When exposed AC220 to repeated levels of disturbance throughout the day, the net effect is an altered activity budget, in which killer whales spend less time feeding in the presence of boats than during no-boat, control conditions
(Lusseau et al., 2009 and Williams et al., 2006). A number of studies have demonstrated effects of noise from large ships on a variety of cetacean species, including Cuvier’s beaked whale (Aguilar Soto et al., 2006), North Atlantic right whale (Nowacek et al., 2004 and Rolland et al., 2012), beluga (Erbe and Farmer, 1998 and Erbe and Farmer, 2000) and fin whales (Castellote et al., 2012). These studies provide a hint that ship noise can reduce a whale’s foraging efficiency (Aguilar Soto et al., 2006); elevate the risk of ship strikes (Nowacek et al., 2004); and cause physiological stress that is detectable in hormone levels (Rolland et al., 2012). A combination of captive experiments and computer models (Erbe and Farmer, 2000) enabled researchers to estimate that icebreaker noise is audible to belugas and capable of eliciting behavioral responses and causing http://www.selleckchem.com/products/PTC124.html communication masking at ranges to 62 km. A temporary hearing shift was modeled to occur if a beluga stayed within 1–4 km of the icebreaker
for at least 20 min. Whales have evolved in an ocean environment that becomes naturally noisy during storms and surf zones, and they have evolved some mechanisms to compensate for noise. Fin whales change their song characteristics to try to maintain communication in high levels
of shipping noise (Castellote et al., 2012). There is some evidence to suggest that killer whales can compensate for increases in ambient noise by lengthening their calls (Foote et al., 2004) or increasing the source level of social calls (Holt et al., 2008). There is no evidence that killer whales can adjust their echolocation patterns to compensate for masked signals used in foraging, and no information on the upper limit to Selleckchem Fludarabine the whales’ compensatory mechanisms. In many behavioral response studies, the received levels that trigger responses are rarely known (but see (Williams et al., 2002a)). A recurring theme in the literature describing marine mammals and noise is that the most rigorous behavioral studies rarely report information on the acoustic stimulus, and the best acoustic studies often have very small sample size for inferring behavioral responses (Nowacek et al., 2007). No studies have yet examined the responses of killer whales to presence and activities of large ships. Such studies are needed (Wright, 2008). Global shipping represents a large and growing contributor to ocean ambient soundscapes (Hildebrand, 2009), and creative solutions are needed to quantify and mitigate impacts of chronic ocean noise on sensitive marine mammals (Wright et al., 2011).