Abstract

Feeding habits and territorial behaviour of four sympatric Red Sea butterflyfishes were investigated in Eritrean coastal waters. Individual bite rates and types of food consumed were recorded. Stomach contents of 125 specimens were analysed in the laboratory. The food items in the stomach were sorted and their volume estimated. The four species showed marked variation in their food preferences and feeding habits. The most abundant, Chaetodon larvatus, an obligate corallivore, forms monogamous pairs. Each pair defends a relatively small territory against conspecifics and C. semilarvatus. The latter species also feeds on scleractinian corals but is solitary or lives in small aggregations. The third species, Heniochus intermedius, feeds on non-coralline benthic invertebrates (mainly polychaetes); it usually lives in pairs or in aggregations of up to 24 individuals. Both C. semilarvatus and H. intermedius occupy undefended and overlapping home ranges. The least abundant species, C. mesoleucos, forms monogamous pairs, defends a territory and feeds mainly on non-coralline benthic invertebrates (mainly nematodes and polychaetes). The four species co-exist in the same habitat where they partition the food resources. Both C. larvatus and C. semilarvatus feed on scleractinian corals, but at different times; C. larvatus was observed to feed only during daytime, but C. semilarvatus feeds by day and night.