Age and sex-selective predation moderate the overall impact of predators

Sarah R Hoy, Steve J Petty, Alexandre Millon, D Philip Whitfield, Michael Marquiss, Martin Davison, Xavier Lambin

Research output: Contribution to journalArticle

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Abstract

Currently, there is no general agreement about the extent to which predators impact prey population dynamics and it is often poorly predicted by predation rates and species abundances. This could, in part be caused by variation in the type of selective predation occurring. Notably, if predation is selective on categories of individuals that contribute little to future generations, it may moderate the impact of predation on prey population dynamics. However, despite its prevalence, selective predation has seldom been studied in this context. Using recoveries of ringed tawny owls (Strix aluco) predated by 'superpredators', northern goshawks (Accipiter gentilis) as they colonized the area, we investigated the extent to which predation was sex and age-selective. Predation of juvenile owls was disproportionately high. Amongst adults, predation was strongly biased towards females and predation risk appeared to increase with age. This implies age-selective predation may shape the decline in survival with age, observed in tawny owls. To determine whether selective predation can modulate the overall impact of predation, age-based population matrix models were used to simulate the impact of five different patterns of age-selective predation, including the pattern actually observed in the study site. The overall impact on owl population size varied by up to 50%, depending on the pattern of selective predation. The simulation of the observed pattern of predation had a relatively small impact on population size, close to the least harmful scenario, predation on juveniles only. The actual changes in owl population size and structure observed during goshawk colonization were also analysed. Owl population size and immigration were unrelated to goshawk abundance. However, goshawk abundance appeared to interact with owl food availability to have a delayed effect on recruitment into the population. This study provides strong evidence to suggest that predation of other predators is both age and sex-selective and that selective predation of individuals with a low reproductive value may mitigate the overall impact of predators on prey population dynamics. Consequently, our results highlight how accounting for the type of selective predation occurring is likely to improve future predictions of the overall impact of predation.

Original languageEnglish
Pages (from-to)692-701
Number of pages10
JournalJournal of Animal Ecology
Volume84
Issue number3
Early online date3 Dec 2014
DOIs
Publication statusPublished - May 2015

Fingerprint

predation
predator
predators
gender
Strigiformes
population size
Accipiter gentilis
population dynamics
Strix
predation risk
food availability
immigration
population structure
colonization

Keywords

  • Accipiter gentilis
  • mesopredator
  • northern goshawk
  • population dynamics
  • predatory interactions
  • recruitment
  • senescence
  • Strix aluco
  • superpredator
  • tawny owl

Cite this

Age and sex-selective predation moderate the overall impact of predators. / Hoy, Sarah R; Petty, Steve J; Millon, Alexandre; Whitfield, D Philip; Marquiss, Michael; Davison, Martin; Lambin, Xavier.

In: Journal of Animal Ecology, Vol. 84, No. 3, 05.2015, p. 692-701.

Research output: Contribution to journalArticle

Hoy, Sarah R ; Petty, Steve J ; Millon, Alexandre ; Whitfield, D Philip ; Marquiss, Michael ; Davison, Martin ; Lambin, Xavier. / Age and sex-selective predation moderate the overall impact of predators. In: Journal of Animal Ecology. 2015 ; Vol. 84, No. 3. pp. 692-701.
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author = "Hoy, {Sarah R} and Petty, {Steve J} and Alexandre Millon and Whitfield, {D Philip} and Michael Marquiss and Martin Davison and Xavier Lambin",
note = "{\circledC} 2014 The Authors. Journal of Animal Ecology published by John Wiley & Sons Ltd on behalf of British Ecological Society. Acknowledgements: Thanks to J. Reid, S. Redpath, A. Beckerman and an anonymous reviewer for their helpful comments on a previous version of the manuscript. This work was partly funded by a Natural Environment Research Council studentship NE/J500148/1 to SH and a grant NE/F021402/1 to XL and by Natural Research Limited. Forest Research funded all the fieldwork on goshawks, tawny owls and field voles during 1973–1996. We thank B. Little, P. Hotchin, D. Anderson and all field assistants for their help with data collection and Forest Enterprise, T. Dearnley and N. Geddes for allowing and facilitating work in Kielder Forest. In addition, we are grateful to English Nature and the BTO for kindly issuing licences annually visit goshawk nest sites. Data accessibility: All data associated with the study which have not already been given in the text are available from the Dryad Digital Repository: http://doi.org/10.5061/dryad.h1289 (Hoy et al. 2014).",
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AU - Petty, Steve J

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AU - Davison, Martin

AU - Lambin, Xavier

N1 - © 2014 The Authors. Journal of Animal Ecology published by John Wiley & Sons Ltd on behalf of British Ecological Society. Acknowledgements: Thanks to J. Reid, S. Redpath, A. Beckerman and an anonymous reviewer for their helpful comments on a previous version of the manuscript. This work was partly funded by a Natural Environment Research Council studentship NE/J500148/1 to SH and a grant NE/F021402/1 to XL and by Natural Research Limited. Forest Research funded all the fieldwork on goshawks, tawny owls and field voles during 1973–1996. We thank B. Little, P. Hotchin, D. Anderson and all field assistants for their help with data collection and Forest Enterprise, T. Dearnley and N. Geddes for allowing and facilitating work in Kielder Forest. In addition, we are grateful to English Nature and the BTO for kindly issuing licences annually visit goshawk nest sites. Data accessibility: All data associated with the study which have not already been given in the text are available from the Dryad Digital Repository: http://doi.org/10.5061/dryad.h1289 (Hoy et al. 2014).

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N2 - Currently, there is no general agreement about the extent to which predators impact prey population dynamics and it is often poorly predicted by predation rates and species abundances. This could, in part be caused by variation in the type of selective predation occurring. Notably, if predation is selective on categories of individuals that contribute little to future generations, it may moderate the impact of predation on prey population dynamics. However, despite its prevalence, selective predation has seldom been studied in this context. Using recoveries of ringed tawny owls (Strix aluco) predated by 'superpredators', northern goshawks (Accipiter gentilis) as they colonized the area, we investigated the extent to which predation was sex and age-selective. Predation of juvenile owls was disproportionately high. Amongst adults, predation was strongly biased towards females and predation risk appeared to increase with age. This implies age-selective predation may shape the decline in survival with age, observed in tawny owls. To determine whether selective predation can modulate the overall impact of predation, age-based population matrix models were used to simulate the impact of five different patterns of age-selective predation, including the pattern actually observed in the study site. The overall impact on owl population size varied by up to 50%, depending on the pattern of selective predation. The simulation of the observed pattern of predation had a relatively small impact on population size, close to the least harmful scenario, predation on juveniles only. The actual changes in owl population size and structure observed during goshawk colonization were also analysed. Owl population size and immigration were unrelated to goshawk abundance. However, goshawk abundance appeared to interact with owl food availability to have a delayed effect on recruitment into the population. This study provides strong evidence to suggest that predation of other predators is both age and sex-selective and that selective predation of individuals with a low reproductive value may mitigate the overall impact of predators on prey population dynamics. Consequently, our results highlight how accounting for the type of selective predation occurring is likely to improve future predictions of the overall impact of predation.

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KW - Accipiter gentilis

KW - mesopredator

KW - northern goshawk

KW - population dynamics

KW - predatory interactions

KW - recruitment

KW - senescence

KW - Strix aluco

KW - superpredator

KW - tawny owl

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DO - 10.1111/1365-2656.12310

M3 - Article

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SP - 692

EP - 701

JO - Journal of Animal Ecology

JF - Journal of Animal Ecology

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