How many detections do we need?
We know the further a wallaby is from our flight path or ground searching route the less likely it will be detected. This has implications for determining whether wallabies have been eradicated, or whether some animals remain that have not been detected during surveillance. How quickly the detection probability declines with distance from our search route is unknown and estimating this relationship is the main objective of this research. Detection probability can be estimated in field trials by recording (1) whether a gps-tracked animal is detected or not, and (2) its distance from the searching route. Before we start the field trials it is prudent to know how many detections we might need to precisely estimate the detection probability.
Rachelle Binny (a Mathematical Biologist) has run computer simulations of the field trials to answer this question. This involves setting up a hypothetical scenario where we already know the “true” probability of detecting a wallaby over a range of distances. We then simulate the search and use this hypothetical “true” detection probability to generate artificial field data (whether an animal was detected during the search or not, and at what distance from the search path). Finally, we work backwards, using only the artificial field data to try and recover our known “true” detection probability. The more data we have, the more precise our estimate will be - our simulations suggest that 40 animals need to be detected (over a range of different distances) to obtain a reliable estimate of detection probability.
