The range of the Desert Monitor Varanus griseus caspius (Eichwald, 1831) in Central Asia

Abstract

In more recent publications, the range of Central Asian Desert Monitor Varanus griseus caspius (Eichwald, 1831) for entire Central Asia, as well as for individual republics, is shown either quite conditionally and in general terms, or distribution maps are presented as points of findings. We summarized and analyzed all available sources of information regarding the distribution of the Central Asian Desert Monitor, plotted the existing points of findings on the map, conducted modeling of the potential distribution of the monitor, and, comparing the result with the map of the anthropogenic modified landscape, delineated the modern range of the Desert Monitor in Central Asia. Modeling the potential range using various environmental factor variables allowed us to supplement factual data and construct a more detailed map of the Desert Monitor’s range. The modeling was performed using the maximum entropy method in the Maxent software. The modeling results showed that the most significant factors for model construction were the mean temperature of the driest quarter, as well as the normalized difference vegetation index (March), precipitation during the warmest quarter, precipitation (March), and solar radiation (April). Consolidating all available information, we were able to update the distribution map of the Desert Monitor in Central Asia, and the classification of findings by periods along with the anthropogenic landscape map allowed us to assess the degree of its range change since the mid-last century. It was found that the monitor’s range has significantly decreased in many regions due to the “expansion” of an anthropogenically altered landscape. The most considerable range reduction, relative to the past, occurred in Uzbekistan, Tajikistan, and Kyrgyzstan. To a lesser extent, the range decreased in Turkmenistan, and very slightly in Kazakhstan. Data analysis allowed updating the distribution map of the Desert Monitor in Central Asia, revealing a significant decrease in its range in many regions since the mid-last century. The study revealed that the main reasons for the shrinking range of the Desert Monitor in Central Asia are associated with the transformation of anthropogenic landscapes, particularly in Uzbekistan, Tajikistan, and Kyrgyzstan. Modeling showed that the primary factors determining the distribution of the Desert Monitor are climatic conditions, such as the mean temperature of the driest quarter, the normalized difference vegetation index for March, precipitation during the warmest quarter, precipitation for March, and solar radiation in April. The resulting map of the Desert Monitor’s distribution in Central Asia serves as an important tool for conservation and management of this species’ populations, as well as for the development of nature conservation programs. Further field research is necessary to confirm modeling predictions and identify areas where monitor presence has not been previously confirmed, especially in regions where the monitor’s range remains incompletely explored.