High Calling Rates Research Articles

Group vocal composition and decision-making during roost finding in Spix's disk-winged bats.

Theoretical work suggests that having many informed individuals within social groups can promote efficient resource location. However, it may also give rise to group fragmentation if members fail to reach consensus on their direction of movement. In this study, we investigate whether the number of informed individuals, exemplified by bats emitting calls from different roosts, influences group cohesion in Spix's disk-winged bats (Thyroptera tricolor). Additionally, we explore the role of signal reliability, quantified through signalling rates, in group consensus on where to roost. These bats use contact calls to announce the location of a roost site and recruit conspecifics. The groups they form exhibit high levels of cohesion and consist of both vocal and non-vocal bats, with vocal behaviour being consistent over time. Our findings revealed that an increase in the number of roosts broadcasting calls is strongly associated with the likelihood of groups fragmenting among multiple roosts. Additionally, we found that a majority of group members enter the roost with higher calling rates. This phenomenon can mitigate the risk of group fragmentation, as bats emitting more calls may contribute to greater group consensus on roosting locations, thereby reducing the likelihood of individuals separating and enhancing overall group cohesion. Our results highlight the potential costs of having too many information producers for group coordination, despite their established role in finding critical resources. This article is part of the theme issue 'The power of sound: unravelling how acoustic communication shapes group dynamics'.

Vocal rhythms in nesting Lusitanian toadfish, Halobatrachus didactylus

Males of several fish species aggregate and vocalize together, increasing the detection range of the sounds and their chances of mating. In the Lusitanian toadfish (Halobatrachus didactylus), breeding males build nests under rocks in close proximity and produce hundreds of boatwhistles (BW) an hour to attract females to lay their demersal eggs on their nests. Chorusing behaviour includes fine-scale interactions between individuals, a behavioural dynamic worth investigating in this highly vocal fish. Here we present a study to further investigate this species' vocal temporal patterns on a fine (individual rhythms and male-male interactions) and large (chorus daily patterns) scales. Several datasets recorded in the Tagus estuary were labelled with the support of an automatic recognition system based on hidden Markov models. Fine-scale vocal temporal patterns exhibit high variability between and within individuals, varying from an almost isochronous to an apparent aperiodic pattern. When in a chorus, males exhibited alternation or synchrony calling patterns, possibly depending on motivation and social context (mating or male-male competition). When engaged in sustained calling, males usually alternated vocalizations with their close neighbours thus avoiding superposition of calls. Synchrony was observed mostly in fish with lower mean calling rate. Interaction patterns were less obvious in more distanced males. Daily choruses showed periods with several active calling males and periods of low activity with no significant diel patterns in shallower intertidal waters. Here, chorusing activity was mainly affected by tide level. In contrast, at a deeper location, although tidal currents causes a decrease in calling rate, tide level did not significantly influence calling, and there was a higher calling rate at night. These data show that photoperiod and tide levels can influence broad patterns of Lusitanian toadfish calling activity as in other shallow-water fishes, but fine temporal patterns in acoustic interactions among nesting males is more complex than previously known for fishes.

Effects of corticosterone treatment and wound healing on reproductive traits of American bullfrogs.

During reproductive season, calling anuran males display high testosterone (T) and episodically high corticosterone (CORT) plasma levels, which are positively associated with higher calling rates and immunocompetence. However, exposure to constant stress stimuli can result in chronically elevated CORT levels, possibly leading to inhibition of reproductive and immune activity. Reproduction and immune responses are energetically expensive, so when an animal is immunologically challenged, a tradeoff might be expressed, with CORT potentially mediating it. Our aim was to test how episodic and chronic CORT treatments, alongside wound healing, would affect reproduction in American bullfrog males (Lithobates catesbeianus). Forty animals were divided in four groups: Episodic CORT (daily transdermic application of CORT), placebo (daily transdermic application of sesame oil), chronic CORT (subcutaneous CORT silastic implants), and sham control (subcutaneous empty silastic implants). One week after treatments began, animals were punctured in the leg with a biopsy needle and the wound was photographed after 45 days to determine wound healing status (WS). Blood samples were collected throughout the experiment to measure CORT and T plasma levels. After animal euthanasia, testes were dissected, fixed, and analyzed histologically to determine spermatogenic activity (germinative cyst [GmC] morphometrics). As expected, the episodic CORT treatment had no effect on T plasma levels or spermatogenic activity. On the other hand, chronic CORT treatment reduced GmC morphometric traits, indicating suppression of reproduction, although T levels were not altered. In addition, animals from sham control and chronic CORT treatments with higher T levels presented higher WS, which indicates an immune-enhancing T effect.

