Factors affecting the behaviour 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 planci (L.), was studied on fifteen reefs of the Great Barrier Reef between June 1986 and December 1987. Feeding preferences of A. planci for the ten most common genera and six most common forms of scleractinian corals were defined by pairwise comparisons of the corals being preyed upon and its nearest neighbouring coral. The preferences were quantified 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 Acropora, A. planci showed a preference for tabular corals over other forms. Taken over all genera, tabular forms were preferred 35:1 over massives, the least preferred form, and branching, submassive and foliaceous forms were equally preferable, being favoured about 7:1 over massives. 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 was reversed. A. planci were shown to spend longer on larger corals, with feeding times proportional to the colony diameter raised to the power of 0.72. Feeding preferences adjusted for colony size were estimated, and the preference for Acropora was generally reduced, in the case of Porites to 8:1. The preference of A. planci for Acroporidae over other corals decreased moderately with deceasing relative abundance of Acroporidae. Overall, these findings were relatively consistent across all reefs surveyed, suggesting that the starfish's preference for particular types and forms of corals were not greatly influenced by factors such as starfish density or size, time of day, or depth. (C) 1998 Elsevier Science B.V.