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Do behavioral foraging responses of prey to predators function similarly in restored and pristine foodwebs?

Madin EM, Gaines SD, Madin JS, Link AK, Lubchenco PJ, Selden RL, Warner RR - PLoS ONE (2012)

Bottom Line: We compared these responses for two functionally distinct herbivorous prey fishes (the damselfish Plectroglyphidodon dickii and the parrotfish Chlorurus sordidus) within pairs of coral reefs in pristine and restored ecosystems in two regions of these species' biogeographic ranges, allowing us to quantify the magnitude and temporal scale of this key ecosystem variable's recovery.We demonstrate that restoration of top predator abundances also restored prey foraging excursion behaviors to a condition closely resembling those of a pristine ecosystem.Increased understanding of behavioral aspects of ecosystem change will greatly improve our ability to predict the cascading consequences of conservation tools aimed at ecological restoration, such as marine reserves.

View Article: PubMed Central - PubMed

Affiliation: Department of Ecology, Evolution and Marine Biology, University of California Santa Barbara, Santa Barbara, California, United States of America. elizabeth.madin@uts.edu.au

ABSTRACT
Efforts to restore top predators in human-altered systems raise the question of whether rebounds in predator populations are sufficient to restore pristine foodweb dynamics. Ocean ecosystems provide an ideal system to test this question. Removal of fishing in marine reserves often reverses declines in predator densities and size. However, whether this leads to restoration of key functional characteristics of foodwebs, especially prey foraging behavior, is unclear. The question of whether restored and pristine foodwebs function similarly is nonetheless critically important for management and restoration efforts. We explored this question in light of one important determinant of ecosystem function and structure--herbivorous prey foraging behavior. We compared these responses for two functionally distinct herbivorous prey fishes (the damselfish Plectroglyphidodon dickii and the parrotfish Chlorurus sordidus) within pairs of coral reefs in pristine and restored ecosystems in two regions of these species' biogeographic ranges, allowing us to quantify the magnitude and temporal scale of this key ecosystem variable's recovery. We demonstrate that restoration of top predator abundances also restored prey foraging excursion behaviors to a condition closely resembling those of a pristine ecosystem. Increased understanding of behavioral aspects of ecosystem change will greatly improve our ability to predict the cascading consequences of conservation tools aimed at ecological restoration, such as marine reserves.

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Prey excursion size and rate of movement in relation to acute predation risk for C. sordidus and P. dickii.Left-hand panels (a, c) show data from the Eastern Indo-Pacific (Line Islands); right-hand panels (b, d) are from the Central Indo-Pacific (GBR). Lines show best-fit upper 95% prediction intervals (dashed) and linear regressions (solid) based on a negative log-likelihood optimization function. Points are values for individual prey where predation risk is measured by predator biomass for C. sordidus and predator (biomass×duration) for P. dickii. Eastern Indo-Pacific (right-hand) panels are reproduced with permission from Madin et al. [13].
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pone-0032390-g003: Prey excursion size and rate of movement in relation to acute predation risk for C. sordidus and P. dickii.Left-hand panels (a, c) show data from the Eastern Indo-Pacific (Line Islands); right-hand panels (b, d) are from the Central Indo-Pacific (GBR). Lines show best-fit upper 95% prediction intervals (dashed) and linear regressions (solid) based on a negative log-likelihood optimization function. Points are values for individual prey where predation risk is measured by predator biomass for C. sordidus and predator (biomass×duration) for P. dickii. Eastern Indo-Pacific (right-hand) panels are reproduced with permission from Madin et al. [13].

Mentions: Both prey species observed, the parrotfish C. sordidus and the damselfish P. dickii, demonstrate the same qualitative pattern of declining excursion size as acute predation risk increases (Fig. 3). The effect of predation risk upon prey excursion size is most effectively measured as the maximum, rather than the mean, size of excursions that prey are willing to take. This is because predation risk should limit maximum, but not minimum, excursion sizes of prey [13], allowing prey under low risk to take either long or short excursions from shelter, but limiting those under high risk to generally only taking shorter excursions. We therefore used the upper bound of the prediction interval, rather than standard regression through the mean, to assess the effect of predation risk on prey behaviour. Slopes of all upper prediction intervals and regressions were significant at the α = 0.05 level with the exceptions of C. sordidus' regression slope in the Eastern Indo-Pacific, which was marginally significant (P = 0.06), and the upper bound of this species' relationship in the Central Indo-Pacific (P = 0.33). Acute risk is a metric of the actual predation risk to which a focal prey individual was exposed during the observation period. Therefore, the patterns shown in Fig. 3 are not based upon differences within particular reef pairs, but rather are reflective of the general trend among all fishes observed at all reefs.


