Modelling of Metapopulation Dynamics and Distribution of Varanus Flavescens in Nepal Tarai: Implications to Conservation

Abstract

Human presence within the Jagdishpur reservoir and associated wetlands has largely fragmented the wetland habitats. In attempt to understand the metapopulation dynamics of Golden Monitor Lizard (Varanus flavescens), these dynamics of the species were modelled from surveys of two consecutive years in 2012 and 2013. A land cover classification was performed to categorise land cover patterns and recognition of landscape variables. Surveys to determine dynamic occupancy state of the species was performed in 40 grids; 1 sq km each, enclosing Jagadishpur Reservoir and associated wetlands and analyzed in Program PRESENCE. Impact of landscape variables on species distribution and other factors used as covariates upon parameters were modelled in the program. Available presence data were modelled for predicting potentially suitable habitat using Program MAXENT. Land cover classification recognized five major landcover types with greater proportion of forest and settlement areas. Other identified classes were grassland, marshlands and bare lands distributed over the area. The study revealed higher rate of recolonization probability over local extinction rate thus higher occupancy in 2013. A patchy subpopulation type metapopulation in the study area was documented. Occupancy of Golden Monitor Lizard was shown to be negatively affected by distance to settlements while positive correlation existed between the state variable and distance to nearest water source. MAXENT model predicted entire Tarai and some river valleys as potential area but GIS analysis revealed a relatively less Extent of Occurrence available for the species. The study concluded unstable metapopulation existed as human disturbance increases. Identification and monitoring of other metapopulation of the species, providing better protection or extension of PA networks, landscape level conservation and enlistment of the species in national red data list as endangered will help to conserve the species if implicated.