom Animalia. With few exceptions, animals Heterotroph, consume organic material, Cellular respiration#Aerobic respiration, breathe oxygen, are Motilit ...
s such as the
meerkat MeerKAT, originally the Karoo Array Telescope, is a radio telescope consisting of 64 antennas in the Meerkat National Park, in the Northern Cape of South Africa. In 2003, South Africa submitted an expression of interest to host the Square K ...
and some bovines. While mobbing has evolved independently in many species, it only tends to be present in those whose young are frequently preyed upon. This
behavior Behavior (American English) or behaviour ( British English) is the range of actions and mannerisms made by individuals, organisms, systems or artificial entities in some environment. These systems can include other systems or organisms as w ...
may complement
cryptic Cryptic may refer to: In science: * Cryptic species complex, a group of species that are very difficult to distinguish from one another * Crypsis, the ability of animals to blend in to avoid observation * Cryptic era, earliest period of the Earth ...
adaptations in the offspring themselves, such as
camouflage Camouflage is the use of any combination of materials, coloration, or illumination for concealment, either by making animals or objects hard to see, or by disguising them as something else. Examples include the leopard's spotted coat, the b ...
and hiding.
Mobbing calls Mobbing in animals is an antipredator adaptation in which individuals of prey species mob a predator by cooperatively attacking or harassing it, usually to protect their offspring. A simple definition of mobbing is an assemblage of individuals a ...
may be used to summon nearby individuals to cooperate in the attack.
Konrad Lorenz Konrad Zacharias Lorenz (; 7 November 1903 – 27 February 1989) was an Austrian zoologist, ethologist, and ornithologist. He shared the 1973 Nobel Prize in Physiology or Medicine with Nikolaas Tinbergen and Karl von Frisch. He is often rega ...
, in his book '' On Aggression'' (1966), attributed mobbing among birds and animals to
instinct Instinct is the inherent inclination of a living organism towards a particular complex behaviour, containing both innate (inborn) and learned elements. The simplest example of an instinctive behaviour is a fixed action pattern (FAP), in which a ...
s rooted in the
Darwinian Darwinism is a theory of biological evolution developed by the English naturalist Charles Darwin (1809–1882) and others, stating that all species of organisms arise and develop through the natural selection of small, inherited variations that ...
struggle to survive. In his view, humans are subject to similar innate impulses but capable of bringing them under rational control (see
mobbing Mobbing, as a sociological term, means bullying of an individual by a group, in any context, such as a family, peer group, school, workplace, neighborhood, community, or online. When it occurs as physical and emotional abuse in the workplace, ...
).


