62 research outputs found
Shark personalities? Repeatability of social network traits in a widely distributed predatory fish
No full textInterest in animal personalities has generated a burgeoning literature on repeatability in individual traits such as boldness or exploration through time or across different contexts. Yet, repeatability can be influenced by the interactive social strategies of individuals, for example, consistent inter-individual variation in aggression is well documented. Previous work has largely focused on the social aspects of repeatability in animal behaviour by testing individuals in dyadic pairings. Under natural conditions, individuals interact in a heterogeneous polyadic network. However, the extent to which there is repeatability of social traits at this higher order network level remains unknown. Here, we provide the first empirical evidence of consistent and repeatable animal social networks. Using a model species of shark, a taxonomic group in which repeatability in behaviour has yet to be described, we repeatedly quantified the social networks of ten independent shark groups across different habitats, testing repeatability in individual network position under changing environments. To understand better the mechanisms behind repeatable social behaviour, we also explored the coupling between individual preferences for specific group sizes and social network position. We quantify repeatability in sharks by demonstrating that despite changes in aggregation measured at the group level, the social network position of individuals is consistent across treatments. Group size preferences were found to influence the social network position of individuals in small groups but less so for larger groups suggesting network structure, and thus, repeatability was driven by social preference over aggregation tendency
Environmental DNA (eDNA) for monitoring marine mammals: Challenges and opportunities
No full textMonitoring marine mammal populations is essential to permit assessment of
population status as required by both national and international legislation.
Traditional monitoring methods often rely on visual and/or acoustic detections
from vessels and aircraft, but limitations including cost, errors in the detection
of some species and dependence on taxonomic expertise, as well as good
weather and visibility conditions often limit the temporal and spatial scale of
effective, long-term monitoring programs. In recent years, environmental DNA
(eDNA) has emerged as a revolutionary tool for cost-effective, sensitive, noninvasive
species monitoring in both terrestrial and aquatic realms. eDNA is a
rapidly developing field and a growing number of studies have successfully
implemented this approach for the detection and identification of marine
mammals. Here, we review 21 studies published between 2012 and 2021 that
employed eDNA for marine mammal monitoring including single species
detection, biodiversity assessment and genetic characterization. eDNA has
successfully been used to infer species presence (especially useful for rare,
elusive or threatened species) and to characterize the population genetic
structure, although additional research is needed to support the
interpretation of non-detections. Finally, we discuss the challenges and the
opportunities that eDNA could bring to marine mammal monitoring as a
complementary tool to support visual and acoustic methods
Inferring animal social networks and leadership: applications for passive monitoring arrays
No full textAnalyses of animal social networks have frequently benefited from techniques derived from other disciplines. Recently, machine learning algorithms have been adopted to infer social associations from time-series data gathered using remote, telemetry systems situated at provisioning sites. We adapt and modify existing inference methods to reveal the underlying social structure of wide-ranging marine predators moving through spatial arrays of passive acoustic receivers. From six months of tracking data for grey reef sharks (Carcharhinus amblyrhynchos) at Palmyra atoll in the Pacific Ocean, we demonstrate that some individuals emerge as leaders within the population and that this behavioural coordination is predicted by both sex and the duration of co-occurrences between conspecifics. In doing so, we provide the first evidence of long-term, spatially extensive social processes in wild sharks. To achieve these results, we interrogate simulated and real tracking data with the explicit purpose of drawing attention to the key considerations in the use and interpretation of inference methods and their impact on resultant social structure. We provide a modified translation of the GMMEvents method for R, including new analyses quantifying the directionality and duration of social events with the aim of encouraging the careful use of these methods more widely in less tractable social animal systems but where passive telemetry is already widespread
Network Analysis and Theory in Shark Ecology - Methods and Applications
No full textInternational audienc
