False Alarm Calls Research Articles

Feeling anxious? The mechanisms of vocal deception in tufted capuchin monkeys

An ability to deceive conspecifics is thought to have favoured the evolution of large brains in social animals, but evidence that such behaviours require cognitive complexity is lacking. Tufted capuchin monkeys (Sapajus spp.) have been documented to use false alarm calls during feeding in a manner that functions to deceive competitors. However, comparative evidence suggests that the production of vocalizations by nonhuman primates is largely underpinned by emotional mechanisms, calling into question more cognitive interpretations of this behaviour. To determine whether emotional states are plausibly necessary and sufficient to proximately explain deceptive alarm call production, we examined the association between self-directed behaviours (SDBs), as a proxy for anxiety, and the production of spontaneous false alarm calls among tufted capuchins. Specifically, we predicted that if anxiety is necessary for the production of false alarms, then individuals that produce spontaneous false alarms should exhibit more SDBs in those contexts in which they call. If anxiety is also sufficient to explain the false alarm call production, then we predicted that individuals that call more in a given context would show higher rates of SDBs in that context, and that high rates of calling would be temporally associated with high rates of SDBs. Our results support the contention that states of anxiety are necessary for an individual to spontaneously produce false alarms, but that such states are not sufficient to explain patterns of calling. The link between anxiety and deceptive calling thus appears complex, and cognitively based decision-making processes may play some role in call production.

Using the vulnerable localities index to identify priority areas for targeting fire safety services

The Vulnerable Localities Index (VLI) is a popular analytical method used by police agencies in England and Wales to identify residential neighbourhoods that should be prioritised for attention. The VLI uses data on crime, deprivation and socio-demography to form a single composite index value for small geographic areas, which when mapped can assist in determining where to target neighbourhood policing and crime prevention initiatives. Its use has also helped to prompt other public sector partners such as local municipal government agencies to recognise the collaborative role that they could play with the police in helping to address mutual issues of public safety. Fire safety agencies have also expressed interest in the VLI, but to date this has mainly involved offering a supporting role to the police and local community safety partnerships on crime specific matters of public safety, with a focus on fire safety often on the periphery. In part this is due to limited analysis into whether the priority areas identified by the VLI are also areas of key concern to fire services. This research explores this relationship, identifying that the priority neighbourhoods of interest to the police are also areas where there are significantly higher than expected levels of deliberate fires and malicious false alarm calls to the fire service. These findings suggest that in the spirit of partnership working, potential opportunities exist in achieving mutually beneficial gains in improving public safety through the collaboration of fire, police and other local public service delivery.

Proximate Factors Underpinning Receiver Responses to Deceptive False Alarm Calls in Wild Tufted Capuchin Monkeys: Is It Counterdeception?

Previous research demonstrates that tufted capuchin monkeys use terrestrial predator alarm calls in a functionally deceptive manner to distract conspecifics when feeding on contestable resources, although the success of this tactic is limited because listeners frequently ignore these calls when given in such situations. While this decreased response rate is suggestive of a counterstrategy to deception by receivers, the proximate factors underpinning the behavior are unclear. The current study aims to test if the decreased response rate to alarm calls in competitive contexts is better explained by the perception of subtle acoustic differences between predator-elicited and deceptive false alarms, or by receivers varying their responses based on the context in which the signal is received. This was tested by first examining the acoustic structure of predator-elicited and deceptive false alarms for any potentially perceptible acoustic differences, and second by comparing the responses of capuchins to playbacks of each of predator-elicited and false alarms, played back in noncompetitive contexts. The results indicate that deceptive false alarms and predator-elicited alarms show, at best, minimal acoustic differences based on the structural features measured. Likewise, playbacks of deceptive false alarms elicited antipredator reactions at the same rate as did predator-elicited alarms, although there was a nonsignificant tendency for false alarms to be more likely to elicit escape reactions. The lack of robust acoustic differences together with the high response rate to false alarms in noncompetitive contexts suggests that the context in which the signal is received best explains receiver responses. It remains unclear, however, if listeners ascribe different meanings to the calls based on context, or if they generally ignore all signals in competitive contexts. Whether or not the decreased response rate of receivers directly stems from the deceptive use of the calls cannot be determined until these latter possibilities are rigorously tested. Am. J. Primatol. 75:715-725, 2013. © 2012 Wiley Periodicals, Inc.

