There is little doubt that mobbing behavior has a survival value for animals utilizing it: it creates dangerous situations for the ‘mobber,’ confuses predators, discourages predators through molestation, and even sensitizes escape responses of other prey (Curio et al., 1978). The most widely noted survival value of mobbing behavior is that it decreases the risk of predation by eliciting anti-predator behavior in both parents and nestlings (Suzuki and Ueda, 2013). Not only does mobbing function to decrease predation risk, but it has also been proven to signal predator type (Suzuki and Ueda, 2013). In this section, we will discuss empirical work that has demonstrated how mobbing functions to signal predator type in Japanese Tits and meerkats.
In their study on Japanese Tits (Parus minor), Suzuki and Ueda (2013) tested the hypothesis that a function of mobbing to not only decrease predation risk, but to simultaneously signal predator type. Suzuki and Ueda (2013) observed a total of seven encounters of Japanese Tits in the field for between 2006 and 2012: they observed four encounters with crows and three encounters with snakes. They used a two-tailed Fisher's exact probability test, which is used to compare two nominal variables, to test for acoustic differences in mobbing calls for crows and snakes and found significant results. They were able to show that the Japanese Tits produced a chicka call crows and a jar call for snakes during their encounters (Figure 3).
Figure 3. Differences in mobbing calls of Japanese Tits for crows and snakes: (a) chicka, used to signal the presence of crows, (b) jar, to signal the presence of snakes. As shown above, each of the calls have different frequencies and durations - each are acoustically different to the human ear. As displayed in Suzuki and Ueda (2013).
While mobbing has been extensively studied in birds, there are also a plethora of other studies that focus on its function in other animals. In Graw and Manser’s (2006) study on mobbing behavior in meerkats, they conclude that “mobbing has a broader function beyond predator deterrence, and facilitates situation risk assessment on which subsequent decisions may be based.” They were able to substantiate this by showing that mobbing also occurs in nondangerous situations, which indicates an element of risk assessment. In this case, mobbing is both highly adaptive and a multifunctional behavior, as it functions to deter predators and gather information about potential threats (Graw and Manser, 2006). As shown below, meerkats performed mobbing behavior even in non-dangerous situtations as a form of risk-assessment (Table 1).
Graw and Manser (2006) observed 564 naturally occurring mobbing events in meerkats over a span of 6 years. The mobbed animals ranged in species composition and level of danger. Levels of danger ranged from snakes (mole snake, puff adder, cape cobra), which were the most threatening to meerkats, to tortoises and hares, which were non-threatening to meerkats. Graw and Manser (2006) found that while encounters with dangerous predators such as snakes almost always led to mobbing behavior (90-100% of the time), nondangerous animals such as tortoises and hares were mobbed in 28% of all observed events. As shown below, encounters with nondangerous animals resulted in mobbing 6% of the time (Table 1).
Graw and Manser (2006) observed 564 naturally occurring mobbing events in meerkats over a span of 6 years. The mobbed animals ranged in species composition and level of danger. Levels of danger ranged from snakes (mole snake, puff adder, cape cobra), which were the most threatening to meerkats, to tortoises and hares, which were non-threatening to meerkats. Graw and Manser (2006) found that while encounters with dangerous predators such as snakes almost always led to mobbing behavior (90-100% of the time), nondangerous animals such as tortoises and hares were mobbed in 28% of all observed events. As shown below, encounters with nondangerous animals resulted in mobbing 6% of the time (Table 1).
Table 1. The most frequently mobbed species when encountered by meerkats. While dangerous predators such as the mole snake and Cape cobra were frequently mobbed, this table also shows that mobbing also occurs in nondangerous situations. Taken from Graw and Manser (2006).
There are also many other group benefits of mobbing. These benefits include:
- Harming or deterring a potential predator (detailed above)
- Increasing offspring survivorship
- Discouraging a predator from returning
- Diluting the risk of any one attacker from being predated (Alcock 2005)
- Teaching offspring to recognize predators (Griesser 2009) [discussed in Ontogeny]
- Enlarging territory and associated resources (Gaston 1978)
- Benefits of communal living - foraging efficiency, cooperative kin rearing, increased surveillance (Gaston 1978)