Mobbing in animals is an anti-predator adaptation in which individuals of prey species cooperatively attack or harass a predator, usually to protect their offspring. A simple definition of mobbing is an assemblage of individuals around a potentially dangerous predator. This is most frequently seen in birds, though it is also known to occur in many other animals such as the meerkat 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 may complement cryptic adaptations in the offspring themselves, such as camouflage and hiding. Mobbing calls may be used to summon nearby individuals to cooperate in the attack. Konrad Lorenz, in his book On Aggression (1966), attributed mobbing among birds and animals to instincts rooted in the Darwinian struggle to survive. In his view, humans are subject to similar innate impulses but capable of bringing them under rational control (see: Mobbing).
In birds
Birds that breed in colonies such as gulls 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 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, including advertising their physical fitness and hence uncatchability (much like stotting behavior in gazelles), distracting predators from finding their offspring, warning their offspring, luring the predator away, allowing offspring to 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 for the mobber's young. Niko Tinbergen argued that the mobbing was a source of 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 experimental research, the comparative method can also be employed to investigate hypotheses such as those given by Curio above. For example, not all gull 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 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
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