Food resource partitioning of a community of snakes in a swamp rainforest of south-eastern Nigeria

Abstract

The food resource partitioning in a community of snakes from a moist rainforest of south-eastern Nigeria (Eket, Akwa-Ibom State) is studied in the present paper. The community consisted of 24 different species, belonging to different families and ecological guilds: some species were terrestrial, some were semi-aquatic, and others were arboreal. Six species were primarily mammal-eating, two were bird-eating, four were lizard-eating, three were frog-eating, one species fed on both mammals and birds, and one species fed on both fish and frogs. A UPGMA tree diagram showed that three clusters of snakes are formed on the basis of their diet composition: a cluster formed by the two large arboreal species (Dendroaspis jamesoni and Boiga blandingi), another formed by the group of the terrestrial mammal-eating Calabaria reinhardti, Bitis gabonica, and Bitis nasicornis, and the third cluster formed by the lizard-eating Psammophis phillipsi, Thelotornis kirtlandii, and Gastropyxis smaragdina. The relationships between these and the other taxa remain unclear. In terms of both frequency of occurrence of the various prey types and biomass contribution of each prey type, the semi-aquatic snakes showed the narrowest niche breadth values and the terrestrial snakes showed the widest niche breadth values. The overlap values were not significantly correlated with the rank of phylogenetic distance. The mean overlap values calculated between species belonging to a same guild were significantly higher than those calculated between species belonging to different guilds, but the mean overlap values between species belonging to a same guild did not differ significantly among guilds. Prey size and predator size (total length) were positively correlated. There was no statistically significant difference between snake guilds as far as mean prey size is concerned, but the various species within each guild differed significantly in terms of mean prey size.