Estimating the proportion of Archey’s frogs in the Wharekirauponga mine vibration footprint 11 Table 6. Total population and density (ha-1) estimates from re-analysis of data from Hotham (2019), with plots combined. The 24 plots in the Wharekirauponga (WKP) catchment were all in the ≥2 mm sec-1 vibration footprint. To obtain an estimate for the M1, n5 vegetation type, two plots located in the N2, n3a vegetation type were removed leaving 22 plots. N. Ind. is the number of uniquely identified individuals in the plots. NZ LRI Veg. Type N. Plots N. Ind. N. of Frogs in the Plots Density Estimate (ha-1) Site N. SE CI95% ha-1 SE CI95% WKP M1,n5 & N2,n3a 24 150 221 ±34 (154–288) 920 ±142 (643–1,198) WKP M1, n5 22 144 204 ±29 (148–261) 929 ±131 (643–1,186) Mahakirau N5, N2 16 27 33 ±5.8 (21–44) 408 ±73 (265–550) The twenty-four Wharekirauponga plots were between 120 m and 350 m a.s.l., while the eight Mahakirau plots were between 300 m and 460 m a.s.l.. Twenty-two of the twenty-four Wharekirauponga plots were in NZ LRI vegetation type manuka-kanuka scrub, with general hardwood (M1, n5). The other two plots were in kauri forest with lowland podocarphardwood forest (N2, n3a). The eight Mahakirau plots were all in general hardwood and kauri forest (N5, N2). I re-analysed the capture-recapture data using log-linear capture-recapture modelling[16, 17] with the function closedp.t in the R-package Rcapture to obtain estimates of numbers of frogs present on the plots and average population densities at the two sites. Population estimates were obtained separately for the two sites by pooling data from all plots at each of the sites. To obtain population estimate for frogs in manuka-kanuka scrub, with general hardwood (M1, n5), data from the Wharekirauponga were re-analysed without data from a pair of plots in the kauri forest with lowland podocarp-hardwood forest (N2, n3a). The best fitting model in all three analyses included a behavioural effect (i.e. learned capture avoidance). Models without a behavioural effect were all poor fits (Table 13, Appendix). The best-fit capture-recapture population estimates were 221 frogs in the twenty-four Wharekirauponga plots, 204 frogs in the twenty-two manuka-kanuka scrub plots in the Wharekirauponga, and 33 frogs in the eight Mahakirau plots (Tables 6 & 13). For comparison, there were 150, 144 and 27 uniquely identified individual fogs in the three sets of plots respectively. Density estimates for the Wharekirauponga and Mahakirau sites calculated from total plot areas at the sites and total population estimates in the best-fit models were 920 ha-1 (CI95%: 643 –1,198 ha-1) for the Wharekirauponga site and 408 ha-1 (CI95%: 265 – 550 ha-1) for the Mahakirau site (Table 6). The density estimate for frogs in the twenty-two Wharekirauponga plots in manuka-kanuka scrub with general hardwood (vegetation type M1, n5) is 929 ha-1 (CI95%: 643 –1,186 ha-1). Given published information on Archey’s frog distribution, this density estimate is surprisingly high for the vegetation type, engendering concern about the estimate’s quality. Heterogeneity in capture rates can have major effects on capture-recapture population estimates[18]. For instance, low recapture rates caused by learned capture avoidance or temporary absences from a study plot can inflate population estimates. However, in this case there were 144 uniquely identified frogs in the twenty-two plots, giving a minimum density estimate of 655 frogs ha-1, which suggests that the capture-recapture density estimate of 929 ha-1 is not an extreme value. Further support for the estimates comes from the high numbers of Archey’s frogs found in manuka-kanuka
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