Mass coral bleaching causes population declines and mortality of coral reef species1 yet its impacts on behaviour are largely unknown. Here, we unite behavioural theory with community ecology to test whether bleaching-induced mass mortality of corals can cause consistent changes in the behaviour of coral-feeding fishes. We documented 5,259 encounters between individuals of 38 Chaetodon (butterflyfish) species on 17 reefs within the central Indo-Pacific, of which 3,828 were repeated on 10 reefs both before and after the global coral bleaching event in 2016. Aggression between butterflyfishes decreased by two-thirds following large-scale coral mortality, despite no significant change in fish abundance or community composition. Pairwise encounters were most likely to be aggressive between obligate corallivores and on reefs with high coral cover. After bleaching, the proportion of preferred Acropora corals in the diet decreased significantly (up to 85% fewer bites), with no increase in overall bite rate to compensate for the loss of these nutritionally rich corals. The observed reduced aggression at low resource levels due to nutritional deficit follows the predictions of the economic theory of aggressive behaviour2,3. Our results reveal synchronous changes in behaviour in response to coral mortality. Such changes could potentially disrupt territories4, leading to reorganization of ecological communities.

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We are grateful for funding support from VILLUM FONDEN (S.A.K., grant number 10114), the Danish National Research Foundation for support of the Center for Macroecology, Evolution and Climate (grant number DNRF96), and the Australian Research Council Centre of Excellence for Coral Reef Studies (AHB grant number CE140100020). For field assistance and logistical support, we thank N. Maginnis, L. Corner, T. Quimpo, V. Horigue and A. Roan; T. Naruse and R. Yoshida, the University of the Ryukyus Iriomote Field Station; Parks Australia and Christmas Island Divers Association; and R. Trono, A. Trono and staff of the Bontoc Seaview Guesthouse and Mabini Municipal Tourism Office, Batangas, Philippines. We also thank A. MacNeil for statistical advice and N. Graham and I. Hartley for constructive feedback on this manuscript.

Author information


  1. Lancaster Environment Centre, Lancaster University, Lancaster, UK

    • Sally A. Keith
  2. Center for Macroecology, Evolution & Climate, Natural History Museum of Denmark, University of Copenhagen, Copenhagen, Denmark

    • Sally A. Keith
  3. Australian Research Council Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, Queensland, Australia

    • Andrew H. Baird
    •  & Andrew S. Hoey
  4. Department of Environment and Agriculture, Curtin University, Perth, Western Australia, Australia

    • Jean-Paul A. Hobbs
  5. The Hydrous, San Francisco, CA, USA

    • Erika S. Woolsey
  6. Stanford University, Hasso Plattner Institute of Design & The Center for Ocean Solutions, Palo Alto, CA, USA

    • Erika S. Woolsey
  7. Marine Science Department, Faculty of Marine & Fisheries, Syiah Kuala University, Banda Aceh, Indonesia

    • N. Fadli
  8. Environmental Program, Rubenstein School of Environment and Natural Resources, University of Vermont, Burlington, VT, USA

    • Nathan J. Sanders


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S.A.K. designed the study with input from J-P.A.H., A.H.B. and N.J.S.; S.A.K., J-P.A.H., A.H.B., E.S.W. and A.S.H. collected the data; N.F. provided fieldwork support; S.A.K. analysed the data and wrote the manuscript with contributions from all authors.

Competing interests

The authors declare no competing interests.

Corresponding author

Correspondence to Sally A. Keith.

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