New publication: Food provisioning increases the risk of injury to dolphins

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In close collaboration with the Sarasota Dolphin Research Program, Florida, we are delighted to bring to your attention a recent paper by researchers from Murdoch University, Sarasota Dolphin Research Program, Chicago Zoological Society and University of Aberdeen in Scotland published in Royal Society Open Science

Title of the paper: Food provisioning increases the risk of injury in a long-lived marine top predator

Full citation: Christiansen F, McHugh KABejder L, Siegal EM, Lusseau D, McCabe EB, Lovewell G and Wells RS. 2016 Food provisioning increases the risk of injury in a long-lived marine top predator. Royal Society Open Science 3: 160560. DOI: 10.1098/rsos.160560

Abstract:

Food provisioning of wildlife is a major concern for management and conservation agencies worldwide because it encourages unnatural behaviours in wild animals and increases each individual’s risk for injury and death. Here we investigate the contributing factors and potential fitness consequences of a recent increase in the frequency of human interactions with common bottlenose dolphins (Tursiops truncatus) in Sarasota Bay, Florida. A rising proportion of the local long-term resident dolphin community is becoming conditioned to human interactions through direct and indirect food provisioning (Figure 1). We investigate variables that are affecting conditioning and if the presence of human-induced injuries is higher for conditioned versus unconditioned dolphins. Using the most comprehensive long-term dataset available for a free-ranging bottlenose dolphin population (>45 years; >32 000 dolphin group sightings; more than 1100 individuals), we found that the association with already conditioned animals strongly affected the probability of dolphins becoming conditioned to human interactions, confirming earlier findings that conditioning is partly a learned behaviour. More importantly, we found that conditioned dolphins were more likely to be injured by human interactions when compared with unconditioned animals (Image 1; Figure 2). This is alarming, as conditioning could lead to a decrease in survival, which could have population-level consequences.We did not find a significant relationship between human exposure or natural prey availability and the probability of dolphins becoming conditioned. This could be due to low sample size or insufficient spatio-temporal resolution in the available data. Our findings show that wildlife provisioning may lead to a decrease in survival, which could ultimately affect population dynamics.

The cumulative number of conditioned dolphins (solid line) observed over the study period (1993-2014). The core dolphin population size (dashed line), representing animals seen during at least four months or two seasons of the year within the core study area based on all field, is shown for comparison. The horizontal bars indicate the time periods covered by the different data sets used in this study. Note that the cumulative number of conditioned animals does not account for conditioned animals that died during the study.

Figure 1. The cumulative number of conditioned dolphins (solid line) observed over the study period (1993-2014). The core dolphin population size (dashed line), representing animals seen during at least four months or two seasons of the year within the core study area based on all field, is shown for comparison. The horizontal bars indicate the time periods covered by the different data sets used in this study. Note that the cumulative number of conditioned animals does not account for conditioned animals that died during the study.

 

An adult male dolphin (Noah; F188) victim of severe boat strikes. F188's propeller wounds occurred in 2012, and he has since healed on his own and is still alive. The animal had been conditioned to indirect provisioning (observed patrolling and either scavenging or depredating from recreational fishermen). Sarasota Dolphin Research Program. Images taken under National Marine Fisheries Service Scientific Research Permit No. 15543.

Image 1. An adult male dolphin (F188) victim of severe boat strikes. F188’s propeller wounds occurred in 2012, and he has since healed on his own and is still alive. The animal had been conditioned to indirect provisioning (observed patrolling and either scavenging or depredating from recreational fishermen). Sarasota Dolphin Research Program. Images taken under National Marine Fisheries Service Scientific Research Permit No. 15543.

Figure 2. Probability of injury as a function of age for conditioned (black solid line) and unconditioned (grey solid line) bottlenose dolphins. The solid lines represent the fitted values of the generalized linear model. The dotted lines represent 95% confidence intervals. The distribution of age values for conditioned and unconditioned dolphins are shown by the top and bottom rug plots, respectively. n=404.

 

Download the paper: The article can be downloaded HERE, or alternatively, please email Fredrik Christiansen for a PDF at f.christiansen@murdoch.edu.au

Lars Bejder PhD
Lars Bejder PhD
Professor Lars Bejder PhD is the Research Leader of the Murdoch University Cetacean Research Unit.
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Comments

  • Elizabeth walsh

    Great Work well done . I love dolphins and I do volunteering at bunbury dolphin discovery centre and I was also involve that Murdoch GPS data collection when John symson was with Marin in 2016 I joined.

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