Evaluation of a rat ultrasonic vocalisation as a novel audio-lure in two New Zealand forest settings

Actively attracting rats to trapping and baiting areas would potentially reduce the costs and labour required for controlling rats over large areas of forest. In this pilot study we explored the potential of using an ultrasonic lure to attract rats in two forest study areas: Tuateawa and Te Hoe. Data was collected from the Tuateawa study area over 21 discrete 24 h periods using tracking tunnels and cameras. Results indicated that rats were present more often at sites where a 50 kHz Norway rat ultrasonic vocalisation (USV) was played compared to sites where it was not played, although significance could not be attributed based on the low numbers detected. Interestingly, mice were detected at the Tuateawa study area more often at sites where the USV was played compared to sites where it was not played, with differences approaching a significant level of confidence (p = 0.059). At the Te Hoe study area, data was collected over a three-month period using A24 self-resetting traps and cameras. Results indicated that the weekly numbers of rats killed was higher (p = 0.025) at sites where USVs were played than at sites where USVs were not played. These findings indicate that rat USVs can attract rats and mice to trapping areas in New Zealand forest settings and support the view that including USVs in trapping methods could potentially enhance the efficiency of trapping and hence reduce the costs associated with current methods.