ORCID Profile
0000-0002-5825-3591
Current Organisation
La Trobe University
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Sociobiology And Behavioural Ecology | Evolutionary Biology | Zoology | Animal Behaviour | Sensory Systems | Neural Networks, Genetic Alogrithms And Fuzzy Logic | Behavioural Ecology
Biological sciences | Expanding Knowledge in the Biological Sciences |
Publisher: Wiley
Date: 10-2003
Publisher: Elsevier BV
Date: 03-2008
Publisher: Frontiers Media SA
Date: 03-2017
Publisher: Informa UK Limited
Date: 28-07-2022
Publisher: Springer Berlin Heidelberg
Date: 2013
Publisher: Elsevier BV
Date: 02-2015
Publisher: Royal Society of Chemistry (RSC)
Date: 2013
DOI: 10.1039/C3CC90365F
Publisher: Oxford University Press (OUP)
Date: 05-08-2016
Publisher: Elsevier BV
Date: 02-2009
Publisher: Springer Science and Business Media LLC
Date: 24-03-2009
Publisher: The Company of Biologists
Date: 10-2015
DOI: 10.1242/JEB.127605
Abstract: Reduced vigilance is the conspicuous cost of sleep in most animals. To mitigate against this cost, some birds and aquatic mammals have evolved the ability to sleep with one-half of their brain at a time, a phenomenon known as unihemispheric sleep. During unihemispheric sleep the eye neurologically connected to the ‘awake’ hemisphere remains open while the other eye is closed. Such unilateral eye closure (UEC) has been observed across avian and non-avian reptiles, but has received little attention in the latter. Here, we explored the use of UEC in juvenile saltwater crocodiles (1) under baseline conditions, and in the presence of (2) other young crocodiles and (3) a human. Crocodiles increased the amount of UEC in response to the human, and preferentially oriented their open eye towards both stimuli. These results are consistent with observations on unihemispherically sleeping cetaceans and birds, and could have implications for our understanding of the evolution of unihemispheric sleep.
Publisher: Elsevier BV
Date: 07-2007
Publisher: Unpublished
Date: 2013
Publisher: Springer Science and Business Media LLC
Date: 09-02-2008
Publisher: The Company of Biologists
Date: 02-2007
DOI: 10.1242/JEB.02676
Abstract: The efficacy of any animal signal is constrained by the range over which it remains above the sensory threshold of potential receivers. The spatial area in which reliable detection occurs defines active space this is influenced by signal structure, the signalling environment and the sensory characteristics of receivers. Identification of the factors influencing active space has provided valuable insights into signal design, particularly in bioacoustics,in which signal distortion and degradation can be easily quantified. In the present study, we consider whether active space can similarly help to explain the design of a movement-based visual signal. The Jacky dragon(Amphibolurus muricatus) threat display is composed of five distinct motor patterns delivered in an obligatory sequence: tail-flicks, backward and forward foreleg waves, a push-up and a `body-rock'. In contrast to other communication systems, the introductory element is characterized by reduced intensity (average speed) but greater duration than subsequent motor patterns. Furthermore, the tail-flick sweeps a three-dimensional (3D) space around the lizard, whereas the motor patterns that follow are largely restricted to a single plane. Structural properties thus suggest that the active space of the tail-flick might be greater than that of the other motor patterns in the display, which would provide a parsimonious explanation for its use as an alerting component. We tested this prediction in a playback experiment incorporating 3D animations of lizard displays, comparing response probabilities to the factorial combination of three motor patterns, three viewing angles and three distances. Results suggest that the tail-flick does not have a greater active space than other display motor patterns, but that each degrades predictably with distance, thereby providing potential ranging cues. In addition, display components are remarkably robust to variation in receiver orientation, so that efficacy should be maximized in most potential signalling situations. These findings are consistent with the hypothesis that duration is the principal determinant of signal efficacy in this system.
