378 B. Tapley et al.


FIG. 2 Scatterplots of first and second principal components from principal component analyses of water parameters between sites, grouped by (a) giant salamander detection history, and (b) river basin. Shaded areas are the smallest convex polygons that enclose all the points in each grouped data set.


pollution (e.g. Batrachuperus, Paramesotriton; Fei&Ye, 2004; Gu et al., 2004;Zhao&Yuan, 2004). Some freshwater landscapes with historical records of


Chinese giant salamanders, including the type locality for Andrias davidianus in Zhongba, Sichuan, are now heavily degraded as a result of industrial, agricultural and other an- thropogenic activities, and are unable to support giant sala- mander populations (Dai et al., 2009). Habitat suitability modelling based on available environmental parameters, however, suggests that considerable suitable habitat for giant salamanders still exists across China (Chen et al., 2018). Our analyses of water quality parameters at a large number of sites containing such apparently suitable habitat


TABLE 4 Rotated factor loadings of principal component analysis of water parameters from sites grouped by river basin (Yangtze, Yellow, Pearl, and south-east rivers). Factor loadings .0.50 are highlighted in bold.


PC 1


Temperature Dissolved O2


Salinity pH


Ammonia Nitrite Nitrate


Alkalinity dKH


Flow rate


−0.626430 0.029247


0.014405 0.074968 0.001651


−0.011740 0.160870


0.254010 0.714360


−0.006710 PC 2


0.203710 0.031494 0.014093 0.006203 0.006861 0.044073 0.972960


−0.038540 −0.029020 −0.079450


PC 3 0.704200


−0.204530 0.019000


0.040411 0.025306 0.149210


−0.139530 0.182090


0.588490 −0.196040


did not reveal any environmental differences between sites with and without giant salamanders, further validating the habitat suitability model developed by Chen et al. (2018). Because of the ambitious scale of this study, water samples were collected only once at each site, and our surveys were undertaken during May–October over a 3-year period. Both temperature and nitrate accounted for much of the variance between sites in some of the PCA analyses. Temperature and nitrate are likely to vary between seasons, with nitrate increasing after periods of heavy rainfall (e.g. Zhu et al., 2009).Werecommend that future assessment of water qual- ity should analyse multiple water samples, with data col- lected at the same time of year across survey sites if possible. Habitat loss and degradation remains a threat to giant salamander populations across China, and we did not inves- tigate water pollutants such as heavy metals, phosphates or persistent organic pollutants, which are likely to affect giant salamanders and other amphibians (Dai et al., 2009). However, the results of our large-scale multi-year survey suggest that habitat loss is not the main driver of giant sala- mander population decline in China. Principal component analysis of water parameters between river basins demon- strates a high degree of similarity and there was overlap in principal components 1 and 2. Our results support the hy- pothesis that illegal overexploitation is an important driver of giant salamander decline in areas where suitable habitat remains. A substantial proportion of local respondents re- ported that hunting was amajor threat to giant salamanders, and at least one respondent from each of nearly half of the


Oryx, 2021, 55(3), 373–381 © The Author(s), 2021. Published by Cambridge University Press on behalf of Fauna & Flora International doi:10.1017/S0030605320000411


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