Parental females of a nest-brooding cichlid improve and benefit from the protective value of young masquerading as snails

Abstract

Masquerade is a strategy whereby prey animals resemble environmental objects (e.g. twigs, bird droppings and stones) or inedible animals to avoid predatory attack. However, most studies of this strategy have been restricted to only a few animal groups. Therefore, novel examples are required to elucidate the diversity of masquerade strategies. Neolamprologus furcifer is a maternal nest-brooding cichlid inhabiting shaded areas of large rocks in Lake Tanganyika. In contrast to the cryptic, dark brown adults, the small young have well-defined white stripes on their brown trunk in nest territories where many white-striped snails Reymondia horei are present. We hypothesized that young N. furcifer masquerade as the model snail R. horei. We found four results consistent with our hypothesis. (1) The size, coloration, shape and posture of the young fish resembled those of the snail. (2) Experimental removal of the model snail from territories caused females to attack predators more frequently than before the removal, indirectly suggesting the protective value of the young fish's coloration. (3) Parental females selectively removed nonmodel snails from their territory, probably causing the higher density of R. horei observed at nest sites. (4) Guarded young had black/white coloration only in populations where the model snails were present. Therefore, we suggest that young N. furcifer masquerade as the model snail R. horei. This study describes a novel masquerade pattern in which the protective value is improved by, and beneficial to, a third party.