4 Boffa Miskell Ltd | Pest Animal Management Plan | Wharekirauponga Compensation Package | 30 May 2022 Baber et al. (2009) suggested that introduced mammals are likely to be the most serious threat to Hochstetter’s frogs (L. hochstetteri), with ship rats (Rattus spp.) in particular named as a primary factor contributing to the extinction of New Zealand’s herpetofauna. Molecular diet analysis has demonstrated that both Hochstetter's and Archey's frogs (L. archeyi) are a food source for rats (Egeter et al., 2015, 2019), with ship rats consuming both species on mainland New Zealand. Rat bite marks have previously been discovered on the remains of Archey’s frogs (Thurley & Bell, 1994). Recent research (Germano in press), demonstrated that the control of rats, and potentially mice, are shown to benefit Archey’s frogs. It is likely other introduced mammalian predators such as mustelids (Mustela sp.) and cats (Felis catus) are also contributing to the decline of native anurans, with multiple observations of predation events (Baber et al., 2008). Feral pigs (Sus scrofa) also destroy frog habitat by trampling and foraging on the edge of streams, and may also opportunistically consume native frogs (Baber et al., 2006). There have now been multiple reported events of native frogs being found in hunted pigs, with anecdotal reports of live Archey’s frogs being found in some (Emily Hotham, Pers comm). It is likely that the impact of feral pigs on frog predation has previously been underestimated, and feral pig control should form a key part of any population restoration attempts. The control of the feral ungulates also promotes an increase in ground cover vegetation (and thereby microhabitat quality), which is also key to promoting population recovery (Easton, 2021). Leaving predators and other pests uncontrolled (or poorly controlled) will lead to ongoing predation events and population declines. Despite this, efforts to control predators for recovery of threatened amphibian populations are few (Baber et al., 2008). Furthermore, whilst undertaking a review of other predator control programmes for frogs as part of establishing the WPAMP, it became clear that previous pest control attempts have generally not been comprehensive and adaptive enough to allow for the potential maximum benefits. 1.5 Benefits of predator control on native frogs Table 2 summarises three comparable case studies that have reported benefits of intensive predator control on Leiopelma frog populations in New Zealand. These case studies show that predator control, in particular targeting rats (either specifically for protection of frogs or other native species), have measurable benefits on both population size and juvenile recruitment of Leiopelma populations. For example, Baber et al. (2008) found that ship rat, stoat and possum control that was carried out to protect kōkako in the Hunua Ranges (Kōkako Management Area; KMA) resulted in an increased abundance of Hochstetter’s frog, as well as a higher proportion of juveniles than compared to nearby areas with substantially lower levels of pest control. Frog abundance was significantly higher within the KMA than in areas outside the KMA that were subject to much lower levels of pest control. In support of our findings, Baber (2006) also found higher relative abundances of frogs inside the KMA than outside. Further, the smaller mean size of frogs and the higher proportion of juveniles within the KMA compared to outside the KMA, indicates that introduced mammals may also influence population structure (M. J. Baber et al., 2008). Pledger (2011, 2013) and Ramirez (2017) also found that Archey’s frog benefited from ship rat control at Whareorino forest (Table 2). Recent reports by DOC (including Easton 2020 and 2021), monitoring L. archeyi at Whareorino, conclude that “it does seem that rat control has been generally effective in suppressing rat numbers and is likely benefiting the frogs”. However, habitat protection for frogs remains challenging at Whareorino (particularly with ongoing ungulate impacts), and rat numbers in frog
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