Mobbing calls signal predator category in a kin group-living bird species (original) (raw)
Related papers
Referential calls signal predator behavior in a group-living bird species
Current Biology, 2008
Predation is a powerful agent of natural selection, driving the evolution of antipredator calls [1]. These calls have been shown to communicate predator category and/or predator distance to conspecifics . However, the risk posed by predators depends also on predator behavior , and the ability of prey to communicate predator behavior to conspecifics would be a selective advantage reducing their predation risk. I tested this idea in Siberian jays (Perisoreus infaustus), a group-living bird species. Predation by hawks, and to a lesser extent by owls, is substantial and the sole cause of mortality in adult jays . By using field data and predator-exposure experiments, I show here that jays used antipredator calls for hawks depending on predator behavior. A playback experiment demonstrated that these prey-to-prey calls were specific to hawk behavior (perch, prey search, attack) and elicited distinct, situation-specific escape responses. This is the first study to demonstrate that prey signals convey information about predator behavior to conspecifics. Given that antipredator calls in jays aim at protecting kin group members , consequently lowering their mortality [9], kin-selected benefits could be an important factor for the evolution of predator-behavior-specific antipredator calls in such systems.
Referential calls coordinate multi-species mobbing in a forest bird community
Japanese great tits (Parus minor) use a sophisticated system of anti-predator communication when defending their offspring: they produce different mobbing calls for different nest predators (snake versus non-snake predators) and thereby convey this information to con-specifics (i.e. functionally referential call system). The present playback experiments revealed that these calls also serve to coordinate multi-species mobbing at nests; snake-specific mobbing calls attracted heterospecific individuals close to the sound source and elicited snake-searching behaviour, whereas non-snake mobbing calls attracted these birds at a distance. This study demonstrates for the first time that referential mobbing calls trigger different formations of multi-species mobbing parties.
Caller characteristics influence recruitment to collective anti-predator events in jackdaws
Scientific Reports, 2018
Across the animal kingdom, examples abound of individuals coming together to repel external threats. When such collective actions are initiated by recruitment signals, individuals may benefit from being selective in whom they join, so the identity of the initiator may determine the magnitude of the group response. However, the role of signaller discrimination in coordinating group-level responses has yet to be tested. Here we show that in wild jackdaws, a colonial corvid species, collective responses to anti-predator recruitment calls are mediated by caller characteristics. In playbacks next to nestboxes, the calls of nestbox residents attracted most recruits, followed in turn by other colony members, noncolony members and rooks (a sympatric corvid). Playbacks in fields outside nestbox colonies, where the immediate threat to broods was lower, showed similar results, with highest recruitment to nearby colony members' calls. Responses were further influenced by caller sex: calls from non-colony member females were less likely to elicit responsive scolding by recruits than other calls, potentially reflecting social rank associated with sex and colony membership. These results show that vocal discrimination mediates jackdaws' collective responses and highlight the need for further research into the cognitive basis of collective actions in animal groups. From army ants to human armies, groups of conspecifics across many taxa exhibit collective responses towards external threats, often in response to specific recruitment signals 1-4. The success of defensive groups is likely to be closely linked to their size 5 , so it is important to understand the processes that determine the magnitude of collective responses. Group defences often present collective action problems, in which individuals face conflicting incentives when deciding whether to join 6,7. In anti-predator mobbing, for example, joining a mob can provide a collective benefit by helping to drive away a potentially lethal threat 8,9 , and individuals may also benefit from gathering information about the predator 2,3. On the other hand, approaching a predator may be highly risky, particularly for individuals in small groups, creating an incentive to defect from joining the mob and free-ride on others' efforts 5,7,10. Under these circumstances, the identity of the initiator may provide crucial information to individuals deciding whether to join the mobbing group, thus influencing the magnitude of the group response. In many species, alarm vocalisations could provide an important cue to initiator identity. However, most research to date research has focused on alarm calls that elicit individual evasive behaviour rather than collective mobbing. If alarm calls signal an imminent and severe threat, failure to respond could be fatal, so individuals may benefit from responding with evasive action regardless of who produced the call. Meerkats (Suricata suricatta), for example, live under high predation pressure and, although their alarm calls are individually distinctive, their responses are unaffected by the identity of the caller 11. Caller characteristics may be more likely to influence alarm responses if the level of risk is relatively low, or particular categories of individuals are especially vulnerable. Yellow-bellied marmots, Marmota flaviventris, for example, respond more strongly to the alarm calls of vulnerable juveniles than those of adult females, but do not appear to discriminate between the calls of different individuals within the same age/sex category 12. Individual vocal discrimination could be advantageous if some callers are unreliable. Vervet monkeys (Chlorocebus pygerythrus), for instance, cease to respond the inter-group alarm calls of individuals that appear (through repeated playbacks of their calls) to "cry wolf ", calling there is no other group is present 13. Such selective responses are not apparent, however, in the higher-risk context of anti-predator alarm calls. Here, group members habituated to a particular individual's leopard-specific alarm calls nevertheless showed strong responses to that same individual's eagle-specific call 13. These results suggest that threat level plays an important role in determining the impact of individual caller identity on receivers' responses to alarms.
