Chinese giant salamanders 377
TABLE 2 Results of two-tailed Mann−Whitney U tests comparing recorded water parameter values between grouped sets of sites:
(1) sites where giant salamanders were directly detected during sur- veys vs sites where salamanders were not detected; and (2) sites where giant salamanders were detected during surveys and/or where mean reported last-sighting date was within the previous 5 years vs sites where giant salamanders were not detected and where mean reported last-sighting date was .5 years ago.
Site grouping Parameter Uz P 1
Temperature Dissolved O2
Salinity pH
Ammonia Nitrite Nitrate
Alkalinity dKH
Flow rate 2
Temperature Dissolved O2
Salinity pH
Ammonia Nitrite Nitrate
Alkalinity dKH
Flow rate 173.5
206.5 232.5 215.0
190.0
430.0 298.5 337.0 435.0
319.5 313.5
183.5 −0.783 0.435 135.5
185.5 −0.751 0.453 197.0
0.945 0.347 1.558 0.119
0.412 0.682 0.008 0.992 0.274 0.787
0.565 0.569 0.678 0.497
201.0 −0.465 0.646 392.5
0.498 0.617 0.053 0.960 1.613 0.107 1.157 0.246 0.006 0.992
400.5 −0.403 0.689 377.0 −0.682 0.497
1.364 0.174 1.436 0.150
349.5 −0.960 0.337
explained by PC1 (eigenvalue = 1.67), which had a strong loading for nitrate. PC2 had strong factor loadings for temperature, and explained 22.51% of the variance (eigenvalue = 0.65). PC3 had strong factor loadings for dKH, and explained 19.88%of the variance (eigenvalue = 0.58). Sites where giant salamanders had recently been detected did not cluster separately from sites where they had not recently been detected (Fig. 2a). PCA of water parameters across sites grouped by river
basin (Table 4) revealed that most of the variance (87.62%) was explained by PC1 (eigenvalue = 177.38), which had a strong loading for nitrate. PC2 had a strong loading for temperature, but explained just 6.63% of the variance (eigenvalue = 13.42). Different river basins did not form separate clusters (Fig. 2b), although only a small number of samples were collected from the Yellow River basin.
Discussion
Our multi-year survey effort to detect Chinese giant sala- manders provides a new baseline both for assessing the current status of giant salamander populations across China (Turvey et al., 2018), and also for identifying the likely drivers of their decline, knowledge of which is essential to
TABLE 3 Rotated factor loadings of principal component analysis of water parameters between sites grouped into three categories: (1) sites where giant salamanderswere detected directly during sur- veys; (2) sites where giant salamanders were not detected directly, but with mean last-sighting date within the previous 5 years; and (3) sites where giant salamanders were not detected directly, and with mean last-sighting date.5 years ago. Factor loadings.0.50 are highlighted in bold.
Parameter
Temperature Dissolved O2
Salinity pH
Ammonia Nitrite Nitrate
Alkalinity dKH
Flow rate PC 1
0.268320 0.012662 0.018403 0.053618 0.001699 0.001480 0.731140 0.190040 0.587320
−0.094860 PC 2
−0.792800 0.388930
−0.010620 0.152400
0.000554 0.182130
−0.024350 0.102240
0.295780 −0.255260 PC 3
−0.010920 0.218570
0.030002 0.588620 0.000690 0.073542 0.470670
−0.207320 −0.577950 −0.028040
inform effective conservation management interventions. To investigate possible drivers of giant salamander decline, we explored associations between environmental factors and indicators of potential species presence across our sur- vey sites. These indicators comprised both direct detection of Chinese giant salamanders and metrics of their possible presence based on sighting histories reported by local re- spondents, and local knowledge of exploitation. We chose to assess a range of indicators of giant salamander presence, to minimize the effect of potential error (either commission or omission error) in any specific signal. In addition, mean reported last-sighting date is more robust to error associated with factors such as misidentification or poor recall by non- trained respondents, compared to metrics that are more de- pendent upon single sighting accounts (cf. Hermoso et al., 2013; Turvey et al., 2015). We found no significant differences in any of the water
quality parameters that we tested between sites with no recent signal of giant salamanders, and those with either a direct signal (our detection) or a recent indirect signal (local respondent reports). Our PCA analyses are congruent with these findings, as siteswhere giant salamanderswere de- tected either directly or indirectly do not cluster separately from other sites. This lack of any statistical differences sug- gests that water quality is still suitable for giant salamanders at the survey sites where the species was not detected. This conclusion is supported by the fact that we encountered di- verse amphibian species assemblages, often including other aquatic salamanders, at most survey sites, which typically included amphibian genera known to be primarily associ- ated with large intact forest patches and/or clear streams (e.g. Leptobrachium, Megophrys;Dring, 1979;Malkmus et al., 2002; Bickford et al., 2010) or that are threatened by water
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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