Since early 2018, ZIP (with the support of DOC and Predator Free 2050 Limited) has been carrying out a trial at a field site in the Perth River valley, South Westland, which aims to completely remove possums, rats, and potentially stoats from 12,000 hectares of rugged back-country, and to then permanently prevent these predators from re-establishing. In autumn/winter 2019, ZIP carried out an initial predator removal operation using a modified technique for applying aerial 1080. This operation was carried out in two phases, each consisting of two applications of non-toxic prefeed, followed by a single application of toxic bait.
The Perth River field site contains Himalayan tahr, which are highly valued by hunters. While there is little evidence to suggest that ‘standard’ aerial 1080 operations have an impact on tahr populations, ZIP recognised that some aspects of the modified technique used in the predator removal could elevate the risk to tahr. In order to better understand this risk, ZIP invited the Game Animal Council (GAC) to collaborate on a research programme to assess tahr survivorship through the Perth River predator removal operation.
Before the predator removal operation, a sample of 21 tahr were fitted with collars containing radio transmitters. The sample was made up of nannies and juveniles of both sexes, as these were deemed to be more likely to be at risk of 1080 poisoning than adult males.
These tahr were monitored throughout the operation using Sky Ranger, an automated system designed to monitor wildlife from an aircraft. Sky Ranger flights were carried out as soon as practically possible before and after each application of prefeed or toxic bait, to provide information about each individual tahr’s potential exposure to 1080.
Three tahr are fitted with collars containing radio transmitters. During this procedure, the tahr wear blindfolds and horn protectors to ensure their safety and welfare.
The high mobility of tahr, along with the unavoidable time lapses between 1080 applications and Sky Ranger monitoring, meant that we could not confirm with certainty the exposure of some individual tahr to 1080 baits. However, statistical analysis based on the locations of radio-collared tahr during each Sky Ranger flight indicates that 11-15 of the radio-collared sample were exposed to 1080 during the first phase of the operation, and 8-14 were exposed during the second phase. All of these tahr survived the operation.
The full report, authored by Geoff Kerr, Professor of Environmental Management at Lincoln University and former Game Animal Councillor, is available here.
The results of this trial suggest that tahr survival during the Perth River valley predator removal operation was extremely high, and there was no evidence that any tahr died as a result of the operation. Together, these results support the general view that tahr populations are unlikely to be at risk during aerial 1080 operations.
ZIP appreciated the opportunity to work closely with the Game Animal Council on this project, which also benefitted from the advice and feedback of the Department of Conservation, the New Zealand chapter of Safari Club International, the New Zealand Deerstalkers’ Association, and the New Zealand Professional Hunting Guides Association.
“The Game Animal Council was pleased to contribute to this project. It is critical that pest control operations and the use of toxins are based on good science, which is why our collective work on the Perth Valley operation that showed aerial 1080 to have little to no impact on tahr is so important. We are excited about the animal management and conservation opportunities that will result from this ZIP-led work.”