Visual and Auditory Recognition Memory: An Examination of the Impact of Emotional Valence and Arousal Words on Aging and Remembering
No full textVisual recognition memory research has shown conflicting findings when using the standard remember/know procedure (Gardiner, 1988; Tulving, 1985) to examine the impact of emotional valence and arousal items on adult aging and remembering. It has been suggested that the reason for the conflicting findings within visual recognition memory research is that the standard remember/know procedure inaccurately measures the remember and know responses that represent the dual-process theory of recognition memory (Jacoby et al., 1997). However, research from other perspectives such as the socioemotional selectivity theory (Carstensen et al., 2003) and the theory of response bias (e.g. Thapar & Rouder, 2009) has also produced conflicting findings when investigating the impact of visual emotions on adult aging and remembering, indicating that the conflicting findings within visual recognition memory research may not be due to the inaccuracy of the standard remember/know procedure. In addition, there is no evidence to suggest whether these conflicting findings extent to the study of auditory recognition memory also. Therefore, the present study uses the standard remember/know procedure, a modified remember/know procedure (Sheridan & Reingold, 2011), the response bias ‘C’ measure (Ingham, 1970), and visual and auditory self-relevance questionnaires created for the present study based on the notion of the socioemotional selectivity theory were used to investigate whether there is a significant differences between younger, middle aged and older adults visual and auditory recognition memory performance for positive, negative and neutral valence (neutral arousal) words. Based on the results of the remember/know, response bias and self-relevance data, the visual and auditory standard and modified remember/know procedures produced conflicting findings between the three adult age groups and the response bias measure revealed that response bias did not significantly affect remember and know responses. Interestingly, there was no significant difference between visual and auditory recognition memory performance and there were significant self-relevance scores between the three adult age groups. Essentially, researchers need to urgently reconsider the type of remember/know procedure that they use to in future studies to research the impact of emotions on adult aging and remembering
The Effects of Living Wage Laws: Evidence from Failed and Derailed Living Wage Campaigns
No full textLiving wage campaigns have succeeded in about 100 jurisdictions in the United States but have also been unsuccessful in numerous cities. These unsuccessful campaigns provide a better control group or counterfactual for estimating the effects of living wage laws than the broader set of all cities without a law, and also permit the separate estimation of the effects of living wage laws and living wage campaigns. We find that living wage laws raise wages of low-wage workers but reduce employment among the least-skilled, especially when the laws cover business assistance recipients or are accompanied by similar laws in nearby cities.
Dualistic sector choice and female labour supply: evidence from formal and informal sector in Cameroon
No full textIn developing countries, labour supply and activity choices are distorted by the existence of labour market imperfections restricting entry to the activity sectors or rationing the worked hours. The presence of decreasing returns to labour in the informal sector is another specific characteristic of labour market dualism in LDCs. Because of the existence of entry costs, hours rationing in the formal sector and the non-linear earnings function in the informal sector that is quasi-autarkic in labour, the usual separation theorems of the standard labour supply models do not apply. Using data from a sample of women in Yaoundé (Cameroon) in 1993, choosing their activity in different sectors, we show that formal and informal labour markets have features associated with dualism and market imperfections. By contrast with the simplified models in the literature, we estimate a non-linear non-separable integrated model of activity choice and labour supply of female workers, jointly with market imperfections. We identify the effects of explanatory variables of the preferences and the earnings functions in this simultaneous structural framework. The results show that the earnings function in the informal sector is strictly concave in hours, and positively related to the education and experience of workers and the capital of the family firm. The presence of young children has a negative impact on the latent labour supply whereas that of other female members makes easier the supply of labour which is consistent with the existence of substitutabilities in the domestic chores. Other children, age and marital status of the worker also influence the latent labour supply.
