Breeding Performance and Pond Habitat Management of Critically Endangered Black Soft-Shell Turtle (Nilssonia nigricans) in Bangladesh

Abstract

Approximately 450–550 critically endangered soft-shell turtles locally known as Bostami turtle (Nilssonia nigricans) are confined in a freshwater reservoir (earthen pond) of 5663.24 m2 (84.4 m × 67.1 m) at a shrine in Chattogram, Bangladesh. The shrine is visited by many people and feed these turtles for religious purposes. These turtles are remained half-buried in the mud during the day and also floating, taking rest and feeding in this single pond. A survey was conducted with the shrine authority, visitors as well as observed management protocol to understand the status of Bostami turtle. Their nesting season extends from February to May. The median clutch size was 16.5 (range 16–30). The incubation period was varied from 80–90 days and the successful hatching rate was significantly low (P = 0.03) and gradually decreased from 13.1% to 7.14% in 2008 to 2010. Limited cruising area, eggs predation, overcrowding, lack of proper nesting ground, lack of proper hatching and management facilities are the major threats for this critically endangered fresh water turtle. A poor management could potentially bring health risk and inbreeding depression in the population. All sorts of biological activities in a single pond for an endangered species could potentially bring disaster and appropriate management protocol should be followed. Thus, a standard management protocol of soft-shell turtle has been developed in this study for proper management of Bostami turtle.