Biology subjects

Ward, A. J. W.

Publications and source records attributed to Ward, A. J. W..

3 recordsLinked to original sources

bioRxiv2022

Investigating manta ray collective movements via drone surveys

Detailed observational research on free-ranging species of marine megafauna is required to understand their behavioural ecology, including how groups respond to environmental and anthropogenic pressures. New technologies are opening up potential for research on these species in the wild, especially on group-based and collective behaviours. Reef manta rays (Mobula alfredi) are socially interactive elasmobranchs that form groups in coastal reef habitats. Collective behaviours are likely important to their fitness, but may be disturbed by humans. Using small, remotely-piloted drones, we performed aerial observations of manta ray groups in Raja Ampat, West Papua. We empirically quantified patterns of collective movement including relative spatial positions, alignment, speed and leadership positions of conspecifics. We found unique patterns of spatial positioning, alignment and leadership, including differences between sexes, and high levels of local attraction, which were suggestive of distinct collective behaviour states. We suggest that rules of interaction in manta rays vary at the individual level and can shift depending on local environmental and social conditions. Leader-follower behaviour likely has broad importance to cohesive movement and social behaviour in M. alfredi. We suggest that further studies on manta ray movement should consider utilising models of collective motion that capture group-level behavioural processes.

animal behavior and cognition↗

bioRxiv2021

Changes in movement characteristics in response to private and social information acquisition of socially foraging fish

To overcome the cost of competition resulting from foraging in a group, individuals may balance their use of private (i.e., acquired from personal sampling) and social (i.e., acquired by watching other individuals) information to adjust their foraging strategy accordingly. Reliability of private information about environmental characteristics, such as the spatial distribution of prey, is thus likely to affect individual movement and social interactions during foraging. Our aim was to investigate how movement characteristics of foraging individuals changed as they acquired reliable private information about the spatial occurrence of prey in a foraging context. We allowed guppies (Poecilia reticulata) to develop the reliability of their private knowledge about prey spatial occurrence by repeatedly testing shoals in a foraging task under three experimental distributions of prey: 1) aggregated prey forming three patches located in fixed locations, 2) scattered distribution of prey with random locations, or 3) no prey (used as control). We then applied tracking methods to obtain individual time series of spatial coordinates from which we computed a suite of movement variables reflecting search effort, social proximity and locomotion characteristics during foraging, to examine changes occurring over repeated trials and to investigate which best explained foraging success. We show that foraging shoals became more efficient at finding and consuming food over the first three days by increasing their time spent active. Over time, individuals foraging on either scattered or aggregated prey travelled greater distances, showed an increasing distance to their closest neighbour and became slightly more stochastic in their acceleration profile, compared to control individuals. We found that behaviour changed as private information increased over time, with a clear behavioural shift occurring on the third testing day. Social proximity was the major predictor of foraging success in the absence of prior foraging information, while search effort became the most important predictors of foraging success as information increased. In conclusion, we show that individual movement patterns changed as they acquired private information. Contrary to our predictions, the spatial distribution of prey did not affect any of the movement variables of interest. Our results emphasise the importance of information in shaping movement behaviour in animals.

animal behavior and cognition↗

bioRxiv2021

Self-organization and information transfer in Antarctic krill swarms

Antarctic krill swarms are one of the largest known animal aggregations. However, despite being the keystone species of the Southern Ocean, little is known about how swarms are formed and maintained, and we lack a detailed understanding of the local interactions between individuals that provide the basis for these swarms. Here we analyzed the trajectories of captive, wild-caught krill in 3D to determine individual level interaction rules and quantify patterns of information flow. Our results suggest krill operate a novel form of collective organization, with measures of information flow and individual movement adjustments expressed most strongly in the vertical dimension, a finding not seen in other swarming species. In addition, local directional alignment with near neighbors, and strong regulation of both direction and speed relative to the positions of groupmates suggest social factors are vital to the formation and maintenance of swarms. This research represents a first step in understanding the fundamentally important swarming behavior of krill.

animal behavior and cognition↗