Interpersonal brain synchronization under bluffing in strategic games.

People commonly use bluffing as a strategy to manipulate other people’s beliefs about them for gain. Although bluffing is an important part of successful strategic thinking, the inter-brain mechanisms underlying bluffing remain unclear. Here, we employed a functional near-infrared spectroscopy hyperscanning technique to simultaneously record the brain activity in the right temporal-parietal junction in 32 pairs of participants when they played a bluffing game against each other or with computer opponents separately. We also manipulated the penalty for bluffing (high vs low). Under the condition of high relative to low penalty, results showed a higher bluffing rate and a higher calling rate in human-to-human as compared to human-to-computer pairing. At the neural level, high relative to low penalty condition increased the interpersonal brain synchronization (IBS) in the right angular gyrus (rAG) during human-to-human as compared to human-to-computer interaction. Importantly, bluffing relative to non-bluffing, under the high penalty and human-to-human condition, resulted in an increase in response time and enhanced IBS in the rAG. Participants who bluffed more frequently also elicited stronger IBS. Our findings support the view that regions associated with mentalizing become synchronized during bluffing games, especially under the high penalty and human-to-human condition.

Pre-maturation social experience affects female reproductive strategies and offspring quality in a highly polyandrous insect

Pre-maturation social experiences may affect post-maturation reproductive strategies of females, including mating preferences and investment in offspring. Whether pre-maturation social experiences affect other aspects of females’ reproductive strategies, including the number of accepted males and post-copulatory decisions, is still an open question. To address this question, we performed laboratory experiments using the highly polyandrous cricket Teleogryllus commodus. Previous studies showed that juvenile females reared in an acoustic environment with male calls of different rates (MIX) are more responsive to highly attractive calls than females reared in an environment with male calls of only high calling rates (HIGH). We exposed juvenile females to the same two acoustic environments (MIX and HIGH) and estimated the number of accepted males, time of spermatophore retention, and offspring quality. We found that the acoustic environment did not change the number of accepted males, indicating that the higher responsiveness shown in a previous study does not translate into high degree of polyandry. An increased number of mates reduced offspring quality, suggesting that polyandry is costly to females. Finally, when compared with females of the HIGH group, females of the MIX group retained spermatophores for shorter periods and produced higher quality offspring if mated with highly attractive males. This finding suggests that both the pre-maturation acoustic environment and the quality of the mates found by the adult females determine their post-copulatory decisions and eventually offspring quality. Taken together, our results indicate that both the pre- and post-mating strategies of females are subject to socially cued plasticity. There is increasing evidence that pre-maturation experiences affect mating decisions of females after maturity, making them more or less selective. Both the pre-maturation social environment and the quality of potential mates found by an adult female may determine the number and quality of accepted males, which in turn may influence offspring quality. We experimentally tested this hypothesis using a highly polyandrous cricket species and showed that the pre-maturation acoustic environment does not affect the number and attractiveness of males accepted by the females. However, offspring quality was determined by an interaction between the pre-maturation acoustic environment and attractiveness of males accepted by the females. This result provides a link between the pre- and post-maturation social experience of a female and the quality of her offspring.

Monitoring the annual vocal activity of two enigmatic nocturnal Neotropical birds: the Common Potoo (Nyctibius griseus) and the Great Potoo (Nyctibius grandis)

Potoos (Nyctibius spp.) are nocturnal Neotropical canopy-dwelling birds, making them one of the most enigmatic and least known avian families. The Common Potoo (Nyctibius griseus) and the Great Potoo (Nyctibius grandis) are the most widespread species, but little information on their life histories is available. We evaluated the utility of autonomous recording units, coupled with automated signal recognition software, to monitor the calling behavior of both species for the first time over a complete annual cycle at six different sites in the Brazilian Pantanal. Their diel activity was restricted to the night, with higher calling rates after midnight. The breeding season of the Common Potoo, according to seasonal changes in vocal activity, seems to occur between July and November, while the breeding period of the Great Potoo extended from July to December. The reproduction periods proposed for each potoo in this study correspond mainly with the dry season in the study area and are in agreement with the few historical nest site observations from Brazil. The maximum calling activity of both species occurred between 1 and 5 a.m. September was the month with the maximum vocal activity of the Common Potoo, while the Great Potoo was most vocally during October. The vocal activity of neither potoo was related to night temperature. The Great Potoo was more vocally active during nights with high moon illumination. Our results will be useful in future monitoring programs for these species. Acoustic monitoring has proven to be a helpful tool for monitoring the presence and calling seasonality of the Common Potoo and the Great Potoo, mainly due to their naturally low vocal activity rates. Acoustic monitoring should be evaluated and used to increase our knowledge about the ethology and ecology of this enigmatic avian family.

