Estimating the proportion of Archey’s frogs in the Wharekirauponga mine vibration footprint 15 Population Estimates for Archey’s Frog Published Population Estimates The only published estimate of the total Archey’s frog population is 5,000–20,000 mature individuals[1, 27, 28] in the entire NZ population. The estimate was made some years after the chytrid induced population crash and presumed recovery[12] and was published in both the NZ Native Frog Recovery Plan[1] and two reports on the conservation status of NZ frogs[27, 28]. There is no explanation for how the total population estimate was arrived at. The total estimate seems implausible and is not consistent with information on frog densities and distribution available at the time[8, 12, 13, 29]. It seems likely that the total population estimate was selected to fit the D(1/1) status criteria for Nationally Vulnerable taxa (i.e. 5,000–20,000 mature individuals) in NZ’s species threat ranking system[30]. In the most recent revision of Archey’s frog’s threat ranking status to At Risk-Declining, the status criteria A(1) is again a population of 5,000–20,000 mature individuals[28]. The Conservation Status Assessment for Archey’s frog on the New Zealand Threat Classification System website (https://nztcs.org.nz/assessments) incorrectly cites the 2018 report on the conservation status of NZ frogs[28] as providing a population estimate of 20,000–100,000 mature individuals. Estimating the Size of the Archey’s Frog Population on the Coromandel Population Estimates of the number of Archey’s frogs in the 578 km2 of suitable habitat ≥200 m a.s.l. along the axial range of the Coromandel Peninsula were derived using frog density estimates obtained from capture-recapture surveys and nocturnal plot surveys undertaken during the last four years (Table 9). The data provides density estimates for seven habitat types, with duplicate estimates for one habitat: low altitude (200–500 m a.s.l.) manuka-kanuka scrub. Population estimates for each of the seven habitat types with density estimates were obtained by multiplying density estimates for the habitat type by the area of the habitat present within the 578 km2 of frog habitat (Table 9). Dominant vegetation type alone is not always a good predictor of frog density, as altitude and secondary vegetation types both affect frog density in some of the dominant vegetation types. Altitude had a large effect on density estimates for both manuka-kanuka scrub and lowland podocarp-hardwood forest (Table 8), with much higher densities at lower altitudes in manuka-kanuka scrub (928 c.f. 38) and at higher altitudes in lowland podocarp-hardwood forest (1,902 ha-1 c.f. 581 ha-1). Areas dominated by kauri forest, but including lowland podocarp-hardwood forest (i.e. N2, n3a), had much higher density estimates than areas of kauri forest with other secondary components (994 ha-1 c.f. 224 ha-1). Both of these effects are also apparent in the pattern of Archey’s frog records in the Amphibian & Reptile Distribution Scheme (Figure 4b). Consequently, for population estimation, the three vegetation types (M1, N2, and N3a) were split into six habitats: manuka-kanuka scrub (M1) at low altitudes (200–500 m a.s.l.) and higher altitudes (≥500 m a.s.l.); podocarp-hardwood forest (N3a) at low altitudes (200–500 m a.s.l.) and higher altitudes (≥500 m a.s.l.); and kauri forest with (N2, n3a) and without (N2, ...) podocarp-hardwood forest.
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