Baleen whale responses to a high frequency active pinger: Implications for upper frequency hearing limits

Abstract

In order to test the possibility of using high frequency pinger tags to track baleen whales on Navy instrumented ranges, three blue (Balaenoptera musculus) and one humpback (Megaptera novaeangliaea) whales were exposed to two high frequency pingers. The pinger frequencies were 37 and 45 kHz, with estimated received levels between 106 and 134 dB re 1 μPa. The whales were monitored prior to the exposure in order to establish their behavioral state and to acclimate them to the presence of the boat. Two of the blue whales were deep feeding, while the third blue whale and the humpback whale were traveling with intermittent bouts of possible foraging near the surface. Each exposure lasted approximately 30—40 minutes, and the whales were observed for an additional two to three surfacing intervals post-exposure. None of the blue whales demonstrated any behavioral response. The humpback whale’s response was inconclusive, as other foraging animals entered the area at the same time; however, it is likely there was no response. These data may begin to provide information on the upper frequency limits of baleen whale hearing, as these species have responded to Navy sonar-like sounds at lower frequencies but similar received levels and behavioral states.