Investigating a link between bill morphology, foraging ecology and kleptoparasitic behaviour in the fork-tailed drongo

Fork-tailed drongos, Dicrurus adsimilis , are facultative kleptoparasites of many bird and mammal species. They use complex alarm call strategies, a combination of both true and false alarm calls, to procure food items from their hosts. The evolution of this interspecific interaction may have been catalysed by a selective benefit for drongos that were able to procure a wider diversity of food resources through kleptoparasitism . We tested the hypothesis that drongos, which principally hawk their prey from a perch, employ kleptoparasitism to exploit a terrestrial foraging niche for which they do not possess the appropriate morphological adaptations, as indicated by bill morphology. We analysed the bill characteristics of the terrestrially foraging pied babbler, Turdoides bicolor , a primary host for the fork-tailed drongo, and both drongo and pied babbler museum specimens to establish potential links between differences in functional morphology and foraging ecology. We also observed the foraging behaviour of babblers and drongos in the Kalahari Desert . Drongo bills were significantly shorter, thicker and less curved than those of pied babblers, and large energy-rich subterranean prey items, such as insect larvae , were not procured by drongos while self-foraging. Furthermore, drongos preferentially attempted to kleptoparasitize prey types that they did not capture while self-foraging. We suggest that the calorific and nutrient content of a larger and more diverse set of prey, particularly buried larvae, which drongos did not excavate on their own, establishes a selection pressure for kleptoparasitism and may have contributed to the complex behavioural interactions between drongos and their hosts. ► Fork-tailed drongos kleptoparasitize pied babblers. ► We analyse bill morphology and foraging differences between drongos and babblers. ► Drongos target excavated prey when kleptoparasitizing babblers. ► Drongos possess significantly shorter, thicker bills than babblers. ► Procuring subterranean prey may partially incentivize kleptoparasitic behaviour.

Kleptoparasitism by attacks versus false alarm calls in fork-tailed drongos

Many animals steal food, termed kleptoparasitism, but attacks are frequently unsuccessful and may incur costs. Some species produce false alarm calls during kleptoparasitism, but the relative benefits of this versus physical attacks are not known. We investigated the kleptoparasitic behaviour of a population of individually recognizable and habituated fork-tailed drongos, Dicrurus adsimilis, which kleptoparasitize food using both false alarms and physical attacks. Drongos made false alarms more frequently when kleptoparasitizing small food items, probably because these can be more profitably stolen by false alarm than attack. False alarms were also more frequent when targets were larger species, which are likely to be more costly to attack since they more frequently defended food. Drongos were able to attack targets when a false alarm had failed but rarely did so, even though such attacks were no less successful than attacks when no false alarm had been made. It therefore appears that false alarms increase opportunities for kleptoparasitism because calls can be made when attacks are unprofitable. False alarm calls also appear to benefit drongos by increasing overall success in kleptoparasitism, because attacks could be made following failed false alarm calls. This is the first study to show the functional benefits of making false alarm calls, illustrating how they may be deployed strategically in kleptoparasitism when attacks would be less profitable or even unprofitable. More generally, false alarms may evolve where animals engage in physical conflict over resources because they can benefit individuals by decreasing the costs of competition.

Fork-tailed drongos use deceptive mimicked alarm calls to steal food

Despite the prevalence of vocal mimicry in animals, few functions for this behaviour have been shown. I propose a novel hypothesis that false mimicked alarm calls could be used deceptively to scare other species and steal their food. Studies have previously suggested that animals use their own species-specific alarm calls to steal food. However none have shown conclusively that these false alarms are deceptive, or that mimicked alarm calls are used in this manner. Here, I show that wild fork-tailed drongos (Dicrurus adsimilis) make both drongo-specific and mimicked false alarm calls when watching target species handling food, in response to which targets flee to cover abandoning their food. The drongo-specific and mimicked calls made in false alarms were structurally indistinguishable from calls made during true alarms at predators by drongos and other species. Furthermore, I demonstrate by playback experiments that two of these species, meerkats (Suricata suricatta) and pied babblers (Turdoides bicolor), are deceived by both drongo-specific and mimicked false alarm calls. These results provide the first conclusive evidence that false alarm calls are deceptive and demonstrate a novel function for vocal mimicry. This work also provides valuable insight into the benefits of deploying variable mimetic signals in deceptive communication.