Effect of tobacco control policies on the Swedish smoking quitline using intervention time-series analysis

ObjectivesTo coherently examine the responsiveness of the Swedish National Tobacco Quitline (SNTQ) to different types of anti-smoking policies over an extended period of calendar time.DesignQuasi-experimental design with an intervention time-series...

Increasing the Number of Medical Emergency Calls Does Not Improve Hospital Mortality.

Medical emergency teams were established to rescue patients experiencing clinical deterioration thus preventing cardiac arrest and unexpected hospital mortality. Although hospitals are encouraged to increase emergency calling rates to improve in-hospital mortality, there are increasing concerns about the impact these calls have on the workload of the teams and the skill levels on the general wards. We set out to examine the relationship between emergency calling rates and adjusted in-hospital mortality. Retrospective analysis of prospectively collected patient and emergency call data. Tertiary, metropolitan, and regional hospitals in the State of Victoria, Australia. Consecutive patients discharged from 1) St Vincent's Hospital Melbourne from January 2008 to June 2016 and 2) 15 Victorian hospitals from July 2010 to June 2015. We studied 441,029 patients from St Vincent's Hospital Melbourne. Median age was 61.0 years (interquartile range, 45-74 yr), 57.2% were men, and 0.70% died; monthly emergency calling rates varied between 9.21 and 30.69 (median 18.4) per 1,000 discharges. In-hospital mortality adjusted for age, gender, emergency status, same day admission, year of discharge, and Charlson Comorbidity Index was not reduced by higher calling rates in the month of discharge (odds ratio, 1.019; 95% CI, 1.008-1.031). We then examined 3,339,789 discharges from 15 Victorian hospitals with median age 61 years (interquartile range, 43-74 yr), 51.4% men, and hospital mortality 0.83% where yearly emergency calling rates varied from 18.46 to 33.40 (median, 25.75) per 1,000 discharges. Again, adjusted mortality was not reduced by higher calling rates in the year of discharge (odds ratio, 1.003; 95% CI, 1.001-1.006). With adjustment for patient factors, illness, and comorbidities, increased emergency calling rates were not associated with reduced in-hospital mortality. Efforts to increase calling rates do not seem warranted.

Siberian crane chick calls reflect their thermal state

Chicks can convey information about their needs with calls. But it is still unknown if there are any universal need indicators in chick vocalizations. Previous studies have shown that in some species vocal activity and/or temporal-frequency variables of calls are related to the chick state, whereas other studies did not confirm it. Here, we tested experimentally whether vocal activity and temporal-frequency variables of calls change with cooling. We studied 10 human-raised Siberian crane (Grus leucogeranus) chicks at 3–15 days of age. We found that the cooled chicks produced calls higher in fundamental frequency and power variables, longer in duration and at a higher calling rate than in the control chicks. However, we did not find significant changes in level of entropy and occurrence of non-linear phenomena in chick calls recorded during the experimental cooling. We suggest that the level of vocal activity is a universal indicator of need for warmth in precocial and semi-precocial birds (e.g. cranes), but not in altricial ones. We also assume that coding of needs via temporal-frequency variables of calls is typical in species whose adults could not confuse their chicks with other chicks. Siberian cranes stay on separate territories during their breeding season, so parents do not need to check individuality of their offspring in the home area. In this case, all call characteristics are available for other purposes and serve to communicate chicks’ vital needs.

