ORCID Profile
0000-0002-9109-609X
Current Organisations
Australian National University
,
Monash University
,
Institute of Plasma Physics Chinese Academy of Sciences
,
University of Cambridge
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Ecology | Sociobiology And Behavioural Ecology | Behavioural Ecology
Biological sciences | Expanding Knowledge in the Biological Sciences |
Publisher: Springer Science and Business Media LLC
Date: 18-04-2015
Publisher: The Royal Society
Date: 02-09-2009
Abstract: Animals often form groups to increase collective vigilance and allow early detection of predators, but this benefit of sociality relies on rapid transfer of information. Among birds, alarm calls are not present in all species, while other proposed mechanisms of information transfer are inefficient. We tested whether wing sounds can encode reliable information on danger. In iduals taking off in alarm fly more quickly or ascend more steeply, so may produce different sounds in alarmed than in routine flight, which then act as reliable cues of alarm, or honest ‘index’ signals in which a signal's meaning is associated with its method of production. We show that crested pigeons, Ocyphaps lophotes , which have modified flight feathers, produce distinct wing ‘whistles’ in alarmed flight, and that in iduals take off in alarm only after playback of alarmed whistles. Furthermore, litude-manipulated playbacks showed that response depends on whistle structure, such as tempo, not simply litude. We believe this is the first demonstration that flight noise can send information about alarm, and suggest that take-off noise could provide a cue of alarm in many flocking species, with feather modification evolving specifically to signal alarm in some. Similar reliable cues or index signals could occur in other animals.
Publisher: Elsevier BV
Date: 08-2015
DOI: 10.1016/J.CUB.2015.06.028
Abstract: Many vertebrates gain critical information about danger by eavesdropping on other species' alarm calls [1], providing an excellent context in which to study information flow among species in animal communities [2-4]. A fundamental but unresolved question is how in iduals recognize other species' alarm calls. Although in iduals respond to heterospecific calls that are acoustically similar to their own, alarms vary greatly among species, and eavesdropping probably also requires learning [1]. Surprisingly, however, we lack studies demonstrating such learning. Here, we show experimentally that in idual wild superb fairy-wrens, Malurus cyaneus, can learn to recognize previously unfamiliar alarm calls. We trained in iduals by broadcasting unfamiliar sounds while simultaneously presenting gliding predatory birds. Fairy-wrens in the experiment originally ignored these sounds, but most fled in response to the sounds after two days' training. The learned response was not due to increased responsiveness in general or to sensitization following repeated exposure and was independent of sound structure. Learning can therefore help explain the taxonomic ersity of eavesdropping and the refining of behavior to suit the local community. In combination with previous work on unfamiliar predator recognition (e.g., [5]), our results imply rapid spread of anti-predator behavior within wild populations and suggest methods for training captive-bred animals before release into the wild [6]. A remaining challenge is to assess the importance and consequences of direct association of unfamiliar sounds with predators, compared with social learning-such as associating unfamiliar sounds with conspecific alarms.
Publisher: Wiley
Date: 09-04-2019
Publisher: Cambridge University Press
Date: 22-04-2004
Publisher: Oxford University Press (OUP)
Date: 30-06-2021
Abstract: Animals rely on both personal and social information about danger to minimize risk, yet environmental conditions constrain information. Both visual obstructions and background noise can reduce detectability of predators, which may increase reliance on social information, such as from alarm calls. Furthermore, a combination of visual and auditory constraints might greatly increase reliance on social information, because the loss of information from one source cannot be compensated by the other. Testing these possibilities requires manipulating personal information while broadcasting alarm calls. We therefore experimentally tested the effects of a visual barrier, traffic noise, and their combination on the response of Australian magpies, Cracticus tibicen, to heterospecific alarm calls. The barrier blocked only visual cues, while playback of moderate traffic noise could mask subtle acoustic cues of danger, such as of a predator’s movement, but not the alarm-call playback. We predicted that response to alarm calls would increase with either visual or acoustic constraint, and that there would be a disproportionate response when both were present. As predicted, in iduals responded more strongly to alarm calls when there was a visual barrier. However, moderate traffic noise did not affect responses, and the effect of the visual barrier was not greater during traffic-noise playback. We conclude that a reduction of personal, visual information led to a greater reliance on social information from alarm calls, confirming indirect evidence from other species. The absence of a traffic-noise effect could be because in Australian magpies hearing subtle cues is less important than vision in detecting predators.
Publisher: CSIRO Publishing
Date: 2008
DOI: 10.1071/ZO08049
Abstract: Duetting and female vocalisations have rarely been studied in tropical non-passerines. In coucals, a subfamily of nesting cuckoos, these behaviours have evolved under unusual conditions of male-biased parental care and reversed sexual size dimorphism. Here we provide the first detailed description of the structure and occurrence of sex-specific calls and duets in a monogamous coucal species, the pheasant coucal, Centropus phasianinus. Pheasant coucals of either sex use two types of far-reaching ( km) calls in their solo and duet displays: the ‘descending whoops’ call and, less frequently (25%), ‘scale’ calls. Both calls are series of very deep hooting notes that the larger females produce at lower frequency than the males (~326 versus 480 Hz). Descending whoops calls also vary among in iduals but this difference is not consistent enough for in idual identification. Most duets (63%) comprise a single scale call by each partner and the sexes start duets with equal frequency. Duetting triggers neighbouring pairs to duet too, suggesting a role in territory defence. Calling is most intense in the morning and early in the breeding season. The cryptic behaviour of coucals makes their calls an important tool for studies on their mating system, survey work and taxonomic research.
