Quorum decision making coordinates group departure decisions in Eurasian oystercatchers, Haematopus ostralegus

Prey species that form groups gain a range of benefits from associating with conspecifics, including access to social information. Groups typically coordinate collective movement through local interactions, where individuals copy their nearest neighbours' behaviour to generate group level decisions. However, individuals in a group may not always make ‘correct’ decisions, and blind copying of behaviour can lead to the spread of poor information and maladaptive cascades. To impede the spread of poor information, many animals that form groups have developed information-dampening mechanisms such as consensus decision making through the quorum response. In this study we monitored flocks of roosting Eurasian oystercatchers with a view to understanding the mechanics of group departure decisions and to test for the presence of a quorum response. Nearing high tide, oystercatchers would leave the roosting site en masse, where the timing of departure of many individuals was coordinated. Coordinating the timing of mass departures was a complex task as single birds and small groups frequently joined and departed from the roosting site, meaning individuals had to decide which departures to copy and which to ignore. Individual oystercatchers were more likely to depart within 10s of another bird if they were closer together in the group, suggesting that departure information may be transferred locally between neighbouring birds. While single departures were very common, most individuals departed in groups of 10 or more, showing that single departures were a relatively weak departure cue and were frequently ignored by the rest of the group. The probability of an individual joining a departure event was higher with increasing departure group size in a nonlinear (sigmoidal) relationship. This trend is consistent with a quorum response with the propensity to copy the departure of groupmates sharply increasing at a quorum threshold of about 10 birds.Publisher PDFPeer reviewe

Three-spined sticklebacks show dimension-specific preferences for shelter

Funding Information: We are grateful to the Association for the Study of Animal Behaviour (ASAB) for funding this work through an ASAB research grant to N.A.R.J. Thank you also to the University of St Andrews Research internship Scheme (StARIS) which provided funding for G.G.Shelter is an important resource, serving as protection from rivals, predators and environmental stressors. The physical dimensions of a potential shelter are an important factor that can affect decisions about potential shelter options. Animals must select a shelter that they can fit into and use as a refuge, but beyond that, do they show fine-scale preferences based on shelter dimensions? This question has been actively studied for species whose shelter use is closely connected to their life cycles, such as obligate shell dwellers and nest-inhabiting species. However, preferences and decision making for temporary shelters has received less attention. We tested whether three-spined sticklebacks, Gasterosteus aculeatus, a common laboratory model, exhibit preferences in shelter use (actively entering and spending time within a shelter) between shelters with different dimensions. We used PVC tubes of different dimensions as shelters and conducted a simultaneous choice assay where individual fish were presented with each of three tubes available for use as shelter. The fish showed a clear preference, using larger diameter shelters more frequently than either of the other two options. There was no difference in the number of nonsheltering visits fish made or time to enter a shelter across tube sizes, which suggests an active selection by the fish rather than passive bias. There was no difference in duration of time spent within a shelter, suggesting that despite these preferences, actual benefit derived by the fish may be decoupled from the shelter dimensions. Our results offer opportunities for future research that addresses longer term questions in both behavioural ecology and welfare. What drives the preference for larger diameter tubes, and are there are long-term benefits to shelter with preferred dimensions? Certainly, our results suggest that housing sticklebacks with larger diameter shelters may be a simple and convenient means to improve welfare.Publisher PDFPeer reviewe

Fish pool their experience to solve problems collectively

This work was funded by an ERC Advanced grant to KNL (EVOCULTURE, Ref: 232823)Access to information is a key advantage of grouping. Although experienced animals can lead others to solve problems, less is known about whether partially informed individuals can pool experiences to overcome challenges collectively. Here we provide evidence of such ‘experience-pooling’. We presented shoals of sticklebacks (Gasterosteus aculeatus) with a two-stage foraging task requiring them to find and access hidden food. Individual fish were either inexperienced or had knowledge of just one of the stages. Shoals containing individuals trained in each of the stages pooled their expertise, allowing more fish to access the food, and to do so more rapidly, compared with other shoal compositions. Strong social effects were identified: the presence of experienced individuals increased the likelihood of untrained fish completing each stage. These findings demonstrate that animal groups can integrate individual experience to solve multi-stage problems, and have implications for our understanding of social foraging, migration and social systems.PostprintPeer reviewe

