Microhabitat selection characteristics and conservation implications of the Chinese crocodile lizard (Shinisaurus crocodilurus)

doi:10.17520/biods.2025203

Abstract

Abstract:

Aim: Identifying the microhabitat selection characteristics of endangered species is essential for developing effective conservation strategies. The Chinese crocodile lizard (Shinisaurus crocodilurus) is a globally endangered species, with fewer than 1,500 individuals remaining in the wild. This study aimed to systematically analyze the influence of various microhabitat variables on the microhabitat selection of Chinese crocodile lizards.

Methods: We carried out microhabitat quadrat investigations in the stream environments where Chinese crocodile lizards are distributed within the Guangdong Luokeng Crocodile Lizard National Nature Reserve. We used random forest model and generalized linear mixed model (GLMM) to assess the key microhabitat variables that determined the occurrence of Chinese crocodile lizards.

Results: Random forest analysis revealed that perch density, stream depth, stream sand coverage percentage, canopy closure, stream velocity, and stream width were the critical microhabitat variables affecting the occurrence of Chinese crocodile lizards, each with specific ecological thresholds. The final GLMM indicated that perch density, stream depth, canopy closure, and stream width all exhibited significant positive associations with the occurrence probability of the Chinese crocodile lizard. Among these variables, perch density was identified as the primary influencing factor, followed by stream depth. Despite its modest independent contribution, canopy closure served as an indispensable underlying factor, whereas stream width was determined to be a marginal factor, exerting a limited effect.

Conclusion: Our study highlights that improving perch density should be prioritized in the conservation of Chinese crocodile lizards. Simultaneously, measures such as improving the hydrological environment and optimizing canopy closure should be implemented to provide more suitable microhabitats for the population. These findings contribute to a better understanding of the microhabitat requirements of Chinese crocodile lizards and provide scientific basis for targeted conservation actions.

Key words: microhabitat selection, random forest model, generalized linear mixed model, perch density, Chinese crocodile lizard

Junhan Shen, Haiyang Gao, Song Sun, Fei Wu, Nan He, He Wang, Yan Hua, Zhengjun Wu. Microhabitat selection characteristics and conservation implications of the Chinese crocodile lizard (Shinisaurus crocodilurus)[J]. Biodiv Sci, 2025, 33(11): 25203.

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URL: https://www.biodiversity-science.net/EN/10.17520/biods.2025203