Publisher: Springer Science and Business Media LLC
Date: 10-05-2011
DOI: 10.1007/S00442-011-2002-4
Abstract: Generally in birds, the classic sex roles of male competition and female choice result in females providing most offspring care while males face uncertain parentage. In less than 5% of species, however, reversed courtship sex roles lead to predominantly male care and low extra-pair paternity. These role-reversed species usually have reversed sexual size dimorphism and polyandry, confirming that sexual selection acts most strongly on the sex with the smaller parental investment and accordingly higher potential reproductive rate. We used parentage analyses and observations from three field seasons to establish the social and genetic mating system of pheasant coucals, Centropus phasianinus, a tropical nesting cuckoo, where males are much smaller than females and provide most parental care. Pheasant coucals are socially monogamous and in this study males produced about 80% of calls in the dawn chorus, implying greater male sexual competition. Despite the substantial male investments, extra-pair paternity was unusually high for a socially monogamous, duetting species. Using two or more mismatches to determine extra-pair parentage, we found that 11 of 59 young (18.6%) in 10 of 21 broods (47.6%) were not sired by their putative father. Male incubation, starting early in the laying sequence, may give the female opportunity and reason to seek these extra-pair copulations. Monogamy, rather than the polyandry and sex-role reversal typical of its congener, C. grillii, may be the result of the large territory size, which could prevent females from monopolising multiple males. The pheasant coucal's exceptional combination of classic sex-roles and male-biased care for extra-pair young is hard to reconcile with current sexual selection theory, but may represent an intermediate stage in the evolution of polyandry or an evolutionary remnant of polyandry.
Publisher: The Royal Society
Date: 09-03-2022
Abstract: Most studies of acoustic communication focus on short units of vocalization such as songs, yet these units are often hierarchically organized into higher-order sequences and, outside human language, little is known about the drivers of sequence structure. Here, we investigate the organization, transmission and function of vocal sequences sung by male Albert's lyrebirds ( Menura alberti ), a species renowned for vocal imitations of other species. We quantified the organization of mimetic units into sequences, and examined the extent to which these sequences are repeated within and between in iduals and shared among populations. We found that in idual males organized their mimetic units into stereotyped sequences. Sequence structures were shared within and to a lesser extent among populations, implying that sequences were socially transmitted. Across the entire species range, mimetic units were sung with immediate variety and a high acoustic contrast between consecutive units, suggesting that sequence structure is a means to enhance receiver perceptions of repertoire complexity. Our results provide evidence that higher-order sequences of vocalizations can be socially transmitted, and that the order of vocal units can be functionally significant. We conclude that, to fully understand vocal behaviours, we must study both the in idual vocal units and their higher-order temporal organization.
Publisher: European Respiratory Society (ERS)
Date: 20-12-2019
DOI: 10.1183/13993003.01302-2019
Abstract: The multiple breath nitrogen washout (N 2 MBW) technique is increasingly used to assess the degree of ventilation inhomogeneity in school-aged children with lung disease. However, reference values for healthy children are currently not available. The aim of this study was to generate reference values for N 2 MBW outcomes in a cohort of healthy Caucasian school-aged children. N 2 MBW data from healthy Caucasian school-age children between 6 and 18 years old were collected from four experienced centres. Measurements were performed using an ultrasonic flowmeter (Exhalyzer D, Eco Medics AG, Duernten, Switzerland) and were analysed with commercial software (Spiroware version 3.2.1, Eco Medics AG). Normative values and upper limits of normal (ULN) were generated for lung clearance index (LCI) at 2.5% (LCI 2.5% ) and at 5% (LCI 5% ) of the initial nitrogen concentration and for moment ratios (M 1 /M 0 and M 2 /M 0 ). A prediction equation was generated for functional residual capacity (FRC). Analysis used 485 trials from 180 healthy Caucasian children aged from 6 to 18 years old. While LCI increased with age, this increase was negligible (0.04 units·year –1 for LCI 2.5% ) and therefore fixed ULN were defined for this age group. These limits were 7.91 for LCI 2.5% , 5.73 for LCI 5% , 1.75 for M 1 /M 0 and 6.15 for M 2 /M 0 , respectively. Height and weight were found to be independent predictors of FRC. We report reference values for N 2 MBW outcomes measured on a commercially available ultrasonic flowmeter device (Exhalyzer D, Eco Medics AG) in healthy school-aged children to allow accurate interpretation of ventilation distribution outcomes and FRC in children with lung disease.
Publisher: The Royal Society
Date: 13-07-2022
Abstract: The spatial distribution of cooperating in iduals plays a strategic role in territorial interactions of many group-living animals, and can indicate group cohesion. Vocalizations are commonly used to judge the distribution of signallers, but the spatial resolution of sounds is poor. Many species therefore accompany calls with movement however, little is known about the role of audio-visual perception in natural interactions. We studied the effect of angular separation on the efficacy of multimodal duets in the Australian magpie-lark, Grallina cyanoleuca . We tested specifically whether conspicuous wing movements, which typically accompany duets, affect responses to auditory angular separation. Multimodal playbacks of duets using robotic models and speakers showed that birds relied primarily on acoustic cues when visual and auditory angular separations were congruent, but used both modalities to judge separation between the signallers when modalities were spatially incongruent. The visual component modified the effect of acoustic separation: robotic models that were apart weakened the response when speakers were together, while models that were together strengthened responses when speakers were apart. Our results show that responses are stronger when signallers are together, and suggest that males were are able to bind information cross-modally on the senders' spatial location, which is consistent with a multisensory illusion.
Publisher: Elsevier BV
Date: 06-2010
DOI: 10.1016/J.YMPEV.2010.02.005
Abstract: The Meliphagoidea comprises the largest radiation of Australasian passerines. Here we present the first detailed molecular phylogenetic analysis of its families and genera, particularly the Acanthizidae, using sequences from nine gene regions including both mitochondrial and nuclear DNA. Our results support some suggested relationships but challenge other groupings, particularly in Meliphagidae and Acanthizidae. Maluridae is sister to all other members of the superfamily. With appropriate taxon s ling and multilocus data, we provide the first strong molecular evidence supporting earlier recognition of bristlebirds, Dasyornis, as a separate family, Dasyornithidae. We further clarify its position as sister to Acanthizidae+Pardalotidae+Meliphagidae. Pardalotidae is sister to Acanthizidae, and thus its retention as a separate family is arbitrary. The meliphagid genus Lichenostomus is polyphyletic. We find no support for the current subfamily structure within Acanthizidae but recognise a clade that includes members of the subfamily Sericornithinae excluding Oreoscopus and Acanthornis. Subfamily Acanthizinae is paraphyletic. Surprisingly, the Tasmanian island endemic Acanthornis magna of mesic habitats is sister to the Aphelocephala whitefaces of mainland Australian xeric zones. This is one of several unexpected alignments of taxa as sisters that probably reflects the age of the Meliphagoidea. We find no evidence for separate radiations of New Guinean and Australian members of the Meliphagoidea.