uu.diva-portal.org
Predation is a powerful agent of natural selection, driving the evolution of antipredator calls [1]. These calls have been shown to communicate predator category and/or predator distance to conspecifics . However, the risk posed by predators depends also on predator behavior , and the ability of prey to communicate predator behavior to conspecifics would be a selective advantage reducing their predation risk. I tested this idea in Siberian jays (Perisoreus infaustus), a group-living bird species. Predation by hawks, and to a lesser extent by owls, is substantial and the sole cause of mortality in adult jays . By using field data and predator-exposure experiments, I show here that jays used antipredator calls for hawks depending on predator behavior. A playback experiment demonstrated that these prey-to-prey calls were specific to hawk behavior (perch, prey search, attack) and elicited distinct, situation-specific escape responses. This is the first study to demonstrate that prey signals convey information about predator behavior to conspecifics. Given that antipredator calls in jays aim at protecting kin group members , consequently lowering their mortality [9], kin-selected benefits could be an important factor for the evolution of predator-behavior-specific antipredator calls in such systems.
Predation risk drives the expression of mobbing across bird species
Behavioral Ecology, 2017
Many species approach predators to harass and drive them away, even though mobbing a predator can be deadly. However, not all species display this behavior, and those that do can exhibit different behaviors while mobbing different predators. Here we experimentally assessed the role of social and ecological traits on the expression of mobbing behavior in a bird community in SE Brazil (n = 157 species). We exposed birds to models of two morphologically similar diurnal owls that pose different risks, and assessed which species engaged in mobbing. Among those that mobbed, we evaluated how they adjusted their mobbing behavior depending on the predator type. We tested the hypothesis that only species that are at risk and can afford to mob engage in this antipredator behavior. We found that species that engaged in mobbing are in the body mass range of potential prey, forage in the understory or in the canopy, and form flocks. A species' social system did not influence its mobbing behavior. Furthermore, species that engaged in mobbing formed larger mobbing assemblages when facing a high-risk predator, but mobbed more intensely when facing a low-risk predator. Our findings support our predictions, namely that the expression of mobbing is limited by its costs.
1 Caller characteristics influence recruitment to collective anti-predator events in 2 jackdaws 3
2018
Across the animal kingdom, examples abound of individuals coming together to repel 9 external threats. When such collective actions are initiated by recruitment signals, individuals 10 may benefit from being selective in whom they join, so the identity of the initiator may 11 determine the magnitude of the group response. However, the role of signaller discrimination 12 in coordinating group-level responses has yet to be tested. Here we show that in wild 13 jackdaws, a colonial corvid species, collective responses to anti-predator recruitment calls are 14 mediated by caller characteristics. In playbacks next to nestboxes, the calls of nestbox 15 residents attracted most recruits, followed in turn by other colony members, non-colony 16 members and rooks (a sympatric corvid). Playbacks in fields outside nestbox colonies, where 17 the immediate threat to broods was lower, showed similar results, with highest recruitment to 18 nearby colony members’ calls. Responses were further influen...
A songbird mimics different heterospecific alarm calls in response to different types of threat
Behavioral Ecology, 2014
Birds frequently mimic other species' alarm calls, but the type of information conveyed to receivers, and therefore the function of mimetic alarm calls, is often unknown. Alarm calls can convey predator-specific information that influences how receivers respond: aerial alarms signal the presence of flying predators and provoke receivers to flee, whereas mobbing alarm calls signal the presence of less dangerous predators and provoke receivers to mob. The function of mimetic alarm calls may therefore depend on the type of heterospecific alarm calls mimicked. We examined the use of alarm call mimicry by brown thornbills (Acanthiza pusilla) across different contexts of danger: terrestrial threat, aerial threat, when captured by a predator and during nest attack. Thornbills were most likely to include mimetic alarm calls among their vocalizations when captured and during nest attack, less likely in response to terrestrial and aerial predator threats, and least likely in the absence of any threat. Furthermore, the type of danger affected the type of mimetic alarm calls used: thornbills mimicked mobbing alarm calls in response to terrestrial threat and aerial alarm calls in response to aerial threat but also during capture and nest attack where no aerial danger was present. We suggest that mimicking predator-appropriate heterospecific alarm calls in response to aerial and terrestrial threats may facilitate interspecific alarm communication with other prey species, whereas mimicking heterospecific aerial alarm calls in the absence of aerial predators might deceptively startle predators to release captured callers or offspring when attacked.
Interspecific audience effects on the alarm-calling behaviour of a kleptoparasitic bird.
Audience effects are increasingly recognized as an important aspect of intraspecific communication. Yet despite the common occurrence of interspecific interactions and considerable evidence that individuals respond to the calls of heterospecifics, empirical evidence for interspecific audience effects on signalling behaviour is lacking. Here we present evidence of an interspecific audience effect on the alarm-calling behaviour of the kleptoparasitic fork-tailed drongo (Dicrurus adsimilis). When foraging solitarily, drongos regularly alarm at aerial predators, but rarely alarm at terrestrial predators. In contrast, when drongos are following terrestrially foraging pied babblers (Turdoides bicolor) for kleptoparasitic opportunities, they consistently give alarm calls to both aerial and terrestrial predators. This change occurs despite no difference in the amount of time that drongos spend foraging terrestrially. Babblers respond to drongo alarm calls by fleeing to cover, providing drongos with opportunities to steal babbler food items by occasionally giving false alarm calls. This provides an example of an interspecific audience effect on alarm-calling behaviour that may be explained by the benefits received from audience response.