Publisher: Springer Science and Business Media LLC
Date: 25-11-2016
Publisher: The Royal Society
Date: 06-10-2010
Abstract: Animals are active at different times of the day and their activity schedules are shaped by competition, time-limited food resources and predators. Different temporal niches provide different light conditions, which affect the quality of visual information available to animals, in particular for navigation. We analysed caste-specific differences in compound eyes and ocelli in four congeneric sympatric species of Myrmecia ants, with emphasis on within-species adaptive flexibility and daily activity rhythms. Each caste has its own lifestyle: workers are exclusively pedestrian alate females lead a brief life on the wing before becoming pedestrian alate males lead a life exclusively on the wing. While workers of the four species range from diurnal, diurnal-crepuscular, crepuscular-nocturnal to nocturnal, the activity times of conspecific alates do not match in all cases. Even within a single species, we found eye area, facet numbers, facet sizes, rhabdom diameters and ocelli size to be tuned to the distinct temporal niche each caste occupies. We discuss these visual adaptations in relation to ambient light levels, visual tasks and mode of locomotion.
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: Cambridge University Press
Date: 24-06-2010
Publisher: Springer Science and Business Media LLC
Date: 16-08-2016
DOI: 10.1038/SREP31573
Abstract: Competition between animals for limited resources often involves signaling to establish ownership or dominance. In some species, the defended resource relates to suitable thermal conditions and refuge from predators. This is particularly true of burrow-dwelling lizards such as the Qinghai toad-headed agama ( Phrynocephalus vlangalii ), which are found on the Tibetan plateau of western China. Male and female lizards occupy separate burrows, which are vital for anti-predator behaviour during warmer months when lizards are active and, crucially, provide shelter from harsh winter conditions. These lizards are readily observed signaling by means of tail displays on the sand dunes they inhabit. Given the selective pressure to hold such a resource, both males and females should exhibit territorial behaviour and we considered this study system to examine in detail how social context influences motion based territorial signaling. We confirmed that territorial signaling was used by both sexes and by adopting a novel strategy that permitted 3D reconstruction of tail displays, we identified significant variation due to social context. However, signal structure was not related to lizard morphology. Clearly, the burrow is a highly valued resource and we suggest that additional variation in signaling behaviour might be mediated by resource quality.
Publisher: The Company of Biologists
Date: 12-2003
DOI: 10.1242/JEB.00664
Abstract: Many animal signals have introductory components that alert receivers. Ex les from the acoustic and visual domains show that this effect is often achieved with high intensity, a simple structure and a short duration. Quantitative analyses of the Jacky dragon Amphibolurus muricatusvisual display reveal a different design: the introductory tail-flick has a lower velocity than subsequent components of the signal, but a longer duration. Here, using a series of video playback experiments with a digitally animated tail, we identify the properties responsible for signal efficacy. We began by validating the use of the computer-generated tail, comparing the responses to digital video footage of a lizard tail-flick with those to a precisely matched 3-D animation (Experiment 1). We then examined the effects of variation in stimulus speed, acceleration, duration and period by expanding and compressing the time scale of the sequence (Experiment 2). The results identified several variables that might mediate recognition. Two follow-up studies assessed the importance of tail-flick litude (Experiment 3),movement speed and signal duration (Experiment 4). Lizard responses to this array of stimuli reveal that duration is the most important characteristic of the tail-flick, and that intermittent signalling has the same effect as continuous movement. We suggest that signal design may reflect a trade-off between efficacy and cost.
Publisher: The Royal Society
Date: 30-10-2008
Abstract: Animal signals are constrained by the environment in which they are transmitted and the sensory systems of receivers. Detection of movement-based signals is particularly challenging against the background of wind-blown plants. The Australian lizard Amphibolurus muricatus has recently been shown to compensate for greater plant motion by prolonging the introductory tail-flicking component of its movement-based display. Here I demonstrate that such modifications to signal structure are useful because environmental motion lengthens the time lizard receivers take to detect tail flicks. The spatio-temporal properties of animal signals and environmental motion are thus sufficiently similar to make signal detection more difficult. Environmental motion, therefore, must have had an influence on the evolution of movement-based signals and motion detection mechanisms.