Finely tuned choruses: bush crickets adjust attention to neighboring singers in relation to the acoustic environment they create

When acoustically advertising animals call in dense clusters, problems in signal efficacy often arise. These problems are particularly acute in species where females ignore males who call immediately following a neighbor and males adjust call timing to avoid broadcasting following calls: Males may forego such adjustments and produce many ineffective calls, they may attend to all neighbors and call at a reduced rate, or they may selectively attend to certain neighbors, likely those who are nearby and/or more intense. We studied the problem of group calling in Ephippiger diurnus, a European bush cricket distributed in genetically isolated populations that vary considerably in male song and chorusing and in female preference for male song. Female E. diurnus ignore following male calls, and males adjust their call timing but only with respect to several loud neighbors. We found that males were more selective in attending to only their nearest neighbor in a population where chorusing yields sound during a high proportion of a collective singing bout, and more indiscriminate in attending to several neighbors where chorusing yields more intermittent sound. Such fine tuning can maintain a relatively high calling rate and may be generated by positive feedback loops operating between individual and group-level calling traits. When animals sing in the company of conspecifics, individual singers often adjust their call timing such that they do not immediately follow neighbors. These adjustments become problematic in dense choruses, as adjusting for all neighbors could lead to a marked reduction in call rate. Consequently, some degree of selective attention, most likely to nearby and/or loud neighbors, is expected. We confirmed this expectation in the chorusing bush cricket E. diurnus, but we also found that the degree of attention varied among populations. In particular, singers were most selective, attending to only a single neighbor, where chorusing generated rather continuous sound and more indiscriminate attention would have led to sporadic calling. Thus, choruses appear to be finely tuned and controlled by feedback loops in which individual singers generate a collective display that, in turn, influences the singing behavior of those very same individuals.

Ultrasonic vocalizations in golden hamsters (Mesocricetus auratus) reveal modest sex differences and nonlinear signals of sexual motivation.

Vocal signaling is one of many behaviors that animals perform during social interactions. Vocalizations produced by both sexes before mating can communicate sex, identity and condition of the caller. Adult golden hamsters produce ultrasonic vocalizations (USV) after intersexual contact. To determine whether these vocalizations are sexually dimorphic, we analyzed the vocal repertoire for sex differences in: 1) calling rates, 2) composition (structural complexity, call types and nonlinear phenomena) and 3) acoustic structure. In addition, we examined it for individual variation in the calls. The vocal repertoire was mainly composed of 1-note simple calls and at least half of them presented some degree of deterministic chaos. The prevalence of this nonlinear phenomenon was confirmed by low values of harmonic-to-noise ratio for most calls. We found modest sexual differences between repertoires. Males were more likely than females to produce tonal and less chaotic calls, as well as call types with frequency jumps. Multivariate analysis of the acoustic features of 1-note simple calls revealed significant sex differences in the second axis represented mostly by entropy and bandwidth parameters. Male calls showed lower entropy and inter-quartile bandwidth than female calls. Because the variation of acoustic structure within individuals was higher than among individuals, USV could not be reliably assigned to the correct individual. Interestingly, however, this high variability, augmented by the prevalence of chaos and frequency jumps, could be the result of increased vocal effort. Hamsters motivated to produce high calling rates also produced longer calls of broader bandwidth. Thus, the sex differences found could be the result of different sex preferences but also of a sex difference in calling motivation or condition. We suggest that variable and complex USV may have been selected to increase responsiveness of a potential mate by communicating sexual arousal and preventing habituation to the caller.

Hybrid Scheme with Adaptive Replication and Mobility Anchoring Point (MAP) in Wireless Networks

Replication strategy is mostly useful for replicating the mobile user's profile at selected locations from which some callers have higher calling rate. Location management scheme also include replication strategy to reduce the location lookup cost of called mobile user. It plays important role in personal communication services in order to reduce call setup cost, call setup time, and increases the QoS (quality of service). In prior replication schemes, called user's location profile is placed at some fixed and limited number of visitor location registers (VLRs) based on call history of the caller. In prior hybrid schemes location update and replication strategies are combined together. These prior hybrid schemes apply pointer forwarding strategy and replication. But these schemes have limitations like holding "loose" form of location profile and higher location update cost. We have proposed a new hybrid scheme which includes adaptive replication of updated user's location profile and mobility anchoring point (MAP) for location update. The main objective of the proposed scheme is to reduce call setup cost and call setup time. In order to achieve the objective, adaptive replication is applied at certain visitor location registers (VLRs) according to movement of caller. The replica is kept updated at MAP and replicated to neighbor VLRs as per movement of the caller. We have presented fluid-flow based analytical modeling which shows that proposed scheme outperforms the prior hybrid scheme.