https://www.biodiversity-science.net/EN/Y2025/V33/I11/25203

Figures/Tables 7

References 52

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变量名 Variable		变量介绍 Variable introduction	测量方法 Measurement methods	平均值 Mean	中位数 Median		标准差 SD		频数 Frequency
连续变量 Continuous variables
树冠层高度 Canopy height (m)		从地面至乔木树冠顶部的垂直距离 Vertical height from the ground level to the top of the tree canopy	采用2 m标准枝杆作为视觉参照标尺进行目测估算 Visual estimation was performed using a 2-meter standard branch pole as a visual reference scale	8.93	8.10		3.65		-
灌木层高度 Shrub layer height (cm)		从地面至灌木层顶部的垂直距离 Vertical height from the ground to the top of the shrub layer	利用钢卷尺测量样方内5个随机选择的灌木斑块的高度, 并计算其平均值 The height of five randomly selected woody patches within the quadrat was measured using a measuring tape, and the average value was calculated	84.70	77.00		36.70		-
郁闭度 Canopy closure (%)		林冠层枝叶垂直投影面积占林地总面积的比例 Canopy cover percentage	通过测量样方内4个角点及中心点的垂直冠层投影面积与样方总面积的比值, 并计算5个测量点的平均值来确定 It was determined by measuring the ratio of the vertical canopy projection area to the total quadrat area at the four corners and the center point within the quadrat, and then calculating the mean value from these five measurement points	52.90	52.60		16.20		-
溪流深度 Stream depth (cm)		溪流的平均深度 Mean depth of the stream	在每个样方的上、中、下部测量, 包括最大/最小宽度和深度, 最终计算平均值 Measurements of maximum/minimum width and depth were taken at the upper, middle, and lower sections of each quadrat, with the mean values subsequently calculated	19.30	17.10		9.77		-
溪流宽度 Stream width (cm)		溪流的平均宽度 Mean width of the stream		151.00	143.00		56.00		-
溪流流速 Stream velocity (cm/s)		溪流的平均流速 Mean flow velocity of the stream	采用LS300-A型便携式流速仪测定样方上、中、下游的表面流速(cm/s), 测定值经算术平均与对数转换后用于统计分析 Surface flow velocity (cm/s) at the upstream, midstream, and downstream sections of the quadrat was measured using a portable LS300-A current meter. The measured values were arithmetically averaged and log-transformed for statistical analysis	24.60	26.40		14.40		-
溪沟壁坡度 Gully bank slope (°)		溪流两侧土坡或石壁的坡度 Streambank slope	采用坡度仪测量样方上部、中部和下部的两侧溪沟壁坡度, 计算平均值 The gradient of both streambanks at the upper, middle, and lower sections of the quadrat was measured using a clinometer, and the mean value was calculated	46.30	48.20		18.10		-
溪沟坡度 Gully slope (°)		样方沿溪流的整体坡度 Overall longitudinal slope of the quadrat along the stream	使用坡度计测量样方的4个角点和中心位置, 共5个点, 计算所得数据的平均值 The mean value was calculated from measurements taken with a clinometer at five locations: the four corners and the center of the quadrat	8.72	7.67		6.42		-
溪沟坡向 Gully aspect (°)		溪流流向的朝向 Flow direction azimuth	使用罗盘(0-360°)进行测量。为处理统计分析中的循环特性, 将数据进行正弦变换处理 Measured using a compass (0-360°). To address the circular nature of the data in statistical analysis, the values were transformed using a sine transformation	-0.34	-0.84		2.71		-
溪流沙覆盖比 Stream sand coverage percentage (%)		溪流中沙在基质表面的覆盖比例 Percent sand cover on the streambed	基于溪流宽度测量数据, 构建样地俯视平面图。将样方划分为0.5 m × 0.5 m的单元网格, 基于目视判读记录各网格属性参数, 通过网格法定量测算溪流沙质基底覆盖率、灌草盖度及溪流面积(关法春等, 2010) Based on the stream width measurement data, an overhead schematic diagram of the sampling site was constructed. The quadrat was divided into 0.5 m × 0.5 m unit grids, and attribute parameters for each grid were recorded based on visual interpretation. Using the grid-based method, quantitative calculations were performed to determine the coverage of sandy substrate, shrub and herb cover, and stream surface area (Guan et al, 2010)	59.20	57.80		22.90		-
灌草盖度 Shrub and herb coverage (%)		灌木层与草本层植被的垂直投影面积占样方内陆地总面积的百分比 Percent shrub and herb cover		43.70	43.40		19.00		-
溪流面积 Stream area (m²)		溪流的面积 Area of stream		6.67	6.20		2.94		-
栖枝密度 Perch density (unit/m²)		溪流水面上每平方米有多少根可供鳄蜥栖息使用的树枝 Density of branches suitable for Chinese crocodile lizard perching per square meter of stream water surface	统计被认为是鳄蜥可用的悬垂于水面的栖枝数量(罗树毅等, 2021), 并按溪流面积进行了标准化处理 The number of overhanging branches deemed available for the Chinese crocodile lizard was quantified (Luo et al, 2021) and standardized by the stream surface area	0.86	0.71		0.90		-
逻辑变量 Logical variables
回水塘有无 Backwater pond existence	有 Yes (1)	样方里有没有小池塘 Presence of small ponds within the quadrat	通过直接观察将其分类为1 (存在)或0 (不存在) It was categorized as 1 (present) or 0 (absent) through direct observation	-		-		-	156
回水塘有无 Backwater pond existence	无 No (0)	样方里有没有小池塘 Presence of small ponds within the quadrat		-		-		-	80
字符变量 Character variables
林型 Forest type	常绿阔叶林 Evergreen broad-leaved forest	植被类型 Vegetation type	依据实地评估, 将其归类为常绿阔叶林或竹林 It was classified as either evergreen broad-leaved forest or bamboo forest based on field assessment	-		-		-	170
林型 Forest type	竹林 Bamboo forest	植被类型 Vegetation type		-		-		-	66

