Search

House mice are among the most widely distributed mammals in the world, and adversely affect a wide range of indigenous biota. Suppressing mouse populations, however, is difficult and expensive. Cost-effective suppression requires knowing how low to reduce mouse numbers to achieve biodiversity outcomes, but these targets are usually unknown or not based on evidence. We derived density-impact functions (DIFs) for mice and small indigenous fauna in a tussock grass/shrubland ecosystem. We related two indices of mouse abundance to five indices of indigenous lizard and invertebrate abundance measured inside and outside mammal-resistant fences. Eight of 22 DIFs were significantly non-linear, with positive responses of skinks (Oligosoma maccanni, O. polychroma) and ground wētā (Hemiandrus spp.) only where mice were not detected or scarce (Woodworthia spp.) were rarely detected where mice were present. A further 9 DIFs were not differentiated from null models, but patterns were consistent with impacts at 5% mouse abundance. This study suggests that unless mouse control programmes commit to very low abundances, they risk little return for effort. Impact studies of invasive house mice are largely restricted to island ecosystems. Studies need to be extended to other ecosystems and species to confirm the universality or otherwise of these highly non-linear DIFs.

Indigenous peoples’ relationships with biodiversity are often poorly recognised in conservation decision-making, but are critical to Indigenous identity and lifeways. These relationships extend to introduced species that are rarely protected under legislation. Kiore (Rattus exulans, Pacific rat) is a species introduced to Aotearoa New Zealand (hereafter Aotearoa) by Māori (the Indigenous people of Aotearoa) as a food source and bio-indicator of ecosystem state. Once common, kiore are now restricted in numbers and range, and widely considered an unwanted organism by conservation managers and some Māori. However, tribal group Ngātiwai wish to safeguard cultural access to remaining kiore on Mauitaha Island. Therefore, the goals of our study were to assess body condition and the reproductive and disease status of kiore on Mauitaha. Of 16 kiore caught, body condition based on body length to mass ratio was similar to that recorded on other islands in Aotearoa. Subcutaneous fat levels were moderate, but lower in individuals with disease inflammation. The results suggest satisfactory population health, but regular monitoring to identify temporal trends in kiore abundance and condition is important for cultural harvesting and long-term population survival. Planning for harvesting by future generations requires transforming conservation biology through Indigenous perspectives, through further assessment of methods, management and agency, examining how Indigenous knowledge and conventional science can be used to balance ecological and cultural trade-offs. Further consideration of ecological habitat and risk is also required for kiore, because the reserve is a single small island, and national conservation priorities focus on native species protection in ecosystems that exclude humans.

Kiore (Pacific rat; Rattus exulans) is both a target for eradication and a taonga or highly valued species in New Zealand, and its abundance and distribution vary considerably throughout the countr...

In the Ross Sea region, most South Polar Skuas (Stercorarius maccormicki) nest near Adelie Penguin (Pygoscelis adeliae) colonies, preying and scavenging on fish, penguins, and other carrion. To derive a relationship to predict skua numbers from better-quantified penguin numbers, we used distance sampling to estimate breeding skua numbers within 1000 m of 5 penguin nesting locations (Cape Crozier, Cape Royds, and 3 Cape Bird locations) on Ross Island in 3 consecutive years. Estimated numbers of skua breeding pairs were highest at Cape Crozier (270,000 penguin pairs; 1099 and 1347 skua pairs in 2 respective years) and lowest at Cape Royds (3000 penguin pairs; 45 skua pairs). The log–log linear relationship (R 2 = 0.98) between pairs of skuas and penguins was highly significant, and most historical estimates of skua and penguin numbers in the Ross Sea were within 95 % prediction intervals of the regression. Applying our regression model to current Adelie Penguin colony sizes at 23 western Ross Sea locations predicted that 4635 pairs of skuas now breed within 1000 m of penguin colonies in the Ross Island metapopulation (including Beaufort Island) and northern Victoria Land. We estimate, using published skua estimates for elsewhere in Antarctica, that the Ross Sea South Polar Skua population comprises ~50 % of the world total, although this may be an overestimate because of incomplete data elsewhere. To improve predictions and enable measurement of future skua population change, we recommend additional South Polar Skua surveys using consistent distance-sampling methods at penguin colonies of a range of sizes.

Cities and urban processes typically have a negative impact on biodiversity via land cover change, high rates of disturbance and high densities of pest species. Increasingly, however, people are being encouraged and empowered to reduce these impacts through urban restoration and backyard conservation initiatives. Internationally, lizards are a common feature of urban biodiversity, but in New Zealand where many species are threatened, little is known about populations of native skinks and geckos in cities. Yet cities may offer unique opportunities for lizard conservation compared with alternatively modified habitats. To explore the potential of cities for the conservation of lizards, we collated knowledge about the current lizard faunas of six New Zealand cities and developed a list of species that would likely have been present in the locations of these cities prior to human settlement. Comparing the two, we found that, although each of the cities has at least one currently urban-dwelling species, the diversity of lizards in all of the cities has declined dramatically since human colonisation. Patterns of species loss in cities reflect those observed across New Zealand more generally; that is, the loss of large-bodied skinks and geckos, probably resulting from predation by introduced mammalian predators, as well as the loss of regionally endemic species. The high diversity of species that are currently, or were historically, present in the locations of New Zealand cities means that urban restoration involving recovery or reintroduction of populations could have significant benefits for lizard conservation and advocacy.