Estimating spatial, temporal and individual variability in dolphin cumulative exposure to boat traffic using spatially explicit capture-recapture methods

Enrico E. Pirotta, Paul M. P.M. Thompson, Barbara B. Cheney, Carl R. C.R. Donovan, David M. D.M. Lusseau

Research output: Contribution to journalArticle

16 Citations (Scopus)

Abstract

Appropriate management of the effects of human activities on animal populations requires quantification of the rate at which animals encounter stressors. Such activities are heterogeneously distributed in space, as are the individual animals in a population. This will result in a heterogeneous exposure rate, which is also likely to vary over time. A spatially explicit analysis of individual exposure is therefore required. We applied Bayesian spatially explicit capture-recapture models to photo-identification data to estimate the home range of well-marked individuals in a protected coastal population of bottlenose dolphins. Model results were combined with the estimated distribution of boat traffic to quantify how exposure to this disturbance varied in time and space. Variability in exposure between individuals was also investigated using a mixed-effects model. The cumulative individual exposure to boat traffic varied between summers, depending both on the overall area usage and the degree of individual movement around the activity centres. Despite this variability, regions of higher risk could be identified. There were marked inter-individual differences in the predicted amount of time dolphins spent in the presence of boats, and individuals tended to be consistently over- or underexposed across summers. Our study offers a framework to describe the temporal, spatial and individual variation in exposure to anthropogenic stressors when individuals can be repeatedly identified over time. It provides opportunities to map exposure risk and understand how this evolves in time at both individual and population levels. The outcome of such modelling can be used as a robust evidence base to support management decisions.
Original languageEnglish
Pages (from-to)20-31
Number of pages12
JournalAnimal Conservation
Volume18
Issue number1
Early online date29 Apr 2014
DOIs
Publication statusPublished - Feb 2015

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dolphin
animal
individual variation
summer
home range
traffic
exposure
method
temporal variation
human activity
spatial variation
disturbance
modeling

Keywords

  • Bayesian modelling
  • Capture-recapture
  • Disturbance
  • Dolphin
  • Exposure rate
  • Home range
  • Marine traffic
  • Tursiops truncatus

Cite this

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title = "Estimating spatial, temporal and individual variability in dolphin cumulative exposure to boat traffic using spatially explicit capture-recapture methods",
abstract = "Appropriate management of the effects of human activities on animal populations requires quantification of the rate at which animals encounter stressors. Such activities are heterogeneously distributed in space, as are the individual animals in a population. This will result in a heterogeneous exposure rate, which is also likely to vary over time. A spatially explicit analysis of individual exposure is therefore required. We applied Bayesian spatially explicit capture-recapture models to photo-identification data to estimate the home range of well-marked individuals in a protected coastal population of bottlenose dolphins. Model results were combined with the estimated distribution of boat traffic to quantify how exposure to this disturbance varied in time and space. Variability in exposure between individuals was also investigated using a mixed-effects model. The cumulative individual exposure to boat traffic varied between summers, depending both on the overall area usage and the degree of individual movement around the activity centres. Despite this variability, regions of higher risk could be identified. There were marked inter-individual differences in the predicted amount of time dolphins spent in the presence of boats, and individuals tended to be consistently over- or underexposed across summers. Our study offers a framework to describe the temporal, spatial and individual variation in exposure to anthropogenic stressors when individuals can be repeatedly identified over time. It provides opportunities to map exposure risk and understand how this evolves in time at both individual and population levels. The outcome of such modelling can be used as a robust evidence base to support management decisions.",
keywords = "Bayesian modelling, Capture-recapture, Disturbance, Dolphin, Exposure rate, Home range, Marine traffic, Tursiops truncatus",
author = "Pirotta, {Enrico E.} and Thompson, {Paul M. P.M.} and Cheney, {Barbara B.} and Donovan, {Carl R. C.R.} and Lusseau, {David M. D.M.}",
note = "Funded by Scottish Funding Council. Grant Number: HR09011 Marine Scotland Scottish Natural Heritage Acknowledgements This work received funding from the MASTS pooling initiative (the Marine Alliance for Science and Technology for Scotland) and their support is gratefully acknowledged. MASTS is funded by the Scottish Funding Council (grant reference HR09011) and contributing institutions. We would like to thank Marine Scotland and Scottish Natural Heritage for partly funding this work. We would particularly like to thank Ben Leyshon for all his support. Photo-identification data were collected during a series of grants and contracts from the BES, ASAB, Greenpeace Environmental Trust, Scottish Natural Heritage, Scottish Government, Whale and Dolphin Conservation, Talisman Energy (UK) Ltd., Department of Energy and Climate Change, Chevron and the Natural Environment Research Council. All survey work was carried out under Scottish Natural Heritage Animal Scientific Licences. We also would like to thank Andrew Royle, David Borchers, Darren Kidney and Steve Palmer for their useful advice at the early stages of this work, and Fredrik Christiansen for invaluable discussions on spatially explicit capture–recapture techniques. Finally, we thank Tim Barton and all the people who have helped during data collection.",
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N1 - Funded by Scottish Funding Council. Grant Number: HR09011 Marine Scotland Scottish Natural Heritage Acknowledgements This work received funding from the MASTS pooling initiative (the Marine Alliance for Science and Technology for Scotland) and their support is gratefully acknowledged. MASTS is funded by the Scottish Funding Council (grant reference HR09011) and contributing institutions. We would like to thank Marine Scotland and Scottish Natural Heritage for partly funding this work. We would particularly like to thank Ben Leyshon for all his support. Photo-identification data were collected during a series of grants and contracts from the BES, ASAB, Greenpeace Environmental Trust, Scottish Natural Heritage, Scottish Government, Whale and Dolphin Conservation, Talisman Energy (UK) Ltd., Department of Energy and Climate Change, Chevron and the Natural Environment Research Council. All survey work was carried out under Scottish Natural Heritage Animal Scientific Licences. We also would like to thank Andrew Royle, David Borchers, Darren Kidney and Steve Palmer for their useful advice at the early stages of this work, and Fredrik Christiansen for invaluable discussions on spatially explicit capture–recapture techniques. Finally, we thank Tim Barton and all the people who have helped during data collection.

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