Title
Recovery of African wild dogs suppresses prey but does not trigger a trophic cascade
Author(s)
Ford, A.T.;Goheen, J.R.;Augustine, D.J.;Kinnaird, M.F.;O'Brien, T.G.;Palmer, T.M.;Pringle, R.M.;Woodroffe, R.
Published
2015
Publisher
Ecology
Abstract
Increasingly, the restoration of large carnivores is proposed as a means through which to restore community structure and ecosystem function via trophic cascades. After a decades-long absence, African wild dogs (Lycaon pictus) recolonized the Laikipia Plateau in central Kenya, which we hypothesized would trigger a trophic cascade via suppression of their primary prey (dik-dik; Madoqua guentheri) and the subsequent relaxation of browsing pressure on trees. We tested the trophic-cascade hypothesis using: (1) a 14-year time series of wild dog abundance; (2) surveys of dik-dik population densities conducted before and after wild dog recovery; and (3) two separate, replicated herbivore-exclusion experiments initiated before and after wild dog recovery. The dik-dik population declined by 33% following wild dog recovery, which is best explained by wild dog predation. Dik-dik browsing suppressed tree abundance, but the strength of suppression did not differ between pre- and post-wild dog recovery. Despite strong, top-down limitation between adjacent trophic levels (carnivore-herbivore and herbivore-plant), a trophic cascade did not occur, possibly because of a time lag in indirect effects, variation in rainfall, and foraging by herbivores other than dik-dik. Our ability to reject the trophic-cascade hypothesis required two important approaches: (1) temporally-replicated herbivore exclusions, separately established before and after wild dog recovery; (2) evaluating multiple drivers of variation in the abundance of dik-dik and trees. While the restoration of large carnivores is undoubtedly a conservation priority, our results suggest that indirect effects are mediated by ecological context, and that trophic cascades are not a foregone conclusion of such recoveries.
Keywords
antelope;Acacia;endangered species;food web;indirect effect;large carnivore;rain;savanna;tree cover
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PUB15489