Chorusing Behaviour in the Lusitanian Toadfish: Should I Match My Neighbours' Calling Rate?

AbstractChoruses have been described mostly in birds, anurans and insects but have been poorly studied in fish. Research in batrachoidid (toadfishes) species suggest vocal facilitation among neighbouring males, but whether chorusing fish present more complex interactions is unknown. In this study, we test the hypothesis that chorusing fish males compete actively to increase attractiveness to females. We first describe vocal interactions in natural choruses of Lusitanian toadfish males. Our analysis found positive correlations between the calling rates of neighbouring males in several occasions. However, we also found that males that showed an overall low vocal activity throughout the observation period exhibited peaks of increased calling activity when neighbours decreased their calling rate, suggesting an opportunistic maximisation of attractiveness. We further test with playback experiments how toadfish males adjust calling activity relative to their neighbours'. We observed that males silent at the time of the playbacks but who had an overall high vocal performance tended to start calling when exposed to playbacks in contrast to low‐activity males. Playback experiments further showed that males initially calling at a high rate adjust their calling rate according to the neighbour's vocal activity level, that is, they increased calling rate when exposed to a high calling rate and decreased it when confronted with a low calling rate. However, males calling at a low rate did not significantly alter their calling rate when presented with a low (similar) or higher calling rate, probably due to temporary physiological and/or ecological constraints. We argue that Lusitanian toadfish males tend to optimise calling effort in relation to their neighbours when they are actively advertising. Further studies are necessary to better understand vocal behaviour with increased chorus size.

User's Profile Replication Tree and On Demand Replica Update in Wireless Communication

Replication strategy is mostly useful for replicating the called mobile user's profile at selected locations where some caller mobile users have higher calling rate. It plays important role in personal communication services (PCS) in order to reduce call setup cost and call setup time. In prior replication schemes, replicated sites (visitor location registers) have no inter relationship. We have proposed a novel and innovative replication tree which is buildup from replicated VLRs (visitor location registers). VLRs are replicated based on effective replication probability of caller mobile user. Home location register (HLR) keeps update replica at root VLR in the replication tree and root VLR forwards update replica to a VLR in the replication tree on demand. The main objective of the proposed scheme is to reduce call setup time and call setup cost by enabling replication of called mobile user's location profile at certain visitor location registers (VLRs) where caller mobile user roams. We have presented analytical modeling which shows that setting inter-relationship among the replicated sites helps in further reducing the call setup cost.

Counting addressing method: Command addressable element and extinguishing module

The specific requirements that appear in addressable fire detection and alarm systems and the shortcomings of the existing addressing methods were discussed. A new method of addressing of detectors was proposed. The basic principles of addressing and responding of a called element are stated. Extinguishing module is specific subsystem in classic fire detection and alarm systems. Appearing of addressable fire detection and alarm systems didn't caused essential change in the concept of extinguishing module because of long calling period of such systems. Addressable fire security system based on counting addressing method reaches high calling rates and enables integrating of the extinguishing module in addressable system. Solutions for command addressable element and integrated extinguishing module are given in this paper. The counting addressing method was developed for specific requirements in fire detection and alarm systems, yet its speed and reliability justifies its use in the acquisition of data on slowly variable parameters under industrial conditions.

Variation in Call Structure and Calling Behavior in Treefrogs of the Genus Scinax

Abstract We investigated calling behavior and call structure for eight species of treefrogs in the genus Scinax, and document noteworthy patterns of interspecific variation that largely reflect habitat and social environment in this report. The five species in the S. ruber clade call in open areas or forest edges near standing water and produce simple calls at relatively high rates and low to moderate frequencies. Species from the S. catharinae clade call from more forested habitats and produce complex, higher frequency calls at relatively low rates. Differences in the range of activity temperatures and habitats among species reflect differences in geographical distribution and spatio-temporal selection of microhabitat during calling. In general, species with high calling rates also had high rates of locomotion during calling activity and were active at warmer temperatures. One exception was S. crospedospilus, which has an extremely high calling rate but exhibits among the lowest rates of locomotion and a...

