A whale alarm fails to deter migrating humpback whales: an empirical test

Acoustic deterrents were tested for their ability to deter humpback whales (Megaptera novaeangliae) from potential sources of entanglement. Low frequency (3 kHz, 135 +/- 5 db, 5 s emission interval and 400 ms emission duration) alarms were tested. Alarms were placed in the center of the northerly migration path (southern hemisphere) of humpback whales. Observers, who were unaware of the alarm status (i.e. on/off) tracked the pods as they passed the alarms. Sixty percent of the pods (N=137) passed within the assumed detectable range (500 m) of the alarm. Sixty five percent passed the alarm while it was onand 52% when it was off. Therefore, there does not appear to be any noticeable response from the whales to the alarms. There were no differences in the directionality, course heading or dive duration within the detectable range of the alarm, whether on or off. It is therefore unlikely that single alarms currently used with trap or pot lines are effective at reducing interactions with humpback whales.