Determinants of feeding territory size in the corallivorous butterflyfish, Chaetodon multicinctus

Abstract

Both sexes of the monogamous coral-feeding butterflyfish, Chaetodon multicinctus, forage as energy maximizers, are constrained by the time available for feeding, and vigorously defend their feeding territories from intrusions by conspecific competitors. Territory area was positively correlated with coral abundance when data were pooled from coral-poor and coral-rich habitats. In contrast, male lenght and total food were correlated with territory area within the coral-rich habitat. When food supply was increased, fish attempted to defend all food within original borders but were limited by aggressive interactions with conspecifics attracted to supplemental food. When coral abundance was reduced, residents expanded their territories. In comparison, territories were adjusted as an inverse function of competitor abundance and related costs of defence. Although these experiments support competitor-mediated models of territory size, food resources are also important in that they set a lower limit for minimum territory area and, when possible, are defended in surplus by this species.