Publisher: Wiley
Date: 30-10-2022
DOI: 10.1111/DDI.13646
Abstract: Conservation has recently shifted to include behavioural or cultural ersity, adding substantial value to conservation efforts. Habitat loss and fragmentation can deplete ersity in learnt behaviours such as bird song by reducing the availability of song tutors, yet these impacts are poorly understood. Vocal mimicry may be particularly sensitive to habitat loss and fragmentation through the resulting reduction in both heterospecific models and conspecific tutors. Here we examine the relationship between habitat availability and both mimetic repertoire size and song composition in male Albert's lyrebirds ( Menura alberti ), a near‐threatened species renowned for its remarkable mimetic abilities. Eastern Australia. We calculated repertoire size and composition from recordings of male Albert's lyrebirds from throughout the species' range. We estimated patch size and local habitat availability using a species distribution model and remotely sensed vegetation types. We assessed the local model species assemblage through species distribution models and automated acoustic detectors. In idual males in smaller habitat patches, or in areas with a lower proportion of suitable habitat, mimicked fewer model species and fewer vocalization types. However, they mimicked comparatively more vocalizations from each model species than in iduals in larger patches or with more intact habitats. All model species were likely to occur in most study sites, suggesting that repertoires are not driven by the availability of model species. Our results suggest that mimetic repertoire sizes are influenced by habitat availability through the number of lyrebird tutors. Further, in iduals in disturbed habitats may partially compensate for mimicking fewer species by mimicking more vocalizations from each species. This study supports the hypothesis that cultural ersity may be impoverished by habitat loss and fragmentation in a similar way to genetic ersity. Variation in song ersity may therefore indicate population health and highlight populations in particular need of conservation action.
Publisher: Informa UK Limited
Date: 11-12-2008
DOI: 10.1080/09540120802032627
Abstract: AIDS stigmas create significant barriers to HIV prevention, testing, and care and can become internalized by people living with HIV/AIDS. We developed a psychometric scale to measure internalized AIDS-related stigmas among people infected with HIV. Items were adapted from a psychometrically sound test of AIDS-related stigmas in the general population. Six items reflecting self-defacing beliefs and negative perceptions of people living with HIV/AIDS were responded to dichotomously, Agree/Disagree. Data collected from people living with HIV/AIDS in Cape Town South Africa (n=1068), Swaziland (n=1090), and Atlanta US (n=239) showed that the internalized AIDS Stigma Scale was internally consistent (overall alpha coefficient=0.75) and time stable (r=0.53). We also found evidence in support of the scale's convergent, discriminant, and criterion-related validity. The Internalized AIDS-Related Stigma Scale appears reliable and valid and may be useful for research and evaluation with HIV-positive populations across southern African and North American cultures.
Publisher: The Royal Society
Date: 23-12-2013
Abstract: Communication about predators can reveal the effects of both conspecific and heterospecific audiences on signalling strategy, providing insight into signal function and animal cognition. In species that alarm call to their young, parents face a fundamental dilemma: calling can silence noisy offspring and so make them less likely to be overheard, but can also alert predators that young are nearby. Parents could resolve this dilemma by being sensitive to the current vulnerability of offspring, and calling only when young are most at risk. Testing whether offspring vulnerability affects parental strategy has proved difficult, however, because more vulnerable broods are often also more valuable. We tested experimentally whether parent white-browed scrubwren, Sericornis frontalis , assessed brood noisiness when alarm calling near nests . When a model predator was nearby, parents gave more alarm calls when playbacks simulated noisy broods, yet brood noisiness did not affect adult calling when only a control model was present. Parents were therefore sensitive to the tradeoff between silencing young and alerting predators to the presence of nests. Our study demonstrates that receiver vulnerability can affect signalling decisions in species other than primates.
Publisher: Elsevier BV
Date: 06-2012
Publisher: The Royal Society
Date: 19-02-2020
Abstract: In the perpetual struggle between high-speed predators and their prey, in iduals need to react in the blink of an eye to avoid capture. Alarm calls that warn of danger therefore need to do so sufficiently rapidly that listeners can escape in time. Paradoxically, many species produce more elements in their alarm calls when signalling about more immediate danger, thereby increasing the reliability of transmission of critical information but taking longer to convey the urgent message. We found that New Holland honeyeaters, Phylidonyris novaehollandiae , incorporated more elements in alarm calls given to more dangerous predators, but video analysis revealed that listeners responded in 100 ms, after only the first element. Consistent with this rapid response, the acoustic structure of the first element varied according to the danger, and playbacks confirmed that birds need hear only the first element to assess risk. However, birds hid for longer and were more likely to flee, after calls with more elements. The dual mechanisms of varying both element structure and number may provide a widespread solution to signalling rapidly and reliably about immediate danger.
Publisher: Elsevier BV
Date: 08-2005
Publisher: The Royal Society
Date: 07-03-2013
Abstract: Vertebrates that eavesdrop on heterospecific alarm calls must distinguish alarms from sounds that can safely be ignored, but the mechanisms for identifying heterospecific alarm calls are poorly understood. While vertebrates learn to identify heterospecific alarms through experience, some can also respond to unfamiliar alarm calls that are acoustically similar to conspecific alarm calls. We used synthetic calls to test the role of specific acoustic properties in alarm call identification by superb fairy-wrens, Malurus cyaneus . In iduals fled more often in response to synthetic calls with peak frequencies closer to those of conspecific calls, even if other acoustic features were dissimilar to that of fairy-wren calls. Further, they then spent more time in cover following calls that had both peak frequencies and frequency modulation rates closer to natural fairy-wren means. Thus, fairy-wrens use similarity in specific acoustic properties to identify alarms and adjust a two-stage antipredator response. Our study reveals how birds respond to heterospecific alarm calls without experience, and, together with previous work using playback of natural calls, shows that both acoustic similarity and learning are important for interspecific eavesdropping. More generally, this study reconciles contrasting views on the importance of alarm signal structure and learning in recognition of heterospecific alarms.
