stable isotope analysis

Conservation programmes aiming to suppress or remove invasive small mammal populations that threaten endemic fauna assume that eliminating an individual predator has the same effect as eliminating a conspecific in terms of decreasing risk to the prey species. However, marked between-individual variation in prey take could, at times, lead to uneven predation pressure. Such variation in the diets of introduced predators has long been hypothesised in New Zealand, suggesting that some observed rates of predation are not typical of the prey population as a whole.

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.

Foraging strategies of penguin species can vary according to the quality of the marine environment, and this influences their abundance and breeding success. Little blue penguins (Eudyptula minor) are considered a candidate species for assessing near-shore marine productivity due to their usually limited foraging ranges and reliance on local resources, particularly while rearing chicks.