In birds

Birds that breed in colonies such as
gull Gulls, or colloquially seagulls, are seabirds of the family Laridae in the suborder Lari. They are most closely related to the terns and skimmers and only distantly related to auks, and even more distantly to waders. Until the 21st century, ...
s are widely seen to attack intruders, including encroaching humans. In North America, the birds that most frequently engage in mobbing include mockingbirds, crows and jays, chickadees, terns, and blackbirds. Behavior includes flying about the intruder, dive bombing, loud squawking and defecating on the predator. Mobbing can also be used to obtain food, by driving larger birds and mammals away from a food source, or by harassing a bird with food. One bird might distract while others quickly steal food. Scavenging birds such as gulls frequently use this technique to steal food from humans nearby. A flock of birds might drive a powerful animal away from food. Costs of mobbing behavior include the risk of engaging with predators, as well as energy expended in the process. The
black-headed gull The black-headed gull (''Chroicocephalus ridibundus'') is a small gull that breeds in much of the Palearctic including Europe and also in coastal eastern Canada. Most of the population is migratory and winters further south, but some birds res ...
is a species which aggressively engages intruding predators, such as carrion crows. Classic experiments on this species by Hans Kruuk involved placing hen eggs at intervals from a nesting colony, and recording the percentage of successful predation events as well as the probability of the crow being subjected to mobbing. The results showed decreasing mobbing with increased distance from the nest, which was correlated with increased predation success. Mobbing may function by reducing the predator's ability to locate nests (as a distraction) since predators cannot focus on locating eggs while they are under attack. Besides the ability to drive the predator away, mobbing also draws attention to the predator, making stealth attacks impossible. Mobbing plays a critical role in the identification of predators and inter-generational learning about predator identification. Reintroduction of species is often unsuccessful, because the established population lacks this cultural knowledge of how to identify local predators. Scientists are exploring ways to train populations to identify and respond to predators before releasing them into the wild. Adaptationist hypotheses regarding why an organism should engage in such risky behavior have been suggested by
Eberhard Curio Eberhard Curio (22 October 1932 – 11 September 2020) was a German ecologist, ethologist, and conservation biologist. He was involved in conservation in Southeast Asia, particularly in the Philippines. Curio was educated in Berlin and went in 19 ...
, including advertising their physical fitness and hence uncatchability (much like stotting behavior in gazelles), distracting predators from finding their offspring,
warning Warning may refer to: Signal * Precautionary statement * Warning sign * Warning system * Warning (traffic stop), issued by a police officer in lieu of a citation following a traffic stop Books * A Warning (book), ''A Warning'' (book), a 2019 ...
their offspring, luring the predator away, allowing offspring to
learn Learning is the process of acquiring new understanding, knowledge, behaviors, skills, values, attitudes, and preferences. The ability to learn is possessed by humans, animals, and some machines; there is also evidence for some kind of learn ...
to recognize the predator species, directly injuring the predator or attracting a predator of the predator itself. The much lower frequency of attacks between nesting seasons suggests such behavior may have evolved due to its
benefit Benefit or benefits may refer to: Arts, entertainment and media * ''Benefit'' (album), by Jethro Tull, 1970 * "Benefits" (''How I Met Your Mother''), a 2009 TV episode * ''The Benefit'', a 2012 Egyptian action film Businesses and organisation ...
for the mobber's young.
Niko Tinbergen Nikolaas "Niko" Tinbergen (; ; 15 April 1907 – 21 December 1988) was a Dutch biologist and ornithologist who shared the 1973 Nobel Prize in Physiology or Medicine with Karl von Frisch and Konrad Lorenz for their discoveries concerning the ...
argued that the mobbing was a source of
confusion In medicine, confusion is the quality or state of being bewildered or unclear. The term "acute mental confusion"
to gull chick predators, distracting them from searching for prey . Indeed, an intruding carrion crow can only avoid incoming attacks by facing its attackers, which prevents it from locating its target. Besides
experiment An experiment is a procedure carried out to support or refute a hypothesis, or determine the efficacy or likelihood of something previously untried. Experiments provide insight into cause-and-effect by demonstrating what outcome occurs wh ...
al research, the
comparative method In linguistics, the comparative method is a technique for studying the development of languages by performing a feature-by-feature comparison of two or more languages with common descent from a shared ancestor and then extrapolating backwards ...
can also be employed to investigate hypotheses such as those given by Curio above. For example, not all
gull Gulls, or colloquially seagulls, are seabirds of the family Laridae in the suborder Lari. They are most closely related to the terns and skimmers and only distantly related to auks, and even more distantly to waders. Until the 21st century, ...
species show mobbing behavior. The kittiwake nests on sheer cliffs that are almost completely inaccessible to predators, meaning its young are not at risk of predation like other gull species. This is an example of divergent evolution. Another hypothesis for mobbing behavior is known as the “attract the mightier hypothesis.” Within this hypothesis, prey species produce a mobbing call in order to attract stronger secondary predator to address the threat of the present primary predator. A study conducted by Fang et al., showed significant findings for this unproved functional thesis, utilizing three different call types for the prey species light-vented bulbuls, ''Pycnonotus sinensis'': the typical call (TC, the control treatment), a mobbing call to a collared scops owl (the MtO treatment) and a mobbing call to a crested goshawk, ''Accipiter trivirgatus'' (the superior predator; the MtH treatment). Looking at variation in the behavioural responses of 22 different passerine species to a potential predator, the Eurasian Pygmy Owl, extent of mobbing was positively related with a species prevalence in the owls' diet. Furthermore, the intensity of mobbing was greater in autumn than spring. Mobbing is thought to carry risks to roosting predators, including potential harm from the mobbing birds, or attracting larger, more dangerous predators. Birds at risk of mobbing such as owls have cryptic
plumage Plumage ( "feather") is a layer of feathers that covers a bird and the pattern, colour, and arrangement of those feathers. The pattern and colours of plumage differ between species and subspecies and may vary with age classes. Within species, ...
and hidden roosts which reduces this danger.