Publisher: Oxford University Press (OUP)
Date: 17-07-2007
Publisher: Elsevier BV
Date: 11-2007
Publisher: Wiley
Date: 07-10-2020
DOI: 10.1111/ETH.13090
Publisher: Elsevier
Date: 2010
Publisher: Elsevier BV
Date: 07-2017
Publisher: The Royal Society
Date: 22-06-2015
Abstract: Animals often mimic dangerous or toxic species to deter predators however, mimicry of such species may not always be possible and mimicry of benign species seems unlikely to confer anti-predator benefits. We reveal a system in which a bird mimics the alarm calls of harmless species to fool a predator 40 times its size and protect its offspring against attack. Our experiments revealed that brown thornbills ( Acanthiza pusilla ) mimic a chorus of other species' aerial alarm calls, a cue of an Accipiter hawk in flight, when predators attack their nest. The absence of any flying predators in this context implies that these alarms convey deceptive information about the type of danger present. Experiments on the primary nest predators of thornbills, pied currawongs ( Strepera graculina ), revealed that the predators treat these alarms as if they themselves are threatened by flying hawks, either by scanning the sky for danger or fleeing, confirming a deceptive function. In turn, these distractions delay attack and provide thornbill nestlings with an opportunity to escape. This sophisticated defence strategy exploits the complex web of interactions among multiple species across several trophic levels, and in particular exploits a predator's ability to eavesdrop on and respond appropriately to heterospecific alarm calls. Our findings demonstrate that prey can fool predators by deceptively mimicking alarm calls of harmless species, suggesting that defensive mimicry could be more widespread because of indirect effects on predators within a web of eavesdropping.
Publisher: Elsevier BV
Date: 06-2003
Publisher: Elsevier BV
Date: 02-2010
Publisher: Elsevier BV
Date: 09-2003
Publisher: Elsevier BV
Date: 06-2013
DOI: 10.1016/J.CUB.2013.05.018
Abstract: All human cultures have music and dance, and the two activities are so closely integrated that many languages use just one word to describe both. Recent research points to a deep cognitive connection between music and dance-like movements in humans, fueling speculation that music and dance have coevolved and prompting the need for studies of audiovisual displays in other animals. However, little is known about how nonhuman animals integrate acoustic and movement display components. One striking property of human displays is that performers coordinate dance with music by matching types of dance movements with types of music, as when dancers waltz to waltz music. Here, we show that a bird also temporally coordinates a repertoire of song types with a repertoire of dance-like movements. During displays, male superb lyrebirds (Menura novaehollandiae) sing four different song types, matching each with a unique set of movements and delivering song and dance types in a predictable sequence. Crucially, display movements are both unnecessary for the production of sound and voluntary, because males sometimes sing without dancing. Thus, the coordination of independently produced repertoires of acoustic and movement signals is not a uniquely human trait.
Publisher: Elsevier BV
Date: 06-2018
Publisher: Wiley
Date: 07-2023
DOI: 10.1002/ECE3.10272
Abstract: Interceptive eavesdropping on the alarm calls of heterospecifics provides crucial information about predators. Previous research suggests predator discrimination, call relevance, reliability, and reception explain when eavesdropping will evolve. However, there has been no quantitative analysis to scrutinize these principles, or how they interact. We develop a mathematical framework that formalizes the study of the key principles thought to select for eavesdropping. Interceptive eavesdropping appears to be greatly affected by the threat faced by caller and eavesdropper, as well as presence of informational noise affecting the detection of calls and predators. Accordingly, our model uses signal detection theory to examine when selection will favor alarm calling by a sender species and fleeing by an eavesdropping receiver species. We find eavesdropping is most strongly selected when (1) the receiver faces substantial threats, (2) species are ecologically similar, (3) senders often correctly discriminate threats, (4) receivers often correctly perceive calls, and (5) the receiver's personal discrimination of threats is poor. Furthermore, we find (6) that very high predation levels can select against eavesdropping because prey cannot continuously flee and must conserve energy. Reliability of heterospecific calls for identifying threats is thought to be important in selecting for eavesdropping. Consequently, we formally define reliability, showing its connection to specificity and sensitivity, clarifying how these quantities can be measured. We find that high call relevance, due to similar vulnerability to predators between species, strongly favors eavesdropping. This is because senders trade‐off false alarms and missed predator detections in a way that is also favorable for the eavesdropper, by producing less of the costlier error. Unexpectedly, highly relevant calls increase the total number of combined errors and so have lower reliability. Expectedly, when noise greatly affects personally gathered cues to threats, but not heterospecific calls or detection of predators, eavesdropping is favored.
Publisher: Elsevier BV
Date: 06-2010
DOI: 10.1016/J.TREE.2010.01.002
Abstract: Acquiring information from the cues and signals of other species of the same trophic level is widespread among animals, and can help in iduals exploit resources and avoid predators. But can such interspecific information transfer also influence the spatial structure of species within communities? Whereas some species use heterospecific information without changing their position, we review research that indicates that heterospecific information is a driving factor in the formation or maintenance of temporary or stable mixed-species groups. Heterospecific information can also influence the organization of such groups, including leadership. Further, animals sometimes select habitats using heterospecific information. We survey interspecific information transfer, and evaluate the morphological, ecological and behavioral factors that make some species information sources and others information seekers.
