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.本研究旨在调查印度古吉拉特邦中部两处淡水沼泽乡村生境中泽鳄（Marsh Crocodile, Crocodylus palustris Lesson, 1831）的种群动态与行为模式：于2021年1月至4月期间，在样地一的4个采样点及样地二的2个监测站开展研究，以阐明泽鳄（简称MC）的种群数量、行为模式及其与水化学特征相关的粪便分析。本研究启动前，我们提出了关于水质对泽鳄物种丰富度影响的研究假说。 研究结果显示，样地一（总个体数N=138）中，点位3的泽鳄个体数最多，达60只，其次为点位1（34只）、点位4（32只）与点位2（12只）。泽鳄的行为频次以浮水（71次）最高，其次为晒背（40次）与游泳（19次），总有效观测次数为130次，占总观测的94.20%。样地二中，点位2的泽鳄种群峰值达75只，高于点位1的53只（总个体数N=128）；该样地中，泽鳄的行为模式以晒背（75次）最为显著，其次为浮水（24次）与打哈欠（14次），总有效观测次数为113次，占总观测的88.28%。 相较而言，样地一的物种丰富度更高（N=138，占总个体数的51.88%），样地二为（N=128，占比48.12%），两处样地的泽鳄总个体数合计266只。对比两处观测区域的水化学参数平均值，两地水温无显著差异，均为18摄氏度。样地一的pH值、氯化物、磷酸盐与硝酸盐平均浓度均高于样地二，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，样地二的水文环境中硫酸盐含量为64.64 mg/L，高于样地一的12.38 mg/L，两者差值为-52.26 mg/L，差异显著。 对泽鳄物种丰富度与水化学参数的相关性分析显示，样地一中泽鳄种群与硝酸盐含量梯度呈显著正相关（相关系数0.929），与磷酸盐含量呈负相关（相关系数0.182）；而样地二中，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“水质对泽鳄物种丰富度存在影响”的研究假说。泽鳄粪便分析结果显示，粪便中总有机质（TOM）与总有机碳（TOC）含量最高，分别为366.35%与212.50%，其次为硝酸盐（1.990 mg/g）、硫（0.314 mg/g）与磷（0.014 mg/g）。 基于上述研究结果，建议从管理视角出发，通过添加选择性富集因子（如硝酸盐与pH值）维持两处研究样地的淡水沼泽生境水质，并落实相关配套措施。此外，由于鳄类粪便富含有机碳与有机质，当地农户可将其商业化利用（兼顾成本收益），以提升目标作物的土壤肥力与产量。上述建议可作为维持印度古吉拉特邦中部泽鳄现有种群的有效辅助手段。