变量名 Variable		变量介绍 Variable introduction	测量方法 Measurement methods	平均值 Mean	中位数 Median		标准差 SD		频数 Frequency
连续变量 Continuous variables
树冠层高度 Canopy height (m)		从地面至乔木树冠顶部的垂直距离 Vertical height from the ground level to the top of the tree canopy	采用2 m标准枝杆作为视觉参照标尺进行目测估算 Visual estimation was performed using a 2-meter standard branch pole as a visual reference scale	8.93	8.10		3.65		-
灌木层高度 Shrub layer height (cm)		从地面至灌木层顶部的垂直距离 Vertical height from the ground to the top of the shrub layer	利用钢卷尺测量样方内5个随机选择的灌木斑块的高度, 并计算其平均值 The height of five randomly selected woody patches within the quadrat was measured using a measuring tape, and the average value was calculated	84.70	77.00		36.70		-
郁闭度 Canopy closure (%)		林冠层枝叶垂直投影面积占林地总面积的比例 Canopy cover percentage	通过测量样方内4个角点及中心点的垂直冠层投影面积与样方总面积的比值, 并计算5个测量点的平均值来确定 It was determined by measuring the ratio of the vertical canopy projection area to the total quadrat area at the four corners and the center point within the quadrat, and then calculating the mean value from these five measurement points	52.90	52.60		16.20		-
溪流深度 Stream depth (cm)		溪流的平均深度 Mean depth of the stream	在每个样方的上、中、下部测量, 包括最大/最小宽度和深度, 最终计算平均值 Measurements of maximum/minimum width and depth were taken at the upper, middle, and lower sections of each quadrat, with the mean values subsequently calculated	19.30	17.10		9.77		-
溪流宽度 Stream width (cm)		溪流的平均宽度 Mean width of the stream		151.00	143.00		56.00		-
溪流流速 Stream velocity (cm/s)		溪流的平均流速 Mean flow velocity of the stream	采用LS300-A型便携式流速仪测定样方上、中、下游的表面流速(cm/s), 测定值经算术平均与对数转换后用于统计分析 Surface flow velocity (cm/s) at the upstream, midstream, and downstream sections of the quadrat was measured using a portable LS300-A current meter. The measured values were arithmetically averaged and log-transformed for statistical analysis	24.60	26.40		14.40		-
溪沟壁坡度 Gully bank slope (°)		溪流两侧土坡或石壁的坡度 Streambank slope	采用坡度仪测量样方上部、中部和下部的两侧溪沟壁坡度, 计算平均值 The gradient of both streambanks at the upper, middle, and lower sections of the quadrat was measured using a clinometer, and the mean value was calculated	46.30	48.20		18.10		-
溪沟坡度 Gully slope (°)		样方沿溪流的整体坡度 Overall longitudinal slope of the quadrat along the stream	使用坡度计测量样方的4个角点和中心位置, 共5个点, 计算所得数据的平均值 The mean value was calculated from measurements taken with a clinometer at five locations: the four corners and the center of the quadrat	8.72	7.67		6.42		-
溪沟坡向 Gully aspect (°)		溪流流向的朝向 Flow direction azimuth	使用罗盘(0-360°)进行测量。为处理统计分析中的循环特性, 将数据进行正弦变换处理 Measured using a compass (0-360°). To address the circular nature of the data in statistical analysis, the values were transformed using a sine transformation	-0.34	-0.84		2.71		-
溪流沙覆盖比 Stream sand coverage percentage (%)		溪流中沙在基质表面的覆盖比例 Percent sand cover on the streambed	基于溪流宽度测量数据, 构建样地俯视平面图。将样方划分为0.5 m × 0.5 m的单元网格, 基于目视判读记录各网格属性参数, 通过网格法定量测算溪流沙质基底覆盖率、灌草盖度及溪流面积(关法春等, 2010) Based on the stream width measurement data, an overhead schematic diagram of the sampling site was constructed. The quadrat was divided into 0.5 m × 0.5 m unit grids, and attribute parameters for each grid were recorded based on visual interpretation. Using the grid-based method, quantitative calculations were performed to determine the coverage of sandy substrate, shrub and herb cover, and stream surface area (Guan et al, 2010)	59.20	57.80		22.90		-
灌草盖度 Shrub and herb coverage (%)		灌木层与草本层植被的垂直投影面积占样方内陆地总面积的百分比 Percent shrub and herb cover		43.70	43.40		19.00		-
溪流面积 Stream area (m²)		溪流的面积 Area of stream		6.67	6.20		2.94		-
栖枝密度 Perch density (unit/m²)		溪流水面上每平方米有多少根可供鳄蜥栖息使用的树枝 Density of branches suitable for Chinese crocodile lizard perching per square meter of stream water surface	统计被认为是鳄蜥可用的悬垂于水面的栖枝数量(罗树毅等, 2021), 并按溪流面积进行了标准化处理 The number of overhanging branches deemed available for the Chinese crocodile lizard was quantified (Luo et al, 2021) and standardized by the stream surface area	0.86	0.71		0.90		-
逻辑变量 Logical variables
回水塘有无 Backwater pond existence	有 Yes (1)	样方里有没有小池塘 Presence of small ponds within the quadrat	通过直接观察将其分类为1 (存在)或0 (不存在) It was categorized as 1 (present) or 0 (absent) through direct observation	-		-		-	156
回水塘有无 Backwater pond existence	无 No (0)	样方里有没有小池塘 Presence of small ponds within the quadrat		-		-		-	80
字符变量 Character variables
林型 Forest type	常绿阔叶林 Evergreen broad-leaved forest	植被类型 Vegetation type	依据实地评估, 将其归类为常绿阔叶林或竹林 It was classified as either evergreen broad-leaved forest or bamboo forest based on field assessment	-		-		-	170
林型 Forest type	竹林 Bamboo forest	植被类型 Vegetation type		-		-		-	66