Publisher: Elsevier BV
Date: 10-2015
Publisher: Oxford University Press (OUP)
Date: 2011
Publisher: Elsevier BV
Date: 05-2021
DOI: 10.1016/J.CUB.2021.02.003
Abstract: Darwin argued that females' "taste for the beautiful" drives the evolution of male extravagance,
Publisher: Oxford University Press (OUP)
Date: 06-2009
Publisher: The Royal Society
Date: 02-02-2011
Abstract: Begging by nestling birds has been used to test evolutionary models of signalling but theory has outstripped evidence. Eavesdropping predators potentially impose a cost on begging that ensures signal honesty, yet little experimental evidence exists for such a cost at active nests because the use of artificial nests, long playback bouts and absence of parents may have exaggerated costs. We broadcast short periods (1 h) of either nestling vocalizations or background noise at active white-browed scrubwren, Sericornis frontalis , nests. Nestlings called naturally during both treatments, allowing us to test whether elevated calling increases risk, a key but rarely tested assumption of evolutionary models. Predators visited nests exclusively during periods of elevated calling. Furthermore, playbacks affected neither adult visits nor nestling activity, suggesting that calling alone attracted predators. Adults gave alarm calls and nestlings usually called less when predators approached nests. Predation risk to broods is, therefore, likely to fluctuate substantially over short periods of time, depending on nestling hunger and whether adults or young have detected predators. This study confirms a present-day cost of nestling begging, demonstrates that this cost can be incurred over short periods and supports the importance of parent–offspring antipredator strategies in reducing predation risk.
Publisher: Wiley
Date: 14-02-2021
DOI: 10.1002/ECE3.7225
Publisher: AIP Publishing
Date: 05-2017
DOI: 10.1063/1.4982688
Abstract: In several tokamaks, non-axisymmetric magnetic field studies show that applied magnetic fields with a toroidal harmonic n = 2 can lead to disruptive n = 1 locked modes. In Ohmic plasmas, n = 2 magnetic reconnection thresholds in otherwise stable discharges are readily accessed at edge safety factors q ∼ 3, low density, and low rotation. Similar to previous studies with n = 1 fields, the thresholds are correlated with the “overlap” field computed with the IPEC code. The overlap field quantifies the plasma-mediated coupling of the external field to the resonant field. Remarkably, the “critical overlap fields” at which magnetic islands form are similar for applied n = 1 and 2 fields. The critical overlap field increases with plasma density and edge safety factor but is independent of the toroidal field. Poloidal harmonics m & nq dominate the drive for resonant fields while m & nq harmonics have a negligible impact. This contrasts with previous results in H-mode discharges at high plasma pressure in which the toroidal angular momentum is sensitive to low poloidal harmonics. Together, these results highlight unique requirements for n & 1 field control including the need for multiple rows of coils to control selected plasma parameters for specific functions (e.g., rotation control or ELM suppression).
Publisher: The Royal Society
Date: 11-11-2009
Abstract: Alarm calls given by other species potentially provide a network of information about danger, but little is known about the role of acoustic similarity compared with learning in recognition of heterospecific calls. In particular, the aerial ‘hawk’ alarm calls of passerines provide a textbook ex le of signal design because many species have converged on a design that thwarts eavesdropping by hawks, and call similarity might therefore allow recognition. We measured the response of fairy-wrens ( Malurus cyaneus ) to playback of acoustically similar scrubwren ( Sericornis frontalis ) aerial alarm calls. First, if call similarity prompts escape independent of learning, then fairy-wrens should flee to playback of scrubwren calls outside their geographical range. However, fairy-wrens fled only in sympatry. Second, if call similarity is necessary for learning heterospecific calls, then fairy-wrens should not respond to sympatric species with different calls. We found, on the contrary, that fairy-wrens fled to the very different aerial alarm calls of a honeyeater ( Phylidonyris novaehollandiae ). Furthermore, response to the honeyeater depended on the specific structure of the call, not acoustic similarity. Overall, call similarity was neither sufficient nor necessary for interspecific recognition, implying learning is essential in the complex task of sifting the acoustic world for cues about danger.
Publisher: Elsevier BV
Date: 12-2012
Publisher: The Royal Society
Date: 27-03-2019
Abstract: Information about predators can mean the difference between life and death, but prey face the challenge of integrating personal information about predators with social information from the alarm calls of others. This challenge might even affect the structure of interspecific information networks: species vary in response to alarm calls, potentially because different foraging ecologies constrain the acquisition of personal information. However, the hypothesis that constrained personal information explains a greater response to alarm calls has not been experimentally tested. We used a within-species test to compare the antipredator responses of New Holland honeyeaters, Phylidonyris novaehollandiae , during contrasting foraging behaviour. Compared with perched birds, which hawk for insects and have a broad view, those foraging on flowers were slower to spot gliding model predators, showing that foraging behaviour can affect predator detection. Furthermore, nectar-foraging birds were more likely to flee to alarm call playbacks. Birds also assessed social information relevance: more distant calls, and those from another species, prompted fewer flights and slower reaction times. Overall, birds made flexible decisions about danger by integrating personal and social information, while weighing information relevance. These findings support the idea that a strategic balance of personal and social information could affect community function.
Publisher: Elsevier BV
Date: 07-2016
Publisher: Springer Science and Business Media LLC
Date: 04-2023
Publisher: Elsevier BV
Date: 06-2022
Publisher: Springer Science and Business Media LLC
Date: 30-09-2023
Publisher: Elsevier BV
Date: 06-2007
Publisher: Wiley
Date: 11-06-2014
DOI: 10.1111/BRV.12122
Abstract: Animals often gather information from other species by eavesdropping on signals intended for others. We review the extent, benefits, mechanisms, and ecological and evolutionary consequences of eavesdropping on other species' alarm calls. Eavesdropping has been shown experimentally in about 70 vertebrate species, and can entail closely or distantly related species. The benefits of eavesdropping include prompting immediate anti-predator responses, indirect enhancement of foraging or changed habitat use, and learning about predators. Eavesdropping on heterospecifics can provide more eyes looking for danger, complementary information to that from conspecifics, and potentially information at reduced cost. The response to heterospecific calls can be unlearned or learned. Unlearned responses occur when heterospecific calls have acoustic features similar to that used to recognize conspecific calls, or acoustic properties such as harsh sounds that prompt attention and may allow recognition or facilitate learning. Learning to recognize heterospecific alarm calls is probably essential to allow recognition of the ersity of alarm calls, but the evidence is largely indirect. The value of eavesdropping on different species is affected by problems of signal interception and the relevance of heterospecific alarm calls to the listener. These constraints on eavesdropping will affect how information flows among species and thus affect community function. Some species are 'keystone' information producers, while others largely seek information, and these differences probably affect the formation and function of mixed-species groups. Eavesdroppers might also integrate alarm calls from multiple species to extract relevant and reliable information. Eavesdropping appears to set the stage for the evolution of interspecific deception and communication, and potentially affects communication within species. Overall, we now know that eavesdropping on heterospecific alarm calls is an important source of information for many species across the globe, and there are le opportunities for research on mechanisms, fitness consequences and implications for community function and signalling evolution.