Effect of environment on mobbing behavior

Environment has an effect on mobbing behavior as seen in a study conducted by Dagan & Izhaki (2019), wherein mobbing behavior was examined particularly observing the effects of Pine Forest structure. Their findings showed that mobbing behavior varied by season, i.e., high responses in the winter, and moderate response in the fall. Additionally, the presence of a forest understory had a significant impact on mobbing behavior, i.e., the denser the understory vegetation, the more birds responded to mobbing calls. That is to say, the presence of cover in the forest highly contributes to willingness to respond to the aforementioned call.    


In other animals

Another way the comparative method can be used here is by comparing gulls with distantly related organisms. This approach relies on the existence of
convergent evolution Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last com ...
, where distantly related organisms evolve the same trait due to similar
selection pressure Any cause that reduces or increases reproductive success in a portion of a population potentially exerts evolutionary pressure, selective pressure or selection pressure, driving natural selection. It is a quantitative description of the amount of ...
s. As mentioned, many bird species such as the swallows also mob predators, however more distantly related groups including mammals have been known to engage in this behavior. One example is the California ground squirrel, which distracts predators such as the
rattlesnake Rattlesnakes are venomous snakes that form the genera '' Crotalus'' and '' Sistrurus'' of the subfamily Crotalinae (the pit vipers). All rattlesnakes are vipers. Rattlesnakes are predators that live in a wide array of habitats, hunting small ...
and gopher snake from locating their nest
burrow An Eastern chipmunk at the entrance of its burrow A burrow is a hole or tunnel excavated into the ground by an animal to construct a space suitable for habitation or temporary refuge, or as a byproduct of locomotion. Burrows provide a form of s ...
s by kicking sand into their face, which disrupts the snake's sensory organs; for crotaline snakes, this includes the heat-detecting organs in the loreal pits. This
social Social organisms, including human(s), live collectively in interacting populations. This interaction is considered social whether they are aware of it or not, and whether the exchange is voluntary or not. Etymology The word "social" derives from ...
species also uses alarm calls. Some
fish Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% ...
engage in mobbing; for example, bluegills sometimes attack snapping turtles. Bluegills, which form large nesting colonies, were seen to attack both released and naturally occurring turtles, which may advertise their presence, drive the predator from the area, or aid in the transmission of predator recognition. Similarly, humpback whales are known to mob killer whales when the latter are attacking other species, including other cetacean species, seals, sea lions, and fish. There is a distinction though, between mobbing in animals, and
fight-or-flight response The fight-or-flight or the fight-flight-or-freeze response (also called hyperarousal or the acute stress response) is a physiological reaction that occurs in response to a perceived harmful event, attack, or threat to survival. It was first desc ...
. The former relies heavily on group dynamics, whereas the latter’s central focus conceptually is on that of the individual and their offspring in some cases. A study conducted by Adamo & McKee (2017) examining the cricket '' Gryllus texensis'' showcases this by activating high predation risk repeatedly to examine how animals in general perceive such risks. Based on perceived threat, crickets took action to save their own self or made attempt to preserve offspring.