Sex-specific responses to vocal convergence and divergence of contact calls in orange-fronted conures (Aratinga canicularis)

We investigated the signal function of vocal imitation of contact calls in orange-fronted conures (OFCs; Aratinga canicularis) in Costa Rica. OFCs live in dynamic social systems with frequent flock fusions and fissions. Exchanges of contact calls precede these flock changes. During call exchanges, the similarity between the contact calls of different individuals may either increase (converge) or decrease (diverge). We conducted a playback experiment on wild-caught captive birds in which we simulated convergent, divergent and no-change interaction series with male and female contact calls. OFCs responded differently to convergent and divergent series of contact calls, but only when we considered the sex of the test birds. Males called most in response to convergent series, whereas females demonstrated high calling rates in response to both convergent and divergent interactions. Both sexes responded most to contact calls from the opposite sex, but overall females produced more calls and had shorter latencies to calling than males. These results demonstrate that OFCs can discriminate between male and female contact calls and that subtle changes in contact call structure during interactions have signal function. The stronger overall response to convergent series suggests that convergence of contact calls is an affiliative signal.

Analyzing acoustic interactions in natural bullfrog (Rana catesbeiana) choruses.

Analysis of acoustic interactions between animals in active choruses is complex because of the large numbers of individuals present, their high calling rates, and the considerable numbers of vocalizations that either overlap or show close temporal alternation. The authors describe a methodology for recording chorus activity in bullfrogs (Rana catesbeiana) using multiple, closely spaced acoustic sensors that provide simultaneous estimates of sound direction and sound characteristics. This method provides estimates of location of individual callers, even under conditions of call overlap. This is a useful technique for understanding the complexity of the acoustic scene faced by animals vocalizing in groups.

CALLING IS AN HONEST INDICATOR OF PATERNAL GENETIC QUALITY IN POISON FROGS

Several competing hypotheses have been put forward to explain why females of many species mate preferentially with males possessing the most conspicuous signals (e.g., ornaments, displays, or songs). We performed a laboratory experiment using two species of poison frogs, Dendrobates leucomelas and Epipedobates tricolor, to test the hypothesis that male calling performance is an honest indicator of parental quality. Our analyses are based on data from behavioral observations of mating activities of captive-reared individuals (and their offspring) that were housed in terraria for four consecutive breeding seasons. Male mating success increased with male calling rate and chirp duration in both species, suggesting that females preferred males with more elaborate calls. Because calling performance improved with age in D. leucomelas, female poison frogs that prefer males with more elaborate calls in the wild may end up mating with older males that have already proven their ability to survive. Females that mated with good callers obtained higher quality offspring. Eggs fertilized by males with high calling rates and long chirp durations had higher hatching success and produced tadpoles that were more likely to metamorphose into surviving frogs. As a consequence, females that mated with males with high calling performance obtained more surviving offspring per egg, compared to females that mated with poor callers. Collectively, our findings comply with the notion that female poison frogs prefer to mate with good callers because calling performance is a reliable predictor of offspring quality. The possible influence of maternal allocation and reasons for the strong effect size compared to previous studies are discussed.

Interspecific responses to distress calls in bats (Chiroptera: Vespertilionidae): a function for convergence in call design?

Distress calls were recorded from three sympatric species of pipistrelle bat (Pipistrellus nathusii, P. pipistrellus and P. pygmaeus) in England and Northern Ireland. At foraging sites, we conducted playback experiments, consisting of experimental distress call sequences from each species and control sequences of random noise and sound recorded with no bats present. We measured response by simultaneously recording ultrasound during playbacks and counting the echolocation pulses above a predetermined threshold which were then identified to species. All three species responded to each other's calls. The number of recorded echolocation pulses of all species increased eight-fold, on average, during the playback of distress call sequences compared with the playback of ultrasonic noise, and four-fold compared with the playback of silence. In a separate playback experiment, the number of echolocation pulses of P. pygmaeus increased 14-fold during the playback of distress calls of four endemic species of bat from Madagascar (Emballonura atrata, Myotis goudoti, Miniopterus majori and M. manavi) compared with the playback of silence. This increased response might have been caused by the high calling rates of the Malagasy species. Distress calls of P. nathusii, P. pipistrellus and P. pygmaeus were structurally convergent, consisting of a series of downward-sweeping, frequency-modulated elements of short duration and high intensity with a relatively strong harmonic content. Selection may favour convergence in the structure of distress calls among bat species, if attracting heterospecifics increases the chance of repelling predators by mobbing.