Publisher: Elsevier BV
Date: 05-2022
Publisher: Wiley
Date: 23-12-2020
DOI: 10.1111/AEC.12993
Publisher: The Royal Society
Date: 18-05-2020
Abstract: In a pioneering study of signal design, Marler (Marler 1955 Nature 176 , 6–8. ( doi:10.1038/176006a0 ) Marler 1957 Behaviour 11 , 13–37. ( doi:10.1163/156853956X00066 )) argued that the contrasting acoustic design of hawk (seet) and mobbing alarm calls of European passerines reflected their contrasting function. Hawk alarms were high-frequency tones, warning conspecifics to flee but making localization difficult for predators, while mobbing calls were broadband and harsh, allowing easy localization and approach. Contrasting signal features are also consistent with signal detection theory. Discriminating these calls quickly is critical for survival, because hawk alarms require immediate escape. These signals should therefore be selected to be easy to discriminate, reducing the trade-off between immediate fleeing to hawk alarms and unnecessary fleeing to mobbing alarms. Despite these expectations, hawk and mobbing alarm calls of superb fairy-wrens, Malurus cyaneus , are surprisingly similar, raising the question of discriminability without contextual cues. We synthesized these calls on computer, made intermediates and used playbacks to test whether calls can be discriminated acoustically, and if so by what features. We found that birds used multiple acoustic features when discriminating calls, allowing fast discrimination despite overlap in in idual parameters. We speculate that the similarity of fairy-wren alarm calls could enhance detectability of both signals, while multiple subtle acoustic differences reduce a trade-off with discriminability. This article is part of the theme issue ‘Signal detection theory in recognition systems: from evolving models to experimental tests'.
Publisher: Wiley
Date: 30-07-2014
DOI: 10.1111/BRV.12129
Abstract: Mimicry is a classical ex le of adaptive signal design. Here, we review the current state of research into vocal mimicry in birds. Avian vocal mimicry is a conspicuous and often spectacular form of animal communication, occurring in many distantly related species. However, the proximate and ultimate causes of vocal mimicry are poorly understood. In the first part of this review, we argue that progress has been impeded by conceptual confusion over what constitutes vocal mimicry. We propose a modified version of Vane-Wright's (1980) widely used definition of mimicry. According to our definition, a vocalisation is mimetic if the behaviour of the receiver changes after perceiving the acoustic resemblance between the mimic and the model, and the behavioural change confers a selective advantage on the mimic. Mimicry is therefore specifically a functional concept where the resemblance between heterospecific sounds is a target of selection. It is distinct from other forms of vocal resemblance including those that are the result of chance or common ancestry, and those that have emerged as a by-product of other processes such as ecological convergence and selection for large song-type repertoires. Thus, our definition provides a general and functionally coherent framework for determining what constitutes vocal mimicry, and takes account of the ersity of vocalisations that incorporate heterospecific sounds. In the second part we assess and revise hypotheses for the evolution of avian vocal mimicry in the light of our new definition. Most of the current evidence is anecdotal, but the erse contexts and acoustic structures of putative vocal mimicry suggest that mimicry has multiple functions across and within species. There is strong experimental evidence that vocal mimicry can be deceptive, and can facilitate parasitic interactions. There is also increasing support for the use of vocal mimicry in predator defence, although the mechanisms are unclear. Less progress has been made in explaining why many birds incorporate heterospecific sounds into their sexual displays, and in determining whether these vocalisations are functionally mimetic or by-products of sexual selection for other traits such as repertoire size. Overall, this discussion reveals a more central role for vocal mimicry in the behavioural ecology of birds than has previously been appreciated. The final part of this review identifies important areas for future research. Detailed empirical data are needed on in idual species, including on the structure of mimetic signals, the contexts in which mimicry is produced, how mimicry is acquired, and the ecological relationships between mimic, model and receiver. At present, there is little information and no consensus about the various costs of vocal mimicry for the protagonists in the mimicry complex. The ersity and complexity of vocal mimicry in birds raises important questions for the study of animal communication and challenges our view of the nature of mimicry itself. Therefore, a better understanding of avian vocal mimicry is essential if we are to account fully for the ersity of animal signals.
Publisher: Elsevier BV
Date: 08-2018
DOI: 10.1016/J.CUB.2018.06.013
Abstract: Animals in natural communities gain information from members of other species facing similar ecological challenges [1-5], including many vertebrates that recognize the alarm calls of heterospecifics vulnerable to the same predators [6]. Learning is critical in explaining this widespread recognition [7-13], but there has been no test of the role of social learning in alarm-call recognition, despite the fact that it is predicted to be important in this context [14, 15]. We show experimentally that wild superb fairy-wrens, Malurus cyaneus, learn socially to recognize new alarm calls and can do so through the previously undemonstrated mechanism of acoustic-acoustic association of unfamiliar with known alarm calls. Birds were trained in the absence of any predator by broadcasting unfamiliar sounds, to which they did not originally flee, in combination with a chorus of conspecific and heterospecific aerial alarm calls (typically given to hawks in flight). The fairy-wrens responded to the new sounds after training, usually by fleeing to cover, and responded equally as strongly in repeated tests over a week. Control playbacks showed that the response was not due simply to greater wariness. Fairy-wrens therefore learnt to associate new calls with known alarm calls, without having to see the callers or a predator. This acoustic-acoustic association mechanism of social learning could result in the rapid spread of alarm-call recognition in natural communities, even when callers or predators are difficult to observe. Moreover, this mechanism offers potential for use in conservation by enhancing training of captive-bred in iduals before release into the wild.