The performance of diaphragm type cellular cofferdams
No full textThe construction of water management and navigation structures often requires temporary works to exclude water to facilitate construction in the dry or at least under a lower water level within the construction area. The use of cellular cofferdams for both temporary and permanent earth/water retaining works is very common. A number of theories are presented that describe the failure mechanisms involved. These failure mechanisms were identified from model studies on circular type cofferdams are applied independent of cofferdam geometry. It is common to use diaphragm type cofferdams. To asses the validity of common failure mechanisms associated with cellular cofferdams when applied to diaphragm type cofferdams, a series of numerical modelling analyses were conducted. These were validated using field monitoring results of a large scale diaphragm type cofferdam constructed at St. Germans, Norfolk, UK.A series of plane strain analyses of a diaphragm type cofferdam were conducted using the geometry from a critical section of cofferdam. These analyses identified the lowest factor of safety based on the drained strength of the clay on which the cofferdam was constructed. The water level within the river was increased to accommodate flooding and soil strength was reduced to identify the general failure mechanism. The structural forces were calculated using both 2D and 3D models for a larger width section (13m wide) to allow comparison with wall bending moments and displacements measured in field. The 3D analyses used actual tie spacing and membrane effects whilst reducing the lateral stiffness of the wall to accommodate the stiffness reduction due to variation in the interlock forces.To measure the bending moment in sheet piles, resistance type strain gauges were installed on a 13m wide section of cofferdam. The cell deflection, river and cell water levels were also monitored to identify tidal river effect and the influence of cell water level on performance. Comparison of field and numerical results highlighted a number of important design and construction detail related to diaphragm type cellular cofferdams
Satellite Remote Sensing in Shark and Ray Ecology, Conservation and Management
No full textGlobal elasmobranch populations have declined dramatically over the past 50 years, and continued research into the drivers of their habitats and distributions is vital for improved conservation and management. How environmental factors influence elasmobranch behavior, habitat use, and movement patterns is still relatively poorly understood, in part because of the scale over which many of these animals roam and the remote nature of the marine ecosystems they inhabit. In the last decade there has been an explosion of satellite remote sensing (SRS) technologies that can cover these vast spatial scales for the marine environment. Consequentially, SRS presents an opportunity to analyze important environmental drivers in elasmobranch ecology and to aid management decisions for the conservation of declining populations. A systematic literature review was undertaken to synthesize the current use of SRS environmental data in elasmobranch research. In addition, to facilitate the use of SRS in this field moving forward, we have compiled a list of popular SRS data sources and sensors for common environmental variables in marine science. Our review of 71 papers (55 published in the last 10 years) identified ten SRS-derived environmental variables that have been used in elasmobranch studies, from a range of satellite sensors and data sources. Sea surface temperature and ocean productivity were the most frequently used variables. Articles primarily analyzed variables individually or in pairs, with few studies looking at a suite of interacting variables. Here, we present a summary of the current state of knowledge on the application of SRS, current gaps and limitations, and discuss some of the potential future directions in which we envisage this field developing. Threatened elasmobranch populations inhabit some of the world’s most remote marine ecosystems. With often global coverage, SRS presents an opportunity to analyze the important environmental drivers of elasmobranch ecology to aid management decisions for the conservation of declining and threatened populations
Multiyear social stability and social information use in reef sharks with diel fission–fusion dynamics
No full textFunding: Field research at Palmyra was supported by funds from the Marisla Foundation. D.M.P.J. was supported by the Bertarelli Foundation and the project contributed to the Bertarelli Programme in Marine Science. Acknowledgements: We thank K. Davis, P. Carlson, C. Lowe, and K. Weng for assistance with fieldwork, the staff of The Nature royalsocietypublishing.org/journal/rspb Proc. R. Soc. B 287: 20201063 Conservancy that run the research station at Palmyra, and USFWS. We thank Y. Watanabe for providing camera data-loggers used in the study. Finally we thank the reviewers whose comments improved the manuscript. We declare that no authors have any conflicts of interest. This is contribution no. 156 from the Palmyra Atoll Research Consortium (PARC). This is contribution no. 206 from the Coastlines and Oceans Division of the Institute of Environment at Florida International UniversityPeer reviewe
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