Mobbing calls

Mobbing calls are
signal In signal processing, a signal is a function that conveys information about a phenomenon. Any quantity that can vary over space or time can be used as a signal to share messages between observers. The '' IEEE Transactions on Signal Processing' ...
s made by the mobbing species while harassing a predator. These differ from
alarm call In animal communication, an alarm signal is an antipredator adaptation in the form of signals emitted by social animals in response to danger. Many primates and birds have elaborate alarm calls for warning conspecifics of approaching predato ...
s, which allow con-specifics to ''escape'' from the predator. The great tit, a European
songbird A songbird is a bird belonging to the suborder Passeri of the perching birds ( Passeriformes). Another name that is sometimes seen as the scientific or vernacular name is Oscines, from Latin ''oscen'', "songbird". The Passeriformes contains 50 ...
, uses such a signal to call on nearby birds to harass a perched bird of prey, such as an owl. This call occurs in the 4.5 kHz range, and carries over long distances. However, when prey species are in flight, they employ an alarm signal in the 7–8 kHz range. This call is less effective at traveling great distances, but is much more difficult for both owls and hawks to hear (and detect the direction from which the call came). In the case of the alarm call, it could be disadvantageous to the sender if the predator picks up on the signal, hence
selection Selection may refer to: Science * Selection (biology), also called natural selection, selection in evolution ** Sex selection, in genetics ** Mate selection, in mating ** Sexual selection in humans, in human sexuality ** Human mating strat ...
has favored those birds able to hear and employ calls in this higher frequency range. Furthermore,
Bird vocalization Bird vocalization includes both bird calls and bird songs. In non-technical use, bird songs are the bird sounds that are melodious to the human ear. In ornithology and birding, songs (relatively complex vocalizations) are distinguished by fu ...
s vary acoustically as a byproduct of adapting to the environment, according to the acoustic adaptation hypothesis. In a study by Billings (2018) examining, specifically the low-frequency acoustic structure of mobbing calls across habitat types (closed, open, and urban) in three passerine families (Corvidae, Icteridae, Turdidae), it was discovered that the size of the bird was a factor in the variation of mobbing calls. Additionally, species in closed and urban habitats had lower energy and lower low frequencies in their mobbing calls, respectively. Mobbing calls may also be part of an animal's arsenal in harassing the predator. Studies of '' Phainopepla'' mobbing calls indicate it may serve to enhance the swooping attack on the predators, including scrub jays. In this species, the mobbing call is smoothly upsweeping, and is made when swooping down in an arc beside the predator. This call was also heard during
agonistic behavior Agonistic behaviour is any social behaviour related to fighting. The term has broader meaning than aggressive behaviour because it includes threats, displays, retreats, placation, and conciliation. The term "agonistic behaviour" was first implemen ...
interactions with conspecifics, and may serve additionally or alternatively as an alarm call to their mate.


Evolution

The evolution of mobbing behavior can be explained using evolutionarily stable strategies, which are in turn based on game theory. Mobbing involves risks (costs) to the individual and benefits (payoffs) to the individual and others. The individuals themselves are often genetically related, and mobbing is increasingly studied with the gene-centered view of evolution by considering inclusive fitness (the carrying on of one's genes through one's family members), rather than merely benefit to the individual. Mobbing behavior varies in intensity depending on the perceived threat of a predator according to a study done by Dutour et al. (2016). However, particularly in terms of its surfacing in avian species, it is accepted to be the byproduct of mutualism, rather than reciprocal
altruism Altruism is the moral principle, principle and moral courage, moral practice of concern for the welfare and/or happiness of other human kind, human beings or animals, resulting in a quality of life both material and spirituality, spiritual. It ...
according to Russell & Wright (2009). By cooperating to successfully drive away predators, all individuals involved increase their chances of survival and reproduction. An individual stands little chance against a larger predator, but when a large group is involved, the risk to each group member is reduced or diluted. This so-called dilution effect proposed by W. D. Hamilton is another way of explaining the benefits of cooperation by selfish individuals. Lanchester's laws also provide an insight into the advantages of attacking in a large group rather than individually. Another interpretation involves the use of
signalling theory Within evolutionary biology, signalling theory is a body of theoretical work examining communication between individuals, both within species and across species. The central question is when organisms with conflicting interests, such as in se ...
, and possibly the handicap principle. Here the idea is that a mobbing bird, by apparently putting itself at risk, displays its status and health so as to be preferred by potential partners.


References


External links


Interspecific reciprocity explains mobbing behaviour of the breeding chaffinches, ''Fringilla coelebs''
Paper by Indrikis Krams and Tatjana Krama ( PDF)
Nature Photography
– Using mobbing behavior in
photography Photography is the visual art, art, application, and practice of creating durable images by recording light, either electronically by means of an image sensor, or chemically by means of a light-sensitive material such as photographic film. It i ...

Birds mob Puff Adder
– paper in ejournal Ornithological Observations {{DEFAULTSORT:Mobbing (Animal Behavior) Antipredator adaptations Evolutionary game theory Animal communication Bird behavior