Do behavioral foraging responses of prey to predators function similarly in restored and pristine foodwebs?

Madin EM, Gaines SD, Madin JS, Link AK, Lubchenco PJ, Selden RL, Warner RR - PLoS ONE (2012)

Prey excursion size and rate of movement in relation to acute predation risk for C. sordidus and P. dickii.Left-hand panels (a, c) show data from the Eastern Indo-Pacific (Line Islands); right-hand panels (b, d) are from the Central Indo-Pacific (GBR). Lines show best-fit upper 95% prediction intervals (dashed) and linear regressions (solid) based on a negative log-likelihood optimization function. Points are values for individual prey where predation risk is measured by predator biomass for C. sordidus and predator (biomass×duration) for P. dickii. Eastern Indo-Pacific (right-hand) panels are reproduced with permission from Madin et al. [13].
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3293809&req=5

pone-0032390-g003: Prey excursion size and rate of movement in relation to acute predation risk for C. sordidus and P. dickii.Left-hand panels (a, c) show data from the Eastern Indo-Pacific (Line Islands); right-hand panels (b, d) are from the Central Indo-Pacific (GBR). Lines show best-fit upper 95% prediction intervals (dashed) and linear regressions (solid) based on a negative log-likelihood optimization function. Points are values for individual prey where predation risk is measured by predator biomass for C. sordidus and predator (biomass×duration) for P. dickii. Eastern Indo-Pacific (right-hand) panels are reproduced with permission from Madin et al. [13].
Mentions: Both prey species observed, the parrotfish C. sordidus and the damselfish P. dickii, demonstrate the same qualitative pattern of declining excursion size as acute predation risk increases (Fig. 3). The effect of predation risk upon prey excursion size is most effectively measured as the maximum, rather than the mean, size of excursions that prey are willing to take. This is because predation risk should limit maximum, but not minimum, excursion sizes of prey [13], allowing prey under low risk to take either long or short excursions from shelter, but limiting those under high risk to generally only taking shorter excursions. We therefore used the upper bound of the prediction interval, rather than standard regression through the mean, to assess the effect of predation risk on prey behaviour. Slopes of all upper prediction intervals and regressions were significant at the α = 0.05 level with the exceptions of C. sordidus' regression slope in the Eastern Indo-Pacific, which was marginally significant (P = 0.06), and the upper bound of this species' relationship in the Central Indo-Pacific (P = 0.33). Acute risk is a metric of the actual predation risk to which a focal prey individual was exposed during the observation period. Therefore, the patterns shown in Fig. 3 are not based upon differences within particular reef pairs, but rather are reflective of the general trend among all fishes observed at all reefs.

Bottom Line: We compared these responses for two functionally distinct herbivorous prey fishes (the damselfish Plectroglyphidodon dickii and the parrotfish Chlorurus sordidus) within pairs of coral reefs in pristine and restored ecosystems in two regions of these species' biogeographic ranges, allowing us to quantify the magnitude and temporal scale of this key ecosystem variable's recovery.We demonstrate that restoration of top predator abundances also restored prey foraging excursion behaviors to a condition closely resembling those of a pristine ecosystem.Increased understanding of behavioral aspects of ecosystem change will greatly improve our ability to predict the cascading consequences of conservation tools aimed at ecological restoration, such as marine reserves.

View Article: PubMed Central - PubMed

Affiliation: Department of Ecology, Evolution and Marine Biology, University of California Santa Barbara, Santa Barbara, California, United States of America. elizabeth.madin@uts.edu.au

ABSTRACT
Efforts to restore top predators in human-altered systems raise the question of whether rebounds in predator populations are sufficient to restore pristine foodweb dynamics. Ocean ecosystems provide an ideal system to test this question. Removal of fishing in marine reserves often reverses declines in predator densities and size. However, whether this leads to restoration of key functional characteristics of foodwebs, especially prey foraging behavior, is unclear. The question of whether restored and pristine foodwebs function similarly is nonetheless critically important for management and restoration efforts. We explored this question in light of one important determinant of ecosystem function and structure--herbivorous prey foraging behavior. We compared these responses for two functionally distinct herbivorous prey fishes (the damselfish Plectroglyphidodon dickii and the parrotfish Chlorurus sordidus) within pairs of coral reefs in pristine and restored ecosystems in two regions of these species' biogeographic ranges, allowing us to quantify the magnitude and temporal scale of this key ecosystem variable's recovery. We demonstrate that restoration of top predator abundances also restored prey foraging excursion behaviors to a condition closely resembling those of a pristine ecosystem. Increased understanding of behavioral aspects of ecosystem change will greatly improve our ability to predict the cascading consequences of conservation tools aimed at ecological restoration, such as marine reserves.

Show MeSH
Related in: MedlinePlus