On closer inspection : reviewing the debate on whether fish cooperate to inspect predators

This work was funded by an EASTBIO DTP scholarship to A. Li Veiros.Cooperative behaviours, which benefit a recipient, are widespread in the animal kingdom; yet their evolution is not straightforward. Reciprocity, i.e., cooperating with previously experienced cooperative partners, has been suggested to underly cooperation, but has been contested throughout the years. Once a textbook example of reciprocity was cooperative predator inspection, where one or several individuals leave their group to approach a potential threat. Each can at any point stop or retreat, increasing the risk for its partner. It was suggested that inspecting individuals follow a specific reciprocal strategy called tit-for-tat, i.e., cooperating on the first move and then copying the partner's last move. Numerous studies provide evidence to support the claim that fish cooperate to inspect predators, including three-spined sticklebacks (Gasterosteus aculeatus), guppies (Poecilia reticulata) and minnows (Phoxinus phoxinus). However, over the past few decades some scholars have expressed scepticism whether predator inspection is indeed a cooperative behaviour or rather a case of by-product mutualism, which describes behaviours that benefit a partner as a corollary of an otherwise selfish behaviour. For instance, it has been shown that pairs of fish moving in unfamiliar environments appear to coordinate movements even in the absence of predators. Many studies have also used coarse measures of overall approach rates towards predators rather than the fine-grained analyses necessary to infer tit-for-tat in cooperative inspections. Now is the time to return to the question of cooperative predator inspection with new tools and approaches to resolve a decades-old debate.Publisher PDFPeer reviewe

Physical enrichment research for captive fish : time to focus on the DETAILS

Funding: Fisheries Society of the British Isles (GB) (Grant Number(s): PhD Studentship).Growing research effort has shown that physical enrichment (PE) can improve fish welfare and research validity. However, the inclusion of PE does not always result in positive effects and conflicting findings have highlighted the many nuances involved. Effects are known to depend on species and life stage tested, but effects may also vary with differences in the specific items used as enrichment between and within studies. Reporting fine-scale characteristics of items used as enrichment in studies may help to reveal these factors. We conducted a survey of PE-focused studies published in the last 5 years to examine the current state of methodological reporting. The survey results suggest that some aspects of enrichment are not adequately detailed. For example, the amount and dimensions of objects used as enrichment were frequently omitted. Similarly, the ecological relevance, or other justification, for enrichment items was frequently not made explicit. Focusing on ecologically relevant aspects of PE and increasing the level of detail reported in studies may benefit future work and we propose a framework with the acronym DETAILS ( D imensions, E cological rationale, T iming of enrichment, A mount, I nputs, L ighting and S ocial environment). We outline the potential importance of each of the elements of this framework with the hope it may aid in the level of reporting and standardization across studies, ultimately aiding the search for more beneficial types of PE and the development of our understanding and ability to improve the welfare of captive fish and promote more biologically relevant behaviour.Publisher PDFPeer reviewe

Reply to Jolles (2018) : comment on ‘Consistency of fish-shoal social network structure under laboratory conditions (Gaffney & Webster, 2018)’

In a paper this year (Gaffney and Webster 2018) we presented a series of experiments in which we investigated the effects of arena size and inter-observation duration upon basic social network structure metrics and related measures for shoals of threespine sticklebacks Gasterosteus aculeatus L. 1758.PostprintPeer reviewe

Teaching laboratory for large cohorts of undergraduates : private and social information in fish

A challenge in the Bachelor's studies in Biology is to strike a balance between reducing the teaching of practical scientific experiments to what is feasible in a short time, and teaching “real” science in undergraduate laboratories for high numbers of participants. We describe a laboratory in behavioral biology, with the primary focus on the student learning. However, also the underlying scientific question and the results of the experiment, namely the behavior of the three‐spined stickleback (Gasterosteus aculeatus) in a trade‐off situation during foraging, is without a doubt timely and sufficient for scientific studies on this subject, and this through the experiments conducted and data collected by the students. The students rated this laboratory well and learned at the end that social information is certainly important, but that self‐learning can be more important, and this not only in small fish, but also for the students themselves.Publisher PDFPeer reviewe

