Niche separation and comparative abundance of Boulengerula boulengeri and Scolecomorphus vittatus (Amphibia: Gymnophiona) in an East Usambara forest, Tanzania

The ecology of the sympatric caecilians Boulengerula boulengeri and Scolecomorphus vittatus was studied in Nilo Forest Reserve in the East Usambara Mountains, Tanzania. Three sampling methods (timed digging, pitfall trapping and casual visual encounter surveys of the forest floor) yielded 85 B. boulengeri, found only by digging soil, and 23 S. vittatus, mostly collected above ground. The difference between these taxa in the proportions of captures above and below ground is statistically significant and is taken to indicate different ecologies. B. boulengeri is interpreted as predominantly a burrower in soil, and S. vittatus as an animal spending more time than B. boulengeri above ground. Niche separation appears to be correlated with some morphological differences. The vast majority of all vertebrate specimens dug from the top 300 mm of soil were B. boulengeri, and this species appears to be more abundant than S. vittatus in East Usambara forest soils. As an abundant endogeic animal, B. boulengeri may play an important role in the ecology of forest soils.