Population Dynamics and Behavioral Pattern of Marsh Crocodile (Crocodylus palustris Lesson, 1831) – A Dimensional Analogy between Hydro-Chemical Physiognomies and Species Richness

The study aims population dynamics and behavioral pattern of Marsh Crocodile (Crocodylus palustris Lesson, 1831) in two palustrine rural habitats of Central Gujarat, India at four sampling points (Site-I) and two stations (Site-II) from January to April, 2021 to delineate population count, behavioral pattern and scat analysis of Marsh Crocodile (MC) associated with hydro-chemical physiognomies. Prior to commencement of the study, hypothesis about effects of water quality on species richness of MC was proposed. Outcomes of study reflect high population density of MC (60) at Point-3, followed by Point-1 (34), Point-4 (32) and Point-2 (12) at Site-I (N=138). Behavioral pattern of MC was more intense in Floating (71), followed by Basking (40) and Swimming (19) (N=130, 94.20%). Population peak of MC was noted at Point-2 (75), compared to Point-1 (53) at Site-II (N=128). Here, behavioral pattern of MC was more accentuated in Basking (75), followed by Floating (24) and Yawning (14) (N=113, 88.28%). Comparatively, Site-I exhibited more richness (N=138, 51.88%) than Site-II (N=128, 48.12%), making an aggregate of 266 individuals. Comparing mean values of hydro-chemical parameters of two observation areas, void difference was observed in Temperature (18 degree Celsius each). Mean concentration of pH, Chloride, Phosphate and Nitrate was intense at Site-I compared to Site-II (8.41, 500.55 mg/L, 4.76 mg/L, 2.54 mg/L, respectively) with a disparity of 0.71, 325.78 mg/L, 2.25 mg/L and 0.05 mg/L of pH, Chloride, Phosphate, and Nitrate, respectively. Conversely, Sulphate contents was more in hydrological regime at Site-II (64.64 mg/L) compared to Site-I (12.38 mg/L) with a noteworthy discrepancy (-52.26 mg/L). Correlation between hydro-chemical parameters and species richness of MC revealed that population of MC was highly affected positively by gradient contents of Nitrate (0.929) and inversely affected by Phosphate (0.182) at Site-I. However, pH was found affecting more species richness of MC (1.293) against fewer population by Temperature (0.563) at Site-II. Findings of present study evidently proved hypothesis with appropriate adequacy in term of effects of water quality on species richness of Marsh Crocodile. Scat analysis of MC revealed higher contents of TOM (366.35%) and TOC (212.50%), followed by Nitrate (1.990 mg/gm), Sulphur (0.314 mg/gm) and Phosphorus (0.014 mg/gm). Considering above facts, it is suggested that water quality of both studied palustrine habitats should be maintained by adding up selective enrichment factors (e.g. Nitrate and pH) as a management perspectives and implicative measures. Moreover, as crocodilian scat is very rich in Organic Carbon and Organic Matter, native farmers should use it commercially (cost-benefit factors) to augment fertility and productivity of desired crop yields. Above suggestions would unfailingly be aiding tools to sustain prevailing population of Marsh Crocodiles in Central Gujarat, India.本研究旨在探究2021年1月至4月期间，印度古吉拉特邦中部两处乡村淡水湿地生境中泽鳄（Marsh Crocodile, Crocodylus palustris Lesson, 1831，以下简称MC）的种群动态与行为模式。研究共设置4个采样点（样地I）与2个监测站（样地II），以明确泽鳄的种群数量、行为模式及其与水文化学特征相关的粪便分析结果。本研究开展前，提出了关于水质对泽鳄物种丰富度影响的研究假设。研究结果显示，样地I内泽鳄的种群数量以3号采样点最高（60只），依次为1号采样点（34只）、4号采样点（32只）与2号采样点（12只），总样本量N=138。泽鳄的行为模式以漂浮行为最为频繁（71次），其次为晒背行为（40次）与游泳行为（19次），总有效观测数N=130，占比94.20%。样地II的泽鳄种群峰值出现在2号监测站（75只），其次为1号监测站（53只），总样本量N=128；该生境中泽鳄的行为模式以晒背行为最为显著（75次），依次为漂浮行为（24次）与打哈欠行为（14次），总有效观测数N=113，占比88.28%。相对而言，样地I的物种丰富度（N=138，占比51.88%）高于样地II（N=128，占比48.12%），两地总个体数合计为266只。对比两处观测区域的水文化学参数平均值，两地水温无显著差异（均为18摄氏度）。样地I的pH值、氯化物、磷酸盐与硝酸盐平均浓度均高于样地II，分别为8.41、500.55 mg/L、4.76 mg/L与2.54 mg/L，两者的浓度差值分别为0.71、325.78 mg/L、2.25 mg/L与0.05 mg/L。反之，样地II的水文环境中硫酸盐含量（64.64 mg/L）高于样地I（12.38 mg/L），两者差值为-52.26 mg/L。对样地I的水文化学参数与泽鳄物种丰富度的相关性分析显示，泽鳄种群数量与硝酸盐含量呈显著正相关（相关系数0.929），与磷酸盐含量呈负相关（相关系数0.182）。而在样地II中，pH值对泽鳄物种丰富度的影响更为显著（相关系数1.293），水温的影响相对较弱（相关系数0.563）。本研究结果充分验证了初始提出的“水质对泽鳄物种丰富度具有影响”的研究假设。泽鳄粪便分析结果显示，其粪便中总有机质（Total Organic Matter, TOM）与总有机碳（Total Organic Carbon, TOC）含量最高，分别为366.35%与212.50%，其次为硝酸盐（1.990 mg/gm）、硫（0.314 mg/gm）与磷（0.014 mg/gm）。基于上述研究结果，建议从生态管理视角出发，通过添加选择性富集因子（如硝酸盐与pH值）维持两处研究淡水湿地生境的水质，并落实相关干预措施。此外，由于鳄类粪便富含有机质与有机碳，当地农户可将其商业化利用（综合考量成本收益因素），以提升目标作物的土壤肥力与产量。上述建议将成为保护印度古吉拉特邦中部泽鳄现有种群的有效辅助手段。