Megaherbivores Modify Trophic Cascades Triggered by Fear of Predation in an African Savanna Ecosystem.

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  • Additional Information
    • Source:
      Publisher: Cell Press Country of Publication: England NLM ID: 9107782 Publication Model: Print-Electronic Cited Medium: Internet ISSN: 1879-0445 (Electronic) Linking ISSN: 09609822 NLM ISO Abbreviation: Curr Biol Subsets: MEDLINE
    • Publication Information:
      Publication: Cambridge, MA : Cell Press
      Original Publication: London, UK : Current Biology Ltd., c1991-
    • Subject Terms:
      Body Size* ; Fear* ; Grassland* ; Herbivory* ; Predatory Behavior*; Mammals/*physiology; Animals ; Mammals/psychology ; South Africa
    • Abstract:
      The loss of apex consumers (large mammals at the top of their food chain) is a major driver of global change [1]. Yet, research on the two main apex consumer guilds, large carnivores [2] and megaherbivores [3], has developed independently, overlooking any potential interactions. Large carnivores provoke behavioral responses in prey [1, 4], driving prey to distribute themselves within a "landscape of fear" [5] and intensify their impacts on lower trophic levels in low-risk areas [6], where they may concentrate nutrients through localized dung deposition [7, 8]. We suggest, however, that megaherbivores modify carnivore-induced trophic cascades. Megaherbivores (>1,000 kg [9]) are largely invulnerable to predation and should respond less to the landscape of fear, thereby counteracting the effects of fear-triggered trophic cascades. By experimentally clearing plots to increase visibility and reduce predation risk, we tested the collective role of both apex consumer guilds in influencing nutrient dynamics in African savanna. We evaluated whether megaherbivores could counteract a behaviorally mediated trophic cascade by redistributing nutrients that accumulate through fear-driven prey aggregations. Our experiment showed that mesoherbivores concentrated fecal nutrients in more open habitat, but that megaherbivores moved nutrients against this fear-driven nutrient accumulation by feeding within the open habitat, yet defecating more evenly across the risk gradient. This work adds to the growing recognition of functional losses that are likely to have accompanied megafaunal extinctions by contributing empirical evidence from one of the last systems with a functionally complete megaherbivore assemblage. Our results suggest that carnivore-induced trophic cascades work differently in a world of giants.
      (Copyright © 2018 Elsevier Ltd. All rights reserved.)
    • Comments:
      Comment in: Curr Biol. 2018 Aug 6;28(15):R835-R837. (PMID: 30086317)
    • Contributed Indexing:
      Keywords: Hluhluwe-iMfolozi Park; apex consumers; consumer-driven nutrient transport; defecation; landscape of fear; megaherbivores; nutrient distribution; predation risk; trophic cascades
    • Publication Date:
      Date Created: 20180724 Date Completed: 20191018 Latest Revision: 20191018
    • Publication Date:
      20240829
    • Accession Number:
      10.1016/j.cub.2018.05.088
    • Accession Number:
      30033334