Grazing halos on coral reefs: predation risk, herbivore density, and habitat size influence grazing patterns that are visible from space

Bartholomew P. DiFiore*, Simon A. Queenborough, Elizabeth M.P. Madin, Valerie J. Paul, Mary Beth Decker, Adrian C. Stier

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    13 Citations (Scopus)


    The behavior of organisms at local scales can have dramatic effects on the distribution of habitat and ecosystem processes at large spatial scales. Grazing halos — barren areas of sand surrounding coral reefs — are readily visible in remotely sensed imagery, and are formed by herbivores preferentially grazing close to the safety of the reef. Grazing halo size can vary by more than an order of magnitude, yet we lack an understanding of what underlies this variation. Changes in grazing intensity and the distance herbivores travel may be influenced by predation risk, resource availability, and structural attributes of the reef. Here, we tested how predator density, herbivore density, and patch reef area are correlated with halo size and grazing patterns by linking satellite imagery with mensurative experiments on patch reefs in the Caribbean. Chronic predation risk suppressed the overall foraging intensity of herbivorous fishes; a doubling in predator density led to a 29% decrease in grazing. Variation in herbivore density, which was tightly correlated with patch reef area, was linked to the distance herbivores foraged from the reef. Furthermore, herbivore density and/or reef area was the best predictor of halo width at field sites, and reef area explained a significant proportion of the variation in halo size across the landscape. Our results contribute to a growing body of research suggesting that halos may function as footprints of ecological processes, such as herbivory, that can be quantified using remote sensing, and offer a potential avenue to improve monitoring of coral reef management.

    Original languageEnglish
    Pages (from-to)71-81
    Number of pages11
    JournalMarine Ecology Progress Series
    Publication statusPublished - 26 Sep 2019

    Bibliographical note

    Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.


    • Foraging ecology ·
    • Herbivory
    • Landscape ecology
    • Predation risk
    • Predator−prey interaction
    • Remote
    • Seagrass
    • Sensing
    • ·


    Dive into the research topics of 'Grazing halos on coral reefs: predation risk, herbivore density, and habitat size influence grazing patterns that are visible from space'. Together they form a unique fingerprint.

    Cite this