FACTORS AFFECTING THE BEHAVIOR OF CROWN-OF-THORNS STARFISH (ACANTHASTER-PLANCI L.) ON THE GREAT-BARRIER-REEF - 2 - FEEDING PREFERENCES

The feeding behaviour of the crown-of-thorns starfish, Acanthaster pla nci (L.), was studied on fifteen reefs of the Great Barrier Reef betwe en June 1986 and December 1987. Feeding preferences of A. planci for t he ten most common genera and six most common forms of scleractinian c orals were defined by pairwise comparisons of the corals being preyed upon and its nearest neighbouring coral. The preferences were quantifi ed using a novel approach, the Bradley-Terry model, and shown to form a well-ordered hierarchy. Acropora was the most preferred genus, being favoured 14:1 over Porites, the least preferred. When feeding on Acro pora, A. planci showed a preference for tabular corals over other form s. Taken over all genera, tabular forms were preferred 35:1 over massi ves, the least preferred form, and branching, submassive and foliaceou s forms were equally preferable, being favoured about 7:1 over massive s. Genera and form preference were shown to be strongly dependent with tabular and branching forms of Acropora preferred over similar forms of Montipora, but for foliaceous and encrusting forms, this pattern wa s reversed. A. planci were shown to spend longer on larger corals, wit h feeding times proportional to the colony diameter raised to the powe r of 0.72. Feeding preferences adjusted for colony size were estimated , and the preference for Acropora was generally reduced, in the case o f Porites to 8:1. The preference of A. planci for Acroporidae over oth er corals decreased moderately with deceasing relative abundance of Ac roporidae. Overall, these findings were relatively consistent across a ll reefs surveyed, suggesting that the starfish's preference for parti cular types and forms of corals were not greatly influenced by factors such as starfish density or size, time of day, or depth. (C) 1998 Els evier Science B.V.