Publisher: Elsevier BV
Date: 04-2023
Publisher: AIP Publishing
Date: 30-04-2014
DOI: 10.1063/1.4872195
Abstract: A long-pulse high confinement plasma regime known as H-mode is achieved in the Experimental Advanced Superconducting Tokamak (EAST) with a record duration over 30 s, sustained by Lower Hybrid wave Current Drive (LHCD) with advanced lithium wall conditioning and ertor pumping. This long-pulse H-mode plasma regime is characterized by the co-existence of a small Magneto-Hydrodynamic (MHD) instability, i.e., Edge Localized Modes (ELMs) and a continuous quasi-coherent MHD mode at the edge. We find that LHCD provides an intrinsic boundary control for ELMs, leading to a dramatic reduction in the transient power load on the vessel wall, compared to the standard Type I ELMs. LHCD also induces edge plasma ergodization, broadening heat deposition footprints, and the heat transport caused by ergodization can be actively controlled by regulating edge plasma conditions, thus providing a new means for stationary heat flux control. In addition, advanced tokamak scenarios have been newly developed for high-performance long-pulse plasma operations in the next EAST experimental c aign.
Publisher: The Royal Society
Date: 22-06-2004
Publisher: Elsevier BV
Date: 12-2020
Publisher: The Royal Society
Date: 04-10-2017
Abstract: Many group-living animals cooperatively signal to defend resources, but what stops deceptive signalling to competitors about coalition strength? Cooperative-signalling species include mated pairs of birds that sing duets to defend their territory. In iduals of these species sometimes sing ‘pseudo-duets’ by mimicking their partner's contribution, but it is unknown if these songs are deceptive, or why duets are normally reliable. We studied pseudo-duets in Australian magpie-larks, Grallina cyanoleuca , and tested whether multimodal signalling constrains deception. Magpie-larks give antiphonal duets coordinated with a visual display, with each sex typically choosing a different song type within the duet. In iduals produced pseudo-duets almost exclusively during nesting when partners were apart, but the two song types were used in sequence rather than antiphonally. Strikingly, birds hid and gave no visual displays, implying deceptive suppression of information. Acoustic playbacks showed that pseudo-duets provoked the same response from residents as true duets, regardless of whether they were sequential or antiphonal, and stronger response than that to true duets consisting of a single song type. By contrast, experiments with robot models showed that songs accompanied by movements of two birds prompted stronger responses than songs accompanied by movements of one bird, irrespective of the number of song types or singers. We conclude that magpie-larks used deceptive pseudo-duets when partners were apart, and suppressed the visual display to maintain the subterfuge. We suggest that the visual component of many species' duets provides the most reliable information about the number of signallers and may have evolved to maintain honesty in duet communication.
Publisher: The Royal Society
Date: 29-06-2006
Abstract: Young birds and mammals are extremely vulnerable to predators and so should benefit from responding to parental alarm calls warning of danger. However, young often respond differently from adults. This difference may reflect: (i) an imperfect stage in the gradual development of adult behaviour or (ii) an adaptation to different vulnerability. Altricial birds provide an excellent model to test for adaptive changes with age in response to alarm calls, because fledglings are vulnerable to a different range of predators than nestlings. For ex le, a flying hawk is irrelevant to a nestling in a enclosed nest, but is dangerous to that in idual once it has left the nest, so we predict that young develop a response to aerial alarm calls to coincide with fledging. Supporting our prediction, recently fledged white-browed scrubwrens, Sericornis frontalis , fell silent immediately after playback of their parents' aerial alarm call, whereas nestlings continued to calling despite hearing the playback. Young scrubwrens are therefore exquisitely adapted to the changing risks faced during development.
Publisher: Oxford University Press (OUP)
Date: 2014
Publisher: The Royal Society
Date: 28-06-2017
Abstract: Increased predation risk is considered a cost of having conspicuous colours, affecting the anti-predator behaviour of colourful animals. However, this is difficult to test, as in idual factors often covary with colour and behaviour. We used alarm call playback and behavioural observations to assess whether in idual birds adjust their response to risk according to their plumage colour. Male superb fairy-wrens ( Malurus cyaneus ) change from a dull brown to conspicuous blue plumage each year, allowing the behaviour of different coloured birds to be compared while controlling for within-in idual effects. Because the timing of colour change varies among males, blue and brown birds can also be compared at the same time of year, controlling for seasonal effects on behaviour. While blue, fairy-wrens fled more often in response to alarm calls, and took longer to emerge from cover. Blue fairy-wrens also spent more time foraging in cover and being vigilant. Group members appeared to benefit from the presence of blue males, as they reduced their response to alarms, and allocated less time to sentinel behaviour when a blue male was close by. We suggest that fairy-wrens perceive themselves to be at a higher risk of predation while in conspicuous plumage and adjust their behaviour accordingly.
Publisher: Elsevier BV
Date: 03-2013
Publisher: CSIRO Publishing
Date: 2004
DOI: 10.1071/ZO04013
Abstract: The 'status-signalling' hypothesis states that in iduals might avoid unprofitable fights by signalling their competitive ability and assessing the signals of others. The frontal shields of rails (Aves : Rallidae) are fleshy structures that are displayed prominently during agonistic interactions. Shield maintenance probably requires elevated levels of testosterone and deposition of carotenoid pigments, which implies that shield size and colour could be honest signals of the ability or willingness to fight. We used field observations and a model experiment to study the signalling function of the red shield of the dusky moorhen, Gallinula tenebrosa. Birds with relatively larger shields were more likely to win aggressive encounters, and the outcome was apparently unaffected, or less strongly affected, by body size, weight, condition and sex. Shield size increased with body size and weight, but neither explained more than 26% of the variation in shield size, even after controlling for age and date. Shield size was not affected by body condition, as estimated from residuals of a regression of weight on body size. Moorhens confronted with a model fitted with a large shield retreated more quickly than they did when presented with the same model bearing a small shield, supporting the results from natural interactions. We conclude that the frontal shield functions as a signal during agonistic interactions, and possibly signals the ability or willingness to fight.
