A new approach to estimate fecundity rate from inter-birth intervals

Mònica Arso Civil (Corresponding Author), Barbara Cheney, Nicola J. Quick, Paul M. Thompson, Philip S. Hammond

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Abstract

Accurate estimates of fecundity rate are key to population assessments and effectively direct conservation efforts. We present a new approach to estimate fecundity rate based on the probability of a female giving birth, conditional on a previous birth t years ago, from which an expected inter-birth interval (IBI) can be estimated. We use generalized linear mixed-effects models to account for individual and temporal variability and apply the approach to individual reproductive histories of bottlenose dolphins (Tursiops truncatus) from the east coast of Scotland. We estimate a fecundity rate of 0.222 (95% CI = 0.218–0.253) and an expected IBI of 4.49 yr (95% CI = 3.94–4.93 yr). We use simulated data samples to show that the approach produces estimates with a minimum bias of <3%. Simulations are also used to investigate the effect of the most common data-driven biases in the estimates of birth intervals and fecundity rate; we recommend longitudinal studies of at least 10 yr and capture probabilities of at least 0.3 when using this methodology. The approach may be modified to incorporate other parameters of interest and should be applicable to any population with comprehensive data on birth intervals.
Original languageEnglish
Article numbere01796
JournalEcosphere
Volume8
Issue number4
Early online date18 Apr 2017
DOIs
Publication statusPublished - Apr 2017

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birth interval
fecundity
Tursiops truncatus
dolphin
longitudinal studies
Scotland
coasts
methodology
rate
coast
history
simulation
sampling
effect

Keywords

  • birth interval
  • birth probability
  • bottlenose dolphin
  • cetaceans
  • fecundity
  • generalized linear mixed models
  • mark-recapture data

Cite this

A new approach to estimate fecundity rate from inter-birth intervals. / Arso Civil, Mònica (Corresponding Author); Cheney, Barbara; Quick, Nicola J.; Thompson, Paul M.; Hammond, Philip S.

In: Ecosphere, Vol. 8, No. 4, e01796, 04.2017.

Research output: Contribution to journalArticle

Arso Civil, Mònica ; Cheney, Barbara ; Quick, Nicola J. ; Thompson, Paul M. ; Hammond, Philip S. / A new approach to estimate fecundity rate from inter-birth intervals. In: Ecosphere. 2017 ; Vol. 8, No. 4.
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abstract = "Accurate estimates of fecundity rate are key to population assessments and effectively direct conservation efforts. We present a new approach to estimate fecundity rate based on the probability of a female giving birth, conditional on a previous birth t years ago, from which an expected inter-birth interval (IBI) can be estimated. We use generalized linear mixed-effects models to account for individual and temporal variability and apply the approach to individual reproductive histories of bottlenose dolphins (Tursiops truncatus) from the east coast of Scotland. We estimate a fecundity rate of 0.222 (95{\%} CI = 0.218–0.253) and an expected IBI of 4.49 yr (95{\%} CI = 3.94–4.93 yr). We use simulated data samples to show that the approach produces estimates with a minimum bias of <3{\%}. Simulations are also used to investigate the effect of the most common data-driven biases in the estimates of birth intervals and fecundity rate; we recommend longitudinal studies of at least 10 yr and capture probabilities of at least 0.3 when using this methodology. The approach may be modified to incorporate other parameters of interest and should be applicable to any population with comprehensive data on birth intervals.",
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note = "Funded by Department of Energy and Climate Change (UK), BES, ASAB, Greenpeace, Environmental Trust, Scottish Natural Heritage, Scottish Government, Whale and Dolphin Conservation, Talisman Energy (UK) Ltd., DECC, Chevron, Natural Environment Research Council Acknowledgments Funding for this work was provided by the Department of Energy and Climate Change (UK). 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., DECC, Chevron, and the Natural Environment Research Council. All survey work was carried out under Scottish Natural Heritage Animal Scientific Licences. The authors have no conflict of interest to declare. We thank Mark Bravington for his helpful advice at the early stages of this work and two anonymous reviewers for their useful comments on the manuscript.",
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N2 - Accurate estimates of fecundity rate are key to population assessments and effectively direct conservation efforts. We present a new approach to estimate fecundity rate based on the probability of a female giving birth, conditional on a previous birth t years ago, from which an expected inter-birth interval (IBI) can be estimated. We use generalized linear mixed-effects models to account for individual and temporal variability and apply the approach to individual reproductive histories of bottlenose dolphins (Tursiops truncatus) from the east coast of Scotland. We estimate a fecundity rate of 0.222 (95% CI = 0.218–0.253) and an expected IBI of 4.49 yr (95% CI = 3.94–4.93 yr). We use simulated data samples to show that the approach produces estimates with a minimum bias of <3%. Simulations are also used to investigate the effect of the most common data-driven biases in the estimates of birth intervals and fecundity rate; we recommend longitudinal studies of at least 10 yr and capture probabilities of at least 0.3 when using this methodology. The approach may be modified to incorporate other parameters of interest and should be applicable to any population with comprehensive data on birth intervals.

AB - Accurate estimates of fecundity rate are key to population assessments and effectively direct conservation efforts. We present a new approach to estimate fecundity rate based on the probability of a female giving birth, conditional on a previous birth t years ago, from which an expected inter-birth interval (IBI) can be estimated. We use generalized linear mixed-effects models to account for individual and temporal variability and apply the approach to individual reproductive histories of bottlenose dolphins (Tursiops truncatus) from the east coast of Scotland. We estimate a fecundity rate of 0.222 (95% CI = 0.218–0.253) and an expected IBI of 4.49 yr (95% CI = 3.94–4.93 yr). We use simulated data samples to show that the approach produces estimates with a minimum bias of <3%. Simulations are also used to investigate the effect of the most common data-driven biases in the estimates of birth intervals and fecundity rate; we recommend longitudinal studies of at least 10 yr and capture probabilities of at least 0.3 when using this methodology. The approach may be modified to incorporate other parameters of interest and should be applicable to any population with comprehensive data on birth intervals.

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