Mobbing calls signal predator category in a kin group-living bird species

Abstract

Many prey species gather together to approach and harass their predators despite the associated risks. While mobbing, prey usually utter calls and previous experiments have demonstrated that mobbing calls can convey information about risk to conspecifics. However, the risk posed by predators also differs between predator categories. The ability to communicate predator category would be adaptive because it would allow other mobbers to adjust their risk taking. I tested this idea in Siberian jays Perisoreus infaustus, a group-living bird species, by exposing jay groups to mounts of three hawk and three owl species of varying risks. Groups immediately approached to mob the mount and uttered up to 14 different call types. Jays gave more calls when mobbing a more dangerous predator and when in the presence of kin. Five call types were predator-category-specific and jays uttered two hawk-specific and three owl-specific call types. Thus, this is one of the first studies to demonstrate that mobbing calls can simultaneously encode information about both predator category and the risk posed by a predator. Since antipredator calls of Siberian jays are known to specifically aim at reducing the risk to relatives, kin-based sociality could be an important factor in facilitating the evolution of predator-category-specific mobbing calls.

Semantic communication in birds: evidence from field research over the past two decades

“…In the case of Siberian jays, an individual decision to escape from or mob predators depends on behavior of the predators rather than type of predator (Griesser 2008(Griesser , 2009). In the case of Japanese great tits, nestlings are usually within the nest cavities and therefore use two contrasting behaviors to avoid snakes and other predators; that is, they either leave the nest or remain in the nest (Suzuki 2011).…”

The increased risk of predation enhances cooperation

“…This communal defence can cause a predator to vacate its immediate foraging area, which reduces the threat to nearby prey individuals and allows them to resume their daily activities (Flasskamp 1994). Mobbing behaviour is most frequently seen in avian species (Curio 1978;Krams & Krama 2002;Olendorf et al 2004;Templeton et al 2005;Krams et al 2006a;Griesser 2009), although it is also known to occur in other social animals such as mammals, fishes (Kirkwood & Dickie 2005;Solórzano-Filho 2006) and some invertebrates (Mori & Saito 2004). Aside from these benefits, anti-predator behaviours such as mobbing have costs (Montgomerie & Weatherhead 1988;Brunton 1990;Krams et al 2007) and there appears to be a group size effect in mobbing, which indicates the importance of cooperation among prey individuals in driving predators away (Mori & Saito 2004;Krams et al 2009).…”

The anti-predator behaviour of wild white-handed gibbons (Hylobates lar)

“…Morphological adapta-tions include cryptic colouring in Rodentia (Krupa and Geluso 2000), Lepidoptera (Grant 2007), and Squamata (Stuart-Fox et al 2004), and mimicry in Octopoda (Norman et al 2001) and Caudata (Kuchta et al 2008). Behavioural adaptations include warning signals in Passeriformes (Greisser 2009), Sepiida (Langridge et al 2007) and Rodentia (Slobodchikoff and Placer 2006), and predator mobbing in Rodentia (Owings and Coss 1977), Passeriformes (Krams and Krama 2002) and Primates (Eberle and Kappeler 2008).…”