Does detection range matter for inferring social networks in a benthic shark using acoustic telemetry?

Accurately estimating contacts between animals can be critical in ecological studies such as examining social structure, predator–prey interactions or transmission of information and disease. While biotelemetry has been used successfully for such studies in terrestrial systems, it is still under development in the aquatic environment. Acoustic telemetry represents an attractive tool to investigate spatio-temporal behaviour of marine fish and has recently been suggested for monitoring underwater animal interactions. To evaluate the effectiveness of acoustic telemetry in recording interindividual contacts, we compared co-occurrence matrices deduced from three types of acoustic receivers varying in detection range in a benthic shark species. Our results demonstrate that (i) associations produced by acoustic receivers with a large detection range (i.e. Vemco VR2W) were significantly different from those produced by receivers with smaller ranges (i.e. Sonotronics miniSUR receivers and proximity loggers) and (ii) the position of individuals within their network, or centrality, also differed. These findings suggest that acoustic receivers with a large detection range may not be the best option to represent true social networks in the case of a benthic marine animal. While acoustic receivers are increasingly used by marine ecologists, we recommend users first evaluate the influence of detection range to depict accurate individual interactions before using these receivers for social or predator–prey studies. We also advocate for combining multiple receiver types depending on the ecological question being asked and the development of multi-sensor tags or testing of new automated proximity loggers, such as the Encounternet system, to improve the precision and accuracy of social and predator–prey interaction studies

Isolation rearing does not constrain social plasticity in a family-living lizard

Financial support for this research was provided by the Australian Research Council (ARC DP130102998, grant to MJW and RWB), Natural Sciences and Engineering Research Council of Canada (scholarship to JLR), the Australasian Society for the Study of Animal Behavior, the Australian Museum, and Macquarie University (scholarship to JLR). DWAN was supported by an ARC Discovery Early Career Research Award (DE150101774) and University of New South Wales Vice Chancellors Fellowship.An animal’s social environment can be both dynamic and complex. Thus, social species often garner fitness benefits through being plastic in their social behavior. Yet, social plasticity can be constrained by an individual’s experience. We examined the influence of early social environment on social behavior in the tree skink (Egernia striolata), a family-living lizard. In the first phase of this study, we reared juveniles in 2 different social environments for 1.5 years: either in isolation or in unrelated pairs. We quantified each lizard’s sociability at 4-month intervals using a standardized laboratory assay and found that isolated lizards were more sociable, spending the assay closer to an adult female, than socially-reared lizards. In the second phase of this study (at the end of 1.5 years), we released all lizards into a semi-natural environment, observed their associations, and used social network analysis to quantify social behavior. During the initial 6 weeks post-release, we detected no differences in social behavior between rearing treatments. However, during the following 6 months differences emerged. Isolated lizards were more homogeneous in the strength of their associations than socially-reared lizards. Also, at first, isolated lizards associated more strongly than socially-reared lizards. Over time, isolated lizard associations became weaker and involved fewer lizards. In contrast, the level and number of associations of socially-reared lizards were stable over time. Our findings suggest that early experience influences tree skink social behavior but does not constrain social plasticity: isolation rearing did not limit their ability to respond to a novel social environment.PostprintPeer reviewe

Diving into the vertical dimension of elasmobranch movement ecology

Knowledge of the three-dimensional movement patterns of elasmobranchs is vital to understand their ecological roles and exposure to anthropogenic pressures. To date, comparative studies among species at global scales have mostly focused on horizontal movements. Our study addresses the knowledge gap of vertical movements by compiling the first global synthesis of vertical habitat use by elasmobranchs from data obtained by deployment of 989 biotelemetry tags on 38 elasmobranch species. Elasmobranchs displayed high intra- and interspecific variability in vertical movement patterns. Substantial vertical overlap was observed for many epipelagic elasmobranchs, indicating an increased likelihood to display spatial overlap, biologically interact, and share similar risk to anthropogenic threats that vary on a vertical gradient. We highlight the critical next steps toward incorporating vertical movement into global management and monitoring strategies for elasmobranchs, emphasizing the need to address geographic and taxonomic biases in deployments and to concurrently consider both horizontal and vertical movements

