Tawaki: Trust four year study concludes …

The West Coast Penguin Trust’s four-year study of the threats predators pose to Fiordland crested penguins (tawaki) concludes that control of stoats appears to be required in some years, in some colonies.

In 2016 most tawaki eggs or chicks at Jackson Head were taken by stoats, a marked contrast to none most seasons or at worst just one or two killed by stoats other years at Jacksons and at our second study colony at Gorge River. The reason for the high level of stoat predation at Jackson Head in 2016 is believed to be a mast event in the nearby beech forests when vast quantities of seed were produced enabling a huge increase in rat and stoat numbers.

During the 2016 season (August to October) the egg or chick at nine of the ten nests monitored by our motion activated cameras was killed and stoats were recorded more frequently that season (50 observations compared to just one in 2014, 10 in 2015 and 2-3 in 2017). Our Tawaki Coalition partner, The Tawaki Project, led by Dr Thomas Mattern, reported almost complete breeding failure at Jackson Head in 2016 with only three chicks surviving in the entire colony, and then only after urgent stoat trapping.

There was also near total breeding failure at Jackson Head in 2015. Between mid-September and early October many nests failed but that year the chicks starved. It appeared that the El Niño conditions (i.e. prevailing southerly winds) caused low productivity, thus limited food being available within foraging range of the colony that year.

In contrast to the near total breeding failure at Jackson Head in 2016, anecdotal observations indicated there had been good breeding success at a colony about 70 km away in an area with landscape level predator control using 1080. In 2017 we extended operations to include that colony; stoats were trapped at Jackson Head with no predator control at Gorge River. Unfortunately for our study, but certainly not for the penguins, stoat numbers were low at all sites in 2017.

Our results indicate that landscape level control by 1080 appears to benefit Fiordland penguins by preventing high numbers of rats and stoats in seasons immediately following mast events in nearby forests. However, much more rigorous testing of this conclusion is required. We suggest that this study be repeated in the season following the next major masting in the adjacent forests.

Interestingly, tawaki do not perceive stoats, possums, rats or mice as a threat. Possums, rats and mice do not appear to pose a threat to these penguins.

The full report is available below along with reports from The Tawaki Project, an explanation of the predator plague cycle that follows beech mast events and two further reports about this little understood species.

The Trust is hugely grateful to all those who have supported this project, including the Department of Conservation, Geoff Robson/Greenstone Helicopters, Taronga Conservation Society Australia (Taronga Zoo, Sydney) and Wellington Zoo Conservation Fund. A full list of acknowledgements completes the report (link below).