Dietary overlap among coral-feeding butterflyfishes (Chaetodontidae) at Lizard Island, northern Great Barrier Reef

Abstract

This study documented the range of corals, and other prey types, consumed by 20 species of but- terflyfishes, which co-occur at Lizard Island, northern Great Barrier Reef, Australia. Six species (Chaetodon aureofasciatus, C. baronessa, C. lunulatus, C. plebius, C. rainfordi and C. trifascialis) fed almost exclusively on scleractinian corals, and a further eight species (C. citrinellus, C. kleinii, C. lunula, C. melannotus, C. rafflesi, C. speculum, C. ulietensis,and C. unima- culatus) took a significant proportion of their bites from corals. The other six species (C. auriga, C. ep- hippium, C. lineolatus, C. semeion, C. vagabundus, and Chelmon rostratus) rarely consumed coral, but fed on small discrete prey items from non-coral substrates. Coral-feeding butterflyfishes consumed a wide range of corals. Chaetodon lunulatus, for example, consumed 51 coral species from 24 different genera. However, there was up to 72% dietary overlap between coral-feeding butterflyfishes, with 11/14 species feeding predomi- nantly on Acropora hyacinthus or Pocillopora dami- cornis. The most specialised corallivore, C. trifascialis, took 88% of bites from A. hyacinthus. Chaetodon tri- fascialis defend territories encompassing one or more colonies of A. hyacinthus, and may have prevented other species such as C. lunulatus from feeding even more extensively on this coral. This study has shown that coexistence of coral-feeding butterflyfishes occurs despite an apparent lack of partitioning of prey resources. While different coral-feeding butterflyfishes were more or less selective in their use of different coral prey, virtually all species fed predominantly on A. hyacinthus or P. damicornis.