Publisher: Informa UK Limited
Date: 13-05-2022
DOI: 10.1080/13548506.2022.2075020
Abstract: Social distancing behaviour is a primary preventive measure for reducing COVID-19 transmission. Improved understanding of factors associated with adherence to social distancing is vital for mitigating the impact of COVID-19 in South Africa. The study assessed adherence to social distancing and its associated factors during the state-implemented lockdown in South Africa. Data was analysed from a large-scale public survey conducted in South Africa from 8 to 29 April 2020, which was administered online and telephonically. Invitations to participate were distributed widely on local websites and social media networks, including on a data-free platform. Adherence to social distancing was measured by self-report of having engaged in close physical contact with someone outside the home. Simple and multiple logistic regression models examined the association between social distancing and potential explanatory variables. Of the 17,586 participants, 9.2% came into close physical contact with a person outside their home by hugging, kissing, or shaking hands during the past 7 days. The odds of coming into close physical contact with other people were significantly higher for males, students, and those with incorrect knowledge on physical distancing, angry attitudes about the lockdown, lack of confidence in the government response, high-risk perception, movement out of the local area, travelling to shops using public transport, households with communal water facilities and higher household size. The 25-59-year olds compared to 18-24-year olds, and the White and Indian/Asian compared to the African population groups had significantly lower odds of close physical contact with others outside the home. The study identifies subgroups of in iduals for whom public health interventions to improve adherence to social distancing should be prioritised and tailored. Interventions and policies should take cognisance of the social determinants of health as well as culturally accepted greeting practices like hand shaking.
Publisher: Elsevier BV
Date: 04-2004
Publisher: Elsevier BV
Date: 02-2010
Publisher: Elsevier BV
Date: 05-2003
Publisher: Elsevier BV
Date: 06-2018
Publisher: Elsevier BV
Date: 02-2013
Publisher: The Royal Society
Date: 27-05-2005
Abstract: Vertebrate alarm calls can contain information about the type of predator and the degree of danger, but young animals often respond to alarm calls differently from adults. The distinct behaviour of young may reflect an imperfect stage in the gradual development of the adult response, or a response adapted to specific risks faced by young. In this study, we tested whether nestling white-browed scrubwrens, Sericornis frontalis , responded to different alarm calls according to their specific risks of predation. As predators on the ground pose a danger to scrubwren nestlings, whereas flying predators do not, we predicted that they would respond to ground alarm calls but not to aerial alarm calls. In a field playback experiment, we tested the response of young to aerial and ground alarm calls, each presented in a shorter (less urgent) and longer (more urgent) form. We found that both 5- and 11-day-old nestlings responded to ground alarm calls, and did so more strongly to the more urgent playback. By contrast, the response to aerial alarm calls started to develop only towards the end of the nestling stage. Thus, scrubwren nestlings can distinguish between different types of alarm calls and react more strongly to calls warning of a predator posing greater danger, appropriate to the nestling stage of development. Furthermore, they use the length of ground alarm calls as an indicator of the degree of danger.
Publisher: Elsevier BV
Date: 04-2004
Publisher: Elsevier BV
Date: 02-2019
Publisher: Springer International Publishing
Date: 2020
Publisher: Wiley
Date: 22-12-2014
DOI: 10.1111/JAV.00622
Publisher: The Company of Biologists
Date: 15-12-2011
DOI: 10.1242/JEB.061614
Abstract: Habituation is an active process that allows animals to learn to identify repeated, harmless events, and so could help in iduals deal with the trade-off between reducing the risk of predation and minimizing escape costs. Safe habituation requires an accurate distinction between dangerous and harmless events, but in natural environments such an assessment is challenging because sensory information is often noisy and limited. What, then, comprises the information animals use to recognize objects that they have previously learned to be harmless? We tested whether the fiddler crab Uca vomeris distinguishes objects purely by their sensory signature or whether identification also involves more complex attributes such as the direction from which an object approaches. We found that crabs habituated their escape responses after repeated presentations of a dummy predator consistently approaching from the same compass direction. Females habituated both movement towards the burrow and descent into the burrow, whereas males only habituated descent into the burrow. The crabs were more likely to respond again when a physically identical dummy approached them from a new compass direction. The crabs distinguished between the two dummies even though both dummies were visible for the entire duration of the experiment and there was no difference in the timing of the dummies' movements. Thus, the position or approach direction of a dummy encodes important information that allows animals to identify an event and habituate to it. These results argue against the traditional notion that habituation is a simple, non-associative learning process, and instead suggest that habituation is very selective and uses information to distinguish between objects that is not available from the sensory signature of the object itself.
Publisher: The Royal Society
Date: 17-08-2011
Abstract: Many vertebrates eavesdrop on alarm calls of other species, which is a remarkable ability, given geographical variation in community composition and call ersity within and among species. We used micro-geographical variation in community composition to test whether in iduals recognize heterospecific alarm calls by: (i) responding to acoustic features shared among alarm calls (ii) having innate responses to particular heterospecific calls or (iii) learning specific alarm calls. We found that superb fairy-wrens ( Malurus cyaneus ) fled to cover to playback of noisy miner ( Manorina melanocephala ) aerial predator alarm calls only in locations where miners were present, suggesting that learning rather than acoustic structure determines response. Sites with and without miners were well within the dispersal distance of fairy-wrens, and philopatric males and dispersing females showed the same pattern, so that local genetic adaptation is extremely unlikely. Furthermore, where miners were present, fairy-wrens responded appropriately to different miner calls, implying eavesdropping on their signalling system rather than fleeing from miners themselves. Learned eavesdropping on alarm calls enables in iduals to harvest ecologically relevant information from heterospecifics on an astonishingly fine spatial scale. Such phenotypic plasticity is valuable in a changing world, where in iduals can be exposed to new species.
Publisher: Springer Science and Business Media LLC
Date: 11-07-2017
Location: No location found
Location: China
Location: United Kingdom of Great Britain and Northern Ireland
Start Date: 05-2015
End Date: 12-2019
Amount: $469,600.00
Funder: Australian Research Council
View Funded ActivityStart Date: 2003
End Date: 12-2005
Amount: $165,000.00
Funder: Australian Research Council
View Funded ActivityStart Date: 2006
End Date: 12-2009
Amount: $239,000.00
Funder: Australian Research Council
View Funded Activity