Effect of pest-management operations on the abundance and size-frequency distribution of the New Zealand endemic frog Leiopelma hochstetteri

In New Zealand, introduced mammals, especially rats, have been considered a primary factor in the extinction of amphibians. Leiopelma hochstetteri is a riparian frog, and is the most widespread of the surviving species of native frogs in New Zealand. At present, all populations of this frog species coexist with introduced mammals, which in some cases have been subject to pest-management operations without monitoring the potential benefits or damage to the frogs. We investigated the influence of a 7-year rat management operation on frog abundance in the Waitakere Ranges, New Zealand. We identified which habitat characteristics had significant influence on frog abundance; confirmed that the study areas represented similar habitats both inside and outside the pest-managed area, and finally evaluated the effects of the pest-management activities. Frog abundance was positively correlated with percentage area covered by boulders and percentage area covered by water. Since the study sites were similar in terms of those variables, we could make a reliable comparison of frog abundance in relation to pest management. Presence/absence of pest-management operations did not have any significant effect on frog abundance. Size-frequency distribution data suggest that there has been recruitment of young frogs both inside and outside pest-management areas in the past 7 years.