Weinrich et al . Behavior of Megaptera novaeangliae during biopsy 



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There have been other studies of the response of 

 humpback whales to human-induced stimuli. In Alaska, 

 17 humpback whales exhibiting "affected" behavior 

 associated with the proximity of vessels increased their 

 mean and maximum dive intervals, while their mean 

 blow interval decreased (Baker and Herman 1982). In 

 comparison, although the whales in our study did not 

 consistently increase the length of their dives follow- 

 ing the biopsy, blow intervals decreased slightly. In 

 both studies, whales decreased surface-interval/dive- 

 time ratios on average. The whales in our study and 

 in that of Baker and Herman (1982) also responded 

 with an increased rate of net movement. 



Our results generally agree with other studies of the 

 reactions of baleen whales to a variety of human- 

 induced stimuli. Richardson et al. (1985) found that 

 bowhead whales Balaena mysticetus respond to a vari- 

 ety of man-made stimuli (drillships, vessels, aircraft) 

 by reducing their surface-interval/dive-time ratios. 

 Swimming speeds increased in response to vessel traf- 

 fic. Migrating gray whales, by comparison, have been 

 reported to slow down as their migration route took 

 them toward simulated offshore industrial activity 

 (Malme et al. 1983, 1985). Bauer and Herman (1985) 

 found that humpback whales on Hawaiian breeding 

 grounds reduced their surface