Diving into the vertical dimension of elasmobranch movement ecology

Knowledge of the three-dimensional movement patterns of elasmobranchs is vital to understand their ecological roles and exposure to anthropogenic pressures. To date, comparative studies among species at global scales have mostly focused on horizontal movements. Our study addresses the knowledge gap of vertical movements by compiling the first global synthesis of vertical habitat use by elasmobranchs from data obtained by deployment of 989 biotelemetry tags on 38 elasmobranch species. Elasmobranchs displayed high intra- and interspecific variability in vertical movement patterns. Substantial vertical overlap was observed for many epipelagic elasmobranchs, indicating an increased likelihood to display spatial overlap, biologically interact, and share similar risk to anthropogenic threats that vary on a vertical gradient. We highlight the critical next steps toward incorporating vertical movement into global management and monitoring strategies for elasmobranchs, emphasizing the need to address geographic and taxonomic biases in deployments and to concurrently consider both horizontal and vertical movements

Diving into the vertical dimension of elasmobranch movement ecology

Knowledge of the three-dimensional movement patterns of elasmobranchs is vital to understand their ecological roles and exposure to anthropogenic pressures. To date, comparative studies among species at global scales have mostly focused on horizontal movements. Our study addresses the knowledge gap of vertical movements by compiling the first global synthesis of vertical habitat use by elasmobranchs from data obtained by deployment of 989 biotelemetry tags on 38 elasmobranch species. Elasmobranchs displayed high intra- and interspecific variability in vertical movement patterns. Substantial vertical overlap was observed for many epipelagic elasmobranchs, indicating an increased likelihood to display spatial overlap, biologically interact, and share similar risk to anthropogenic threats that vary on a vertical gradient. We highlight the critical next steps toward incorporating vertical movement into global management and monitoring strategies for elasmobranchs, emphasizing the need to address geographic and taxonomic biases in deployments and to concurrently consider both horizontal and vertical movements

Structure of social networks and genetic diversity

47 page(s

Data from: Direct genetic evidence for reproductive philopatry and associated fine-scale migrations in female blacktip reef sharks (Carcharhinus melanopterus) in French Polynesia.

Conservation of top predators has been emphasised as essential in an ecosystem due to their role in trophic chain regulation. Optimization of conservation strategies for these endangered marine top predators requires direct estimates of breeding patterns and connectivity, which are essential to understand their population dynamics. While there have been some attempts to investigate breeding patterns of reef sharks from litter reconstruction using molecular analyses, direct fine-scale migrations of female sharks for parturition as well as connectivity at a medium scale, such as between islands, remain mostly unknown. We used microsatellite DNA markers and a likelihood-based parentage analysis to determine breeding patterns of female blacktip reef sharks in Moorea (Society Islands, French Polynesia). Such an approach demonstrates that while most females gave birth at their home island, some migrated to specific nursery areas outside their home range, sometimes going to another island (up to 50 km across deep ocean). Analysis also revealed that females migrated to the same nursery on every birthing event. Many offspring showed a high level of inbreeding indicating an overall reduced population size, restricted movements and dispersal, or specific mating behaviour. Females represent the vectors that transport the genes at nursery grounds, and their fidelity should thus define reproductive units. As females seem to be philopatric, males could be the ones dispersing genes between metapopulations. These results highlight the need for conservation of coastal zones where female reef sharks seems to exhibit philopatry during the breeding season

Direct genetic evidence for reproductive philopatry and associated fine-scale migrations in female blacktip reef sharks (Carcharhinus melanopterus) in French Polynesia

Conservation of top predators has been emphasized as essential in an ecosystem due to their role in trophic chain regulation. Optimizing conservation strategies for these endangered marine top predators requires direct estimates of breeding patterns and connectivity as these are essential to understanding the population dynamics. There have been some attempts to investigate breeding patterns of reef sharks from litter reconstruction using molecular analyses. However, direct fine-scale migrations of female sharks for parturition as well as connectivity at a medium scale like between islands remain mostly unknown. We used microsatellite DNA markers and a likelihood-based parentage analysis to determine breeding patterns of female blacktip reef sharks in Moorea (Society Islands, French Polynesia). Most females gave birth at their home island but some migrated to specific nursery areas outside the area they are attached to, sometimes going to another island 50 km away across deep ocean. Our analysis also revealed that females migrated to the same nursery for every birthing event. Many offspring showed a high level of inbreeding indicating an overall reduced population size, restricted movements and dispersal, or specific mating behaviour. Females represent the vectors that transport the genes at nursery grounds, and their fidelity should thus define reproductive units. As females seem to be philopatric, males could be the ones dispersing genes between populations. These results highlight the need to conserve coastal zones where female reef sharks seem to exhibit philopatry during the breeding season.14 page(s

Social Networks in fish

23 page(s

Sharks and rays of the Austral Islands , emblematic species conservation

8 page(s