predation

The fragmentation of forested environments in Aotearoa | New Zealand has resulted in many small, geographically isolated populations that face an increased risk of extinction. However, population extinction itself, and its proximate causes, are rarely witnessed scientifically. As part of a broader study, we assessed the population status of a remnant kakaruai (South Island robin; Petroica australis) population within the Ōtepoti | Dunedin area.

Cats (Felis catus) are among the most damaging invasive predators in the world, and their impacts in Aotearoa New Zealand (NZ) are particularly severe. However, unlike the invasive predators that are targeted for eradication under the Predator Free NZ initiative, cats are also highly valued by people and therefore will likely remain widespread in NZ for the foreseeable future. This raises the question of how to manage the impacts of cats, which include predation, competition, and disease affecting native species, livestock, and humans.

Predator-free sanctuaries can assist the conservation of multiple endemic species, but quantitative evidence of these benefits is often lacking, especially for herpetofauna. We measured population responses of three common lizard species (schist geckos, Woodworthia ‘Central Otago’; McCann’s skinks, Oligosoma maccanni; and southern grass skinks, O. aff. polychroma Clade 5) 1 year before and 5 years after mammalian predators were removed inside a mammal-proof fence in a dry grass/shrubland habitat with abundant schist rock in Central Otago, New Zealand.

A two-phase translocation of Hamilton's frog (Leiopelma hamiltoni) into Zealandia Ecosanctuary Te Māra a Tāne, in Wellington, was the first attempt to restore the species to the mainland. All non-native mammals had been eradicated there, but house mice (Mus musculus) re-invaded, providing an opportunity to investigate their impact on L. hamiltoni. In Phase I, 60 frogs were translocated into mouse-proof enclosures over 2006–2007.

New Zealand’s native forest bird species with high taxonomic levels of endemism (deep endemics) are more vulnerable to decline than species that arrived and speciated more recently. Here we use national-scale local occupancy data to show that three endemism-linked life-history traits account for greater vulnerability of deep-endemic species in the extant forest avifauna, but also that other, more subtle traits and mechanisms favour rather than hinder endemic persistence.

Kererū declined rapidly following European settlement in New Zealand, and they remain at a reduced density. We assessed three sources of information to test the hypothesis that predation by introduced mammals and abundance of food resources are the two major factors determining kererū abundance across New Zealand. First, we reviewed the literature on factors affecting the vital rates of kererū. This analysis showed that predation is the cause of most nest failures and deaths in kererū.

The alpine zone of New Zealand covers c. 30% of public conservation land and is home to a high diversity of endemic species. Predation by introduced stoats (Mustela erminea) is identified as a major threat to alpine fauna. However, a lack of biological information, such as what stoats eat in different settings, hinders efforts to focus control measures in time and space in order to achieve the greatest conservation gains. We used a biochemical tool, stable isotope analysis, to estimate stoat diet across three time-periods in the alpine zone of three national parks.

Little is known about the impact of aerial 1080 control on nesting success and abundance of birds. The South Island (SI) robin (Petroica australis) is vulnerable to predation by exotic mammals, with declining populations on the east coast of the South Island of New Zealand.

Urbanisation causes fragmentation of natural habitats, which results in loss of biodiversity, while promoting an environment that can facilitate invasive species. However, forest fragments are an important refuge for native species and therefore understanding and mitigating threats in fragments is critical.

Managed pine plantations now constitute a large portion of mainland New Zealand. Despite many native birds inhabiting these exotic habitats, their value for biodiversity conservation is unclear. Although numerous studies have quantified densities of native bird species in pine plantations, it is unknown whether these individuals constitute self-sustaining populations. Here we address this question for North Island robins (Petroica longipes) in a Pinus radiata plantation in the central North Island.