Assessing “false” alarm calls by a drongo (Dicrurus paradiseus) in mixed-species bird flocks

The suggestion that some members of mixed-species bird flocks use alarm calls when predators are not present in order to startle other species and thereby gain access to additional prey, first postulated by Munn (Munn CA. 1986. Birds that ‘cry wolf’. Nature. 391:143–145.), has generated considerable interest due to its implication that the calling birds are intentionally deceiving listeners. Despite this interest, ‘‘false alarms’’ have been studied rarely and without detailed acoustical analysis. We explored whether false alarms are used by Greater Racket-tailed Drongos, which produce a distinctive set of notes when alarmed. We found that drongos did indeed make false alarms, defined as an alarm vocalization made either while the bird was on the perch or in the air, and followed within 10 s by a foraging attempt. However, the acoustic features of the call notes used, particularly of those calls made in the air, were more similar to aggressive calls, made when drongos chased each other, than to actual alarms produced when predators were present. Drongo foraging success was greater after false alarm calls than after silence or nonalarm vocalizations, and playback of false alarms in the air induced escape behavior in other species, though at a lower level than actual alarms. Thus, although drongos can use false alarms to startle other birds and gain foraging opportunities, such calls cannot be called ‘‘false’’ with certainty because they may also signal aggressive intent. Indeed, aggression and alarm may be intertwined in this family of birds as drongos actively mob or chase many predators, including bird-eating hawks. Key words: aggressive interactions, alarm calls, deception, Dicrurus paradiseus, false alarms, interspecific communication, mixed-species flocks. [Behav Ecol]

Specific targeting of host individuals by a kleptoparasitic bird

Kleptoparasitism is a tactic used to acquire food opportunistically and has been shown to provide several benefits, including greater food intake rate and the acquisition of items not normally available during self-foraging. Host individuals may differ in their ability to defend themselves against kleptoparasitic attacks and therefore identifying those host individuals that are particularly vulnerable to attack could both provide energetic benefits and increase the efficiency of kleptoparasitism as a foraging strategy. Here, we show that the kleptoparasitic fork-tailed drongo (Dicrurus adsimilis) specifically targets juveniles when following groups of cooperatively breeding pied babblers (Turdoides bicolor). Drongos give alarm calls upon sighting a predator, thus providing extra predator vigilance to foraging pied babblers. However, drongos also use alarm calls to steal food items. During kleptoparasitic attacks, drongos give false alarm calls and then swoop down to steal food items dropped by alarmed babblers. Juvenile pied babblers are particularly vulnerable to attack because they (a) spend a longer period handling prey items prior to consumption and (b) respond to alarm calls primarily by immediately moving to cover, in contrast to adults who respond by looking up and visually scanning the surrounding area. Drongos attack juvenile babblers significantly more often than adults, with attacks on juveniles more likely to result in the successful procurement of a food item. This patterns of attack suggests that drongos are able to differentiate between individuals of different age when targeting pied babblers, thus increasing the efficiency of kleptoparasitism as a foraging strategy.

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.

Facultative response to a kleptoparasite by the cooperatively breeding pied babbler

In many cases of interspecific kleptoparasitism, hosts develop defensive behaviors to minimize the impact of kleptoparasites. Because vigilance and defensive behaviors are often costly, selection should favor hosts that adjust the amount of investment needed to minimize losses to kleptoparasitism. However, examples of such facultative responses are rare. Here, we investigate the response of cooperatively breeding pied babblers (Turdoides bicolor) to the drongo (Dicrurus adsimilis), an avian kleptoparasite that regularly follows pied babbler groups, often giving alarm calls to alert the group to predators but also occasionally giving false alarm calls in order to steal food items. We show that pied babbler response to drongos varies markedly according to babbler group size. In small groups, where there are few individuals available to act as sentinels, babblers sentinel less when a drongo is present and respond strongly to drongo alarm calls. However, in large groups, where there are many individuals available to participate in predator vigilance, babblers sentinel more often when a drongo is present, rarely respond to drongo alarm calls, and aggressively displace drongos, with a consequent decline in the number of successful kleptoparasitism events. This behavior represent a facultative response to a kleptoparasite according to the costs versus benefits of tolerating their presence.