Local interactions and global properties of wild, free-ranging stickleback shoals

Funding: Australian Research Council. A.J.W.W. and T.M.S. were supported by a Discovery Project Grant from the Australian Research Council. D.J.T.S. and J.E.H.-R. were supported by a Knut & Alice Wallenberg Foundation Grant.Collective motion describes the global properties of moving groups of animals and the self-organized, coordinated patterns of individual behaviour that produce them. We examined the group-level patterns and local interactions between individuals in wild, free-ranging shoals of three-spine sticklebacks, Gasterosteus aculeatus. Our data reveal that the highest frequencies of near-neighbour encounters occur at between one and two body lengths from a focal fish, with the peak frequency alongside a focal individual. Fish also show the highest alignment with these laterally placed individuals, and generally with animals in front of themselves. Furthermore, fish are more closely matched in size, speed and orientation to their near neighbours than to more distant neighbours, indicating local organization within groups. Among the group level properties reported here, we find that polarization is strongly influenced by group speed, but also the variation in speed among individuals and the nearest neighbour distances of group members. While we find no relationship between group order and group size, we do find that larger groups tend to have lower nearest neighbour distances, which in turn may be important in maintaining group order.Publisher PDFPeer reviewe

No experimental evidence of stress-induced hyperthermia in zebrafish (Danio rerio)

NJ was supported by a studentship from The Fisheries Society of The British Isles.Stress-induced hyperthermia (SIH) is characterised by a rise in body temperature in response to a stressor. In endotherms SIH is mediated by the autonomic nervous system, whereas ectotherms must raise their body temperature via behavioural means by moving to warmer areas within their environment (behavioural thermoregulation). A recent study suggested that zebrafish (Danio rerio), an important model species, may move to warmer water in response to handling and confinement and thus exhibit SIH, which, if accepted, may have important practical and welfare implications. However an alternative hypothesis proposed that the observed movements may been produced by avoidance behaviour rather than behavioural thermoregulation. Investigating the claims for SIH in zebrafish further we conducted two experiments that extend the earlier study. The first experiment incorporated new conditions that considered fish behaviour in the absence of thermal variation, i.e. their null distribution, an important condition that was not performed in the original study. The second was a refined version of the experiment to reduce the numbers of fish and aid movement between areas for the fish. In contrast to the previous study, we saw no effect of handling or confinement on preference for warmer areas, and no evidence for SIH in either experiment. Instead we observed a short-lived reduction in preference for warmer areas immediately post stress. Our work suggests that zebrafish may not experience SIH and claims regarding fish consciousness based on SIH may need to be revised.PostprintPeer reviewe

Short-range hunters: exploring the function and constraints of water shooting in dwarf gouramis

Ballistic predation is a rare foraging adaptation: in fishes, most attention has focused on a single genus, the archerfish, known to manipulate water to shoot down prey above the water surface. However, several gourami species also exhibit apparently similar ‘shooting’ behaviour, spitting water up to 5 cm above the surface. In a series of experiments, we explored the shooting behaviour and aspects of its significance as a foraging ability in the dwarf gourami (Trichogaster lalius). We investigated sex differences in shooting abilities to determine whether gourami shooting is related to the sex-specific bubble nest manufacture where males mix air and water at the surface to form bubbles. We found that, actually, both sexes were equally able to shoot and could learn to shoot a novel target. In a second experiment, we presented untrained gouramis with opportunities to shoot at live prey and found they successfully shot down both fruit flies and crickets. Finally, we explored the effect of target height on shooting performance to establish potential constraints of shooting as a foraging ability. The frequency of attempted shots and success of hitting targets decreased with height, whereas latency to shoot increased. We also observed that repeatable individual differences account for variation in these measures of shooting performance. Together, our results provide evidence that gourami shooting has a foraging function analogous to that of archerfish. Gourami shooting may serve as an example of convergent evolution and provide opportunities for comparative studies into the, as yet unexplored, ecology and evolution of shooting in fishes.Peer reviewe