Killer whales respond to anthropogenic activities in various ways, including changes in acoustic behavior, surface behavior, dive behavior, travel direction, and behavioral activity states.
For example, one study demonstrated that Southern Resident killer whales increase their calls' amplitude in response to vessel noise (Holt et al. 2009). Another study showed that Southern Residents perform surface-active behaviors (e.g., breaches, tail slaps) after close vessel approaches (Noren et al. 2009). Our past work on bottlenose dolphins, a close relative of Southern Residents, shows these responses have relatively small but measurable energetic consequences that vary by behavior, intensity, and repetition rate (Noren et al. 2012, Noren et al. 2013, Holt et al. 2015, Noren et al. 2017a).
In our most recent project on Southern Residents, we quantified the cumulative energetic costs of a suite of responses to disturbance from vessels and noise in terms of increased energy expenditure relative to the daily activity budget (Noren et al. 2017b).
The results demonstrate that the cumulative change in energy expenditure related to short-lived behavioral and acoustic responses, swim speed changes, and changes in activity states are negligible to very low. However, reduced foraging behavior is a ubiquitous response to various anthropogenic disturbance sources in odontocetes, including Southern Resident killer whales.
Contact
Dawn Noren, Research Fishery Biologist, Marine Mammal Ecology Team