变量名 Variable	平均效应值 β_avg	标准误 SE	Z	P
截距 Intercept	-6.322	1.007	-6.280	3.39e-10^***
栖枝密度 Perch density (PD)	1.906	0.315	6.052	1.43e-09^***
溪流深度 Stream depth (SD)	0.114	0.025	4.497	6.89e-06^***
郁闭度 Canopy closure (CC)	0.031	0.011	2.880	0.004^**
溪流宽度 Stream width (SW)	0.008	0.004	2.080	0.038^*

变量名 Variable	平均效应值 β_avg	标准误 SE	Z	P
截距 Intercept	-6.322	1.007	-6.280	3.39e-10^***
栖枝密度 Perch density (PD)	1.906	0.315	6.052	1.43e-09^***
溪流深度 Stream depth (SD)	0.114	0.025	4.497	6.89e-06^***
郁闭度 Canopy closure (CC)	0.031	0.011	2.880	0.004^**
溪流宽度 Stream width (SW)	0.008	0.004	2.080	0.038^*

变量名 Variable	平均效应值 β_avg	标准误 SE	置信区间下限 CI_Low	置信区间上限 CI_High	相对重要性 Relative importance (RI)	P
截距 Intercept	-6.432	1.148	-8.692	-4.172		< 0.001
栖枝密度 Perch density (PD)	1.825	0.324	1.190	2.460	1.000	< 0.001
溪流深度 Stream depth (SD)	0.120	0.027	0.068	0.172	1.000	< 0.001
郁闭度 Canopy closure (CC)	0.031	0.011	0.009	0.053	1.000	0.005
溪流宽度 Stream width (SW)	0.008	0.004	-0.001	0.016	0.747	0.051
溪流沙覆盖比 Stream sand coverage percentage (SSCP)	0.011	0.008	-0.005	0.027	0.506	0.160
溪流流速 Stream velocity (SV)	0.144	0.161	-0.172	0.459	0.315	0.372