Aggressive Signal Design in the Jacky Dragon (Amphibolurus muricatus): Display Duration Affects Efficiency

Computer-animated stimuli to measure motion sensitivity: constraints on signal design in the Jacky dragon

Identifying perceptual thresholds is critical for understanding the mechanisms that underlie signal evolution. Using computer-animated stimuli, we examined visual speed sensitivity in the Jacky dragon Amphibolurus muricatus, a species that makes extensive use of rapid motor patterns in social communication. First, focal lizards were tested in discrimination trials using random-dot kinematograms displaying combinations of speed, coherence, and direction. Second, we measured subject lizards’ ability to predict the appearance of a secondary reinforcer (1 of 3 different computer-generated animations of invertebrates: cricket, spider, and mite) based on the direction of movement of a field of drifting dots by following a set of behavioural responses (e.g., orienting response, latency to respond) to our virtual stimuli. We found an effect of both speed and coherence, as well as an interaction between these 2 factors on the perception of moving stimuli. Overall, our results showed that Jacky dragons have acute sensitivity to high speeds. We then employed an optic flow analysis to match the performance to ecologically relevant motion. Our results suggest that the Jacky dragon visual system may have been shaped to detect fast motion. This pre-existing sensitivity may have constrained the evolution of conspecific displays. In contrast, Jacky dragons may have difficulty in detecting the movement of ambush predators, such as snakes and of some invertebrate prey. Our study also demonstrates the potential of the computer-animated stimuli technique for conducting nonintrusive tests to explore motion range and sensitivity in a visually mediated species.

Technical and conceptual considerations for using animated stimuli in studies of animal behavior

Rapid technical advances in the field of computer animation (CA) and virtual reality (VR) have opened new avenues in animal behavior research. Animated stimuli are powerful tools as they offer standardization, repeatability, and complete control over the stimulus presented, thereby "reducing" and "replacing" the animals used, and "refining" the experimental design in line with the 3Rs. However, appropriate use of these technologies raises conceptual and technical questions. In this review, we offer guidelines for common technical and conceptual considerations related to the use of animated stimuli in animal behavior research. Following the steps required to create an animated stimulus, we discuss (I) the creation, (II) the presentation, and (III) the validation of CAs and VRs. Although our review is geared toward computer-graphically designed stimuli, considerations on presentation and validation also apply to video playbacks. CA and VR allow both new behavioral questions to be addressed and existing questions to be addressed in new ways, thus we expect a rich future for these methods in both ultimate and proximate studies of animal behavior.

Gestural communication in a new world parrot

Male birds can use visual signals to provide information about their sexual status, via bright coloration, sophisticated sexual displays and elaborate tail and head crests. The majority of forest bird species use vocal communication as their main strategy to show their physiological status during breeding season. It is also used to keep contact between individuals in the same group, in agonistic contexts, and by chicks begging for food. We registered, for the very first time, gestural communication acting in the context of biparental care for the Orange-winged Amazon, Amazona amazonica. This parrot presents at least nine different sounds uttered in contexts of alarm, agonistic, foraging, contact flight and others. This finding suggests that despite being a vocal species, this parrot can perform gestural communication related to parental care. The gestures exhibited by this species represent a strategy for survival, a clever way to protect the nest, reducing the risk of attracting the attention of predators.