Reducing False Security Alarm Calls for Police Service: A Policy Research Note

False alarm calls are a substantial resource allocation problem for police administrators even though the issue tends not to be high profile. A panel design is utilized to describe how one municipal fine schedule affects the generation of false security alarm calls for police service by residential, commercial, and nonprofit property types. It was found that property type accounts for12% of the variation in annual false alarm generation and that, on average, false alarm production decreased substantially over time.

The Role of Alarms and CCTV in Detecting Non-residential Burglary

This study is concerned with the role of burglar alarms and CCTV in the detection of non-residential burglary. Funded by the UK Home Office's Policing and Reducing Crime Unit, it involves surveys of police officers, supplemented by police data, site surveys and victim interviews. Alarms and CCTV made important contributions to detecting burglaries, in terms of on-scene capture and arrests due to using eye-witness descriptions and filmed recordings for identifying offenders. There may be potential to increase numbers of detected cases by fitting more of both security devices, but this partly depends on patrol workloads, filtering out the bulk of false alarm calls and minimising the tendency for activated, audible alarms to reduce CCTV suspect recordings by prompting the burglar's flight. This might be best resolved either by fitting delayed-audible alarms or alarms that do not trigger on entry to premises, though this might result in goods being taken at more incidents, or by installing a combination of CCTV cameras on the outside of premises with alarms at entry points. Hidden CCTV also appears to be better than visible cameras for filming and identifying suspects. Implications of findings for research design are also considered.

False Alarm Calls as a Means of Resource Usurpation in the Great Tit Parus major

AbstractGreat tits Parus major regularly gave alarm calls in winter without the presence of actual or potential predators. Such false alarm calls were given to deceive both conspecifics and heterospecifics. False calls were given when flock‐feeding sparrows Passer spp. monopolized a concentrated food source; if the food resource was dispersed false alarm calls were not used, independently of the presence of sparrows. Dominant great tits used alarm calls deceptively if a dominant conspecific was present on a concentrated food source but not if a subdominant individual was present; subdominant great tits were displaced by means of threat displays. Subdominant individuals gave false alarm calls both if dominant or subdominant conspecifics were present. False alarm calls were especially used when food was scarce or when great tits were feeding at a high rate, i.e. during snow storms and in the morning and the afternoon.

Some ergonomic and other aspects of the causes of false alarm calls from intruder alarm systems : Bozeat, N.et al In: Proceedings of 6th Congress of the International Ergonomics Association “Old World, New World, One World” and Technical Programme of the 20th Annual Meeting of the Human Factors Society. Jul 1976, pp 479–483

Some ergonomic and other aspects of the causes of false alarm calls from intruder alarm systems : Bozeat, N.et al In: Proceedings of 6th Congress of the International Ergonomics Association “Old World, New World, One World” and Technical Programme of the 20th Annual Meeting of the Human Factors Society. Jul 1976, pp 479–483

Some Ergonomic and Other Aspects of the Causes of False Alarm Calls from Intruder Alarm Systems

The paper summarises a report concerning a diagnostic study of false alarm causation in the city of Birmingham, England. The study involved an analysis of Police computer records, alarm company files, data from public services, and a survey of 100 false alarms in a city police division. The study was occasioned by the fact that in the United Kingdom approximately 98% of alarm calls are false, costing 106 man-hours per annum in Police response, and the growth of the industry indicates that the latter figure will increase by 15% per annum. Major findings are that between 50% and 75% of false alarms are attributable to ‘human error’ in design, installation, and operation of the system, and that 70% of these seem to be due to the repetition of the immediately previous cause. Recommendations are discussed, involving in the main additional human factors training, and better liaison between the various parties in the security industry.