Publisher: Elsevier BV
Date: 07-2020
Publisher: Elsevier BV
Date: 10-2016
Publisher: Elsevier BV
Date: 07-2002
Publisher: Elsevier BV
Date: 03-2006
DOI: 10.1016/J.BEPROC.2005.12.002
Abstract: In this study, we investigated the feasibility of applying neural networks to understanding movement-based visual signals. Networks based on three different models were constructed, varying in their input format and network architecture: a Static Input model, a Dynamic Input model and a Feedback model. The task for all networks was to distinguish a lizard (Amphibolurus muricatus) tail-flick from background plant movement. Networks based on all models were able to distinguish the two types of visual motion, and generalised successfully to unseen exemplars. We used curves defined by the receiver-operating characteristic (ROC) to select a single network from each model to be used in regression analyses of network response and several motion variables. Collectively, the models predicted that tail-flick efficacy would be enhanced by faster speeds, greater acceleration and longer durations.
Publisher: The Company of Biologists
Date: 08-2015
DOI: 10.1242/JEB.128967
Publisher: Elsevier BV
Date: 07-2016
Publisher: Frontiers Media SA
Date: 18-04-2019
Publisher: Informa UK Limited
Date: 09-2016
DOI: 10.1071/MU15095
Publisher: CSIRO Publishing
Date: 22-03-2022
DOI: 10.1071/ZO21047
Abstract: Communication signals underpin the social lives of animals, from species recognition to mate selection and territory defense. Animal signals are erse in structure between and within species, with the ersity reflecting interacting factors of shared evolutionary history, constraints imposed on senders and receivers and the ecological context in which signalling takes place. The dragon lizards of Australia (family Agamidae) are known for their movement-based visual displays and are useful models for how ecology influences behaviour. However, we know little about the communication strategies of many species. Our aim here was to provide new knowledge on some of these species, focusing on the north-west of Western Australia. We filmed within-species pairwise interactions of Diporiphora superba, D. bennetti, D. sobria and Ctenophorus isolepis isolepis. We describe and quantify for the first time push-up displays by D. superba and C. isolepis isolepis and tail waving displays of D. bennetti. Only D. sobria did not generate movement-based visual signals. We have confirmed that more species engage in such behaviour than previously reported, but further work is required to document the full repertoire of these species. The implications of our work are discussed in the context of signal structure, function and environmental context.
Publisher: Elsevier BV
Date: 2018
Publisher: Springer Science and Business Media LLC
Date: 06-2017
DOI: 10.1007/S00359-017-1185-5
Abstract: Signaling species occurring in sympatry are often exposed to similar environmental constraints, so similar adaptations to enhance signal efficacy are expected. However, potentially opposing selective pressures might be present to ensure species recognition. Here, we analyzed the movement-based signals of two pairs of sympatric lizard species to consider how reliable communication is maintained while avoiding misidentification. Our novel approach allows us to quantify signal contrast with plant motion noise at any site we measure, including those utilized by other species. Ctenophorus caudicinctus and Gowidon longirostris differed in display complexity and motor pattern use. They also differed in overall morphology, but their signal contrast scores are strikingly similar. These results demonstrate similar adaptations to their shared environment while maintaining species recognition cues. In contrast, Ctenophorus fordi and Ctenophorus pictus are much closer in appearance, but C. pictus produces considerably higher signal contrast scores, which we suggest is attributable to the absence of territoriality in C. fordi. Taken together, our data provide evidence for adaptation to the local environment in movement-based signals, while also meeting species recognition requirements, but the selective pressure to deal with local conditions is mediated by signal function.
Publisher: Springer Science and Business Media LLC
Date: 03-02-2022
DOI: 10.1007/S00359-022-01544-3
Abstract: Animals signals must be detected by receiver sensory systems, and overcome a variety of local ecological factors that could otherwise affect their transmission and reception. Habitat structure, competition, avoidance of unintended receivers and varying environmental conditions have all been shown to influence how animals signal. Environmental noise is also crucial, and animals modify their behavior in response to it. Animals generating movement-based visual signals have to contend with wind-blown plants that generate motion noise and can affect the detection of salient movements. The lizard Amphibolurus muricatus uses tail flicking at the start of displays to attract attention, and we hypothesized that tail movements are ideally suited to this function. We compared visual litudes generated by tail movements with push-ups, which are a key component of the rest of the display. We show that tail movement litudes are highly variable over the course of the display but consistently greater than litudes generated by push-ups and not constrained by viewing position. We suggest that these features, combined with the tail being a light structure that does not compromise other activities, provide an ideal introductory component for attracting attention in the ecological setting in which they are generated.
Publisher: Wiley
Date: 18-09-2016
DOI: 10.1111/AEC.12312
Publisher: Elsevier BV
Date: 05-2002
Publisher: The Royal Society
Date: 30-01-2007
Abstract: Extensive research over the last few decades has revealed that many acoustically communicating animals compensate for the masking effect of background noise by changing the structure of their signals. Familiar ex les include birds using acoustic properties that enhance the transmission of vocalizations in noisy habitats. Here, we show that the effects of background noise on communication signals are not limited to the acoustic modality, and that visual noise from windblown vegetation has an equally important influence on the production of dynamic visual displays. We found that two species of Puerto Rican lizard, Anolis cristatellus and A. gundlachi , increase the speed of body movements used in territorial signalling to apparently improve communication in visually ‘noisy’ environments of rapidly moving vegetation. This is the first evidence that animals change how they produce dynamic visual signals when communicating in noisy motion habitats. Taken together with previous work on acoustic communication, our results show that animals with very different sensory ecologies can face similar environmental constraints and adopt remarkably similar strategies to overcome these constraints.
Publisher: Springer Science and Business Media LLC
Date: 30-06-2015
Publisher: The Royal Society
Date: 11-2016
Abstract: The hormone fluctuations that an animal experiences during ovulation can have lifelong effects on developing offspring. These hormones may act as an adaptive mechanism, allowing offspring to be ‘pre-programmed’ to survive in an unstable environment. Here, we used a transgenerational approach to examine the effects of elevated maternal corticosterone (CORT) on the future reproductive success of female offspring. We show that female zebra finches ( Taeniopygia guttata ) exposed to embryonic CORT produce daughters that have equal reproductive success (clutch sizes, fertility, hatching success) compared with the daughters produced from untreated mothers, but their offspring had accelerated post-hatching growth rates and were significantly heavier by nutritional independence. Although there was no significant effect on primary offspring sex ratio, females from CORT-treated mothers produced significantly female-biased clutches by nutritional independence. To the best of our knowledge, this is the first record of a transgenerational sex ratio bias in response to elevated maternal CORT in any avian species.
Publisher: Elsevier BV
Date: 08-2015
Publisher: The Company of Biologists
Date: 2015
DOI: 10.1242/JEB.120808
Abstract: Insects have evolved morphological and physiological adaptations in response to selection pressures inherent to their ecology. Consequently, visual performances and acuity often significantly vary between different insect species. Whilst psychophysics has allowed for the accurate determination of visual acuity for some Lepidoptera and Hymenoptera, very little is known about other insect taxa that cannot be trained to positively respond to a given stimulus. In this study, we demonstrate that prior knowledge of insect colour preferences can be used to facilitate acuity testing. We focus on four psyllid species (Hemiptera: Psylloidea: Aphalaridae), namely Ctenarytaina eucalypti, C. bipartita, Anoeconeossa bundoorensis and Glycaspis brimblecombei, that differ in their colour preferences and utilization of different host-plant modules (e.g. apical buds, stems, leaf lamellae) and test their visual acuity in a modified Y-maze adapted to suit psyllid searching behaviour. Our study reveals that psyllids have visual acuity ranging from 6.3° to 8.7°. Morphological measurements for different species revealed a close match between inter-ommatidial angles and behaviourally determined visual angles (between 5.5°and 6.6°) suggesting detection of colour stimuli at the single ommatidium level. Whilst our data support isometric scaling of psyllids eyes for C. eucalypti, C. bipartita and G. brimblecombei, a morphological trade-off between light sensitivity and spatial resolution was found in A. bundoorensis. Overall, species whose microhabitat preferences require more movement between modules appear to possess superior visual acuities. The psyllid searching behaviours that we describe with the help of tracking software depict species-specific strategies presumably evolved to optimize searching for food and oviposition sites.
Publisher: Elsevier BV
Date: 09-2006
Publisher: Wiley
Date: 10-10-2015
DOI: 10.1111/AEC.12195
Publisher: Wiley
Date: 07-2008
Publisher: Proceedings of the National Academy of Sciences
Date: 08-04-2013
Abstract: Compelling evidence from many animal taxa indicates that male genitalia are often under postcopulatory sexual selection for characteristics that increase a male’s relative fertilization success. There could, however, also be direct precopulatory female mate choice based on male genital traits. Before clothing, the nonretractable human penis would have been conspicuous to potential mates. This observation has generated suggestions that human penis size partly evolved because of female choice. Here we show, based upon female assessment of digitally projected life-size, computer-generated images, that penis size interacts with body shape and height to determine male sexual attractiveness. Positive linear selection was detected for penis size, but the marginal increase in attractiveness eventually declined with greater penis size (i.e., quadratic selection). Penis size had a stronger effect on attractiveness in taller men than in shorter men. There was a similar increase in the positive effect of penis size on attractiveness with a more masculine body shape (i.e., greater shoulder-to-hip ratio). Surprisingly, larger penis size and greater height had almost equivalent positive effects on male attractiveness. Our results support the hypothesis that female mate choice could have driven the evolution of larger penises in humans. More broadly, our results show that precopulatory sexual selection can play a role in the evolution of genital traits.
Publisher: Springer Science and Business Media LLC
Date: 06-2003
DOI: 10.1007/S00359-003-0423-1
Abstract: Visual systems are typically selective in their response to movement. This attribute facilitates the identification of functionally important motion events. Here we show that the complex push-up display produced by male Jacky dragons ( Amphibolurus muricatus) is likely to have been shaped by an interaction between typical signalling conditions and the sensory properties of receivers. We use novel techniques to define the structure of the signal and of a range of typical moving backgrounds in terms of direction, speed, acceleration and sweep area. Results allow us to estimate the relative conspicuousness of each motor pattern in the stereotyped sequence of which displays are composed. The introductory tail-flick sweeps a large region of the visual field, is sustained for much longer than other components, and has velocity characteristics that ensure it will not be filtered in the same way as wind-blown vegetation. These findings are consistent with the idea that the tail-flick has an alerting function. Quantitative analyses of movement-based signals can hence provide insights into sensory processes, which should facilitate identification of the selective forces responsible for structure. Results will complement the detailed models now available to account for the design of static visual signals.
Publisher: Wiley
Date: 06-11-2018
Publisher: Elsevier BV
Date: 11-2018
Publisher: American Psychological Association (APA)
Date: 09-1999
Publisher: Elsevier BV
Date: 04-2017
Publisher: Wiley
Date: 09-2018
DOI: 10.1111/JAV.01752
Publisher: Springer Science and Business Media LLC
Date: 11-07-2017
Start Date: 2015
End Date: 2016
Funder: National Geographic Society
View Funded ActivityStart Date: 2005
End Date: 2007
Funder: Australian Research Council
View Funded ActivityStart Date: 2017
End Date: 2019
Funder: Australian Research Council
View Funded ActivityStart Date: 2016
End Date: 2019
Funder: National Natural Science Foundation of China
View Funded ActivityStart Date: 2003
End Date: 2005
Funder: Australian Research Council
View Funded ActivityStart Date: 04-2005
End Date: 12-2008
Amount: $250,000.00
Funder: Australian Research Council
View Funded ActivityStart Date: 2017
End Date: 12-2022
Amount: $333,339.00
Funder: Australian Research Council
View Funded ActivityStart Date: 02-2003
End Date: 12-2005
Amount: $270,000.00
Funder: Australian Research Council
View Funded Activity