Behavioral responses of summering humpback whales to vessel traffic : experimental and opportunistic observations

Baker, C; Herman, L

Results of research on the responses of whales to vessles. Looked at respiratory behavior, whale movement, changes in aerial, feeding, and social behavior. Observed whales in Frederick Sound and Bartlett Cover, Glacier Bay National Park. Some conclusions: 1. Vessels cause social disruption, (maybe): "The increased levels of aerial behavior and changes in pod composition [this is in reference to GLBA only] could both be interpreted as indications of social disruption" p.34. 2. Best of a bad job: "Although the simple residency of the focal pod in Bartlett Cove indicates a considerable tolerance for vessel traffic, the possibility cannot be excluded that these animals were simply "making the best of a bad situation". Hydroacoustic surveys of Bartlett Cove during the summer of 1982 indicated the residency of a large school of capelin (Wing and Krieger 1983). For the whales, the availability of this rich food source may have outweighed the disadvantages posed by the high level of vessel traffic in the cove. It is also probable that Park Service regulations controlling the speed and approach of vessels helped to mitigate the disturabcne of whales in the cove."p. 34. Also includes dramatic case histories of responses to vessels. "The displacement of whales from a preferred feeding site or the interruption of feeding, including nursing of calves, during this short feeding season may be the most serious relult of human disturbance. Since humpback whales fast on the winter breeding grounds, they have only a few months each summer and fall in which to gather enoiugh food for a year. Although these animals must be able to tolerate occasional or intermittent interruption of their feeding, chronic disturbance will undoubtedly have a cumulative and deleterious effect on their fitness." Cumulative effects of repeated vessel encounters = potentiation: pg. 40: "A factor common to all three of the case histories was the repeated passby of vessels during a relatively brief period of time. As indicated by the previous analysis of vessel density in Bartlett Cove, vessel traffic can have a cumulative or additive effect on the behavior of whales." Habituation to noise vs. the potentiation: Studies of gray whales, Eschrictius robustus, and bowhead whales indicate that these animals may tolerate or habituate to fixed or slow-moving sources of continuous acoustic stimuli, such as drilling platforms or playback of industrial noise (Malme et al. 1983; Richardson et al. 1985). Erratic or rapidly moving stimuli, however, seem to have the opposite effect on humpback whales, resulting in a potentiation to respond. "Ultimately, it would be valuable to estimate the direct energetic "cost" of human disturbance to humpback whales. ..... In other words, how much energy is expended or lost, as a result of disturbance, that might otherwise be divoted to reproduction? " Whales interpret acoustic stimuli before responding, in ways that we don't fully understand: "A whale's interpretation and subsequent response may be influenced by the perceived size of the vessel, its speed, its direction, the predictability of its course, and the individual whale's past experience, as well as by the simple intensity of a vessel's noise signature."

Behavioral responses of summering humpback whales to vessel traffic : experimental and opportunistic observations

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