Identifying landscape factors affecting tiger decline in the Bangladesh Sundarbans

Abstract

The Sundarbans Forest (∼10,000 km2) represents the only mangrove ecosystem inhabited by tigers Panthera tigris. However, in the Bangladesh portion of the Sundarbans (∼6,000 km2) tigers appear to have declined. The aim of this study was to examine the influence of a range of environmental and landscape variables in possible changes in the relative abundance of tigers in the Bangladesh Sundarbans over a five-year period (2007–2011). In 2007, 2011 tiger relative abundance was assessed using sign surveys. Using regression models we investigated changes in relative abundance versus multiple landscape variables (human disturbance associated with villages and commercial shipping lanes, distance to the international border with India where there is enhanced patrolling, presence of forest guard stations, number of criminal prosecutions and forest protection status). Tiger relative abundance was higher in 2007 and declined by 2011 with changes best explained by the proximity to international boundaries. This result might have been affected by the high levels of security patrols at the India-Bangladesh border along with cross border tiger movement between India and Bangladesh. Neighboring tiger range countries could strengthen cross-border law enforcement, increasing protection of dispersing animals. Particularly alarming was the absence of a positive effect of protected areas relative to those outside the protected area system or forest guard stations, implying a lack of management effectiveness suggesting an urgent need for an improved strategy for managing tigers and their habitats.