First indications that northern bottlenose whales are sensitive to behavioural disturbance from anthropogenic noise

Abstract

Although northern bottlenose whales were the most heavily hunted beaked whale, we have little information about this species in its remote habitat of the North Atlantic Ocean. Underwater anthropogenic noise and disruption of their natural habitat may be major threats, given the sensitivity of other beaked whales to such noise disturbance. We attached dataloggers to 13 northern bottlenose whales and compared their natural sounds and movements to those of one individual exposed to escalating levels of 1–2 kHz upsweep naval sonar signals. At a received sound pressure level (SPL) of 98 dB re 1 μPa, the whale turned to approach the sound source, but at a received SPL of 107 dB re 1 μPa, the whale began moving in an unusually straight course and then made a near 180° turn away from the source, and performed the longest and deepest dive (94 min, 2339 m) recorded for this species. Animal movement parameters differed significantly from baseline for more than 7 h until the tag fell off 33–36 km away. No clicks were emitted during the response period, indicating cessation of normal echolocation-based foraging. A sharp decline in both acoustic and visual detections of conspecifics after exposure suggests other whales in the area responded similarly. Though more data are needed, our results indicate high sensitivity of this species to acoustic disturbance, with consequent risk from marine industrialization and naval activity.

Experimental field studies to measure behavioral responses of cetaceans to sonar

“…Stimpert et al (2014) observed similar patterns of be havioral response in a Baird's beaked whale to simulated 3− 4 kHz sonar CEEs, although response intensity abated more quickly following exposure in that individual compared to the Ziphius response measured by De Ruiter et al (2013a). These combined results are consistent with the findings of Tyack et al (2011) andMiller et al (2015) in demonstrating clear, strong, and pronounced behavioral changes, including sustained avoidance with associated energetic swimming and cessation of feeding behavior at quite low received levels (~100 to 135 dB re 1 µPa) for exposures with relatively nearby (2 to 5 km) sound sources in simulated sonar CEEs.…”

“…Cox et al 2006). The strong response for a bottlenose whale measured by Miller et al (2015) was particularly striking in that it resulted from a 1−2 kHz sonar signal, which is even further from the species-typical sound production than the 2−7 kHz sonars in the other studies, presented over 5 km from the source in an area where operational military sonars seldom occur. While the CEE results for beaked whales now span 4 different species in different parts of the world, these studies have all involved small sample sizes (1 to 2 individuals per species), and additional experimental work is clearly needed.…”

“…These include studies of behavioral state-switching in blue whales using hidden Markov models (DeRuiter et al in press), as well as individual response analyses using structured expert severity scoring and quantitative change point statistical methods. Beaked whale CEEs from SOCAL-BRS expanded our understanding of the nature of behavioral response in this group of particularly sensitive species, adding to the findings of Tyack et al (2011) andMiller et al (2015) described in the previous sections. DeRuiter et al (2013a) documented pronounced and sustained behavioral changes in 2 Cuvier's beaked whales, marking the first ever CEEs for this high priority species.…”

Impacts of Navy Sonar on Whales and Dolphins: Now beyond a Smoking Gun?

“…In fact, significant impacts to beaked whales could occur at levels lower, and from sound sources at greater distances from animals, than previously thought, arguably making current US mitigation guidelines for mid-frequency active sonar ineffective at preventing wide-scale impacts to whales. Miller et al (2015) determined that Northern bottlenose whales (Hyperoodon ampullatus) showed a "high sensitivity . .…”

Coupled Modeling of Hydrodynamics and Sound in Coastal Ocean for Renewable Ocean Energy Development

“…Ray tracing was used to study the impact of the noise from the seismic air guns on fish behavior (Hovem et al, 2012) and to estimate the received sonar signals by the northern bottlenose whales (Miller et al, 2015). Parabolic equation (PE) was also utilized to estimate the sound exposure level to seals around the pile driving location near a wind farm construction site (Hastie et al, 2015).…”