Present and Future Suitability of the Lake Tana Biosphere Reserve (LTBR) in Ethiopia for the Nile monitor (Varanus niloticus) using the MaxEnt Mode

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Abstract BackgroundThe Nile monitor (Varanus niloticus) is a reptile native to Sub-Saharan Africa along the Nile River. The species inhabits a wide variety of habitats including woodlands, grasslands, mangroves, and swamps. Although the practice is not common in the Lake Tana Biosphere Reserve (LTBR) , the species is being hunted in Sahelian Africa for its leather, food, pet trade and fat-content. Consequently, the species is listed under the Convention on International Trade in Endangered Species. MethodsData collection was based on original onsite GIS aided presence recording. Each record of the species was first vetted for data quality. A multicollinearity analysis was conducted before fitting the MaxEnt model to the 19 bioclimatic variables. Since it provides good coverage for Africa, the Hadley Global Environment Model 2-Atmosphere Ocean (HadGEM2-AO) model was used for extracting future climate scenarios. The jackknife test was selected to measure the contribution of each environmental variable to the MaxEnt model for the species. Area under the curve of the receiver operating characteristic was used to evaluate the performance of MaxEnt model. Resultson average 2750 individuals were recorded within the LTBR. Mean annual temperature, precipitation and temperature were the most important predictors that limit the potential distribution of V. niloticus. Most of its suitable habitats were mainly predicted in the northern and southern parts of the Lake. The ecological niche model produced an average AUC of 0.85. Notable records of the species were found in the vicinity of the lake and wetlands nearby. Future projection of potential suitable areas revealed that the currently available suitable area will decline in both 2050 and 2070 under both RCP 6.5 and RCP 8.5, of which the decline in suitable area under the business as usual scenario is the greatest. ConclusionsThe potential distribution map for V. niloticus can help in planning land use management around its existing habitat range, discover new populations or set priorities to restore its natural habitat for more effective conservation. Extensive reductions in the amount of suitable areas under future climate scenarios suggest that the species may become threatened in future if effective conservation measures are not implemented.

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