Triple Observer Survey Method for Feral Animals

Client: NSW Department of Primary Industries and Regional Development

Helicopter surveys of feral pigs, goats, and kangaroos aimed to measure population size to evaluate control operations. Three observers were used to improve detection, but no existing statistical method could properly analyse data from three observers at once.

We developed a new modelling approach to handle triple observer survey data, accounting for the possibility that observers might influence each other's sightings.

Outcome: The new method produced more reliable population estimates and revealed that observers did influence each other's detections. This enabled wider use of triple observer surveys for estimating animal abundance from aerial surveys.

Method: A novel triple observer extension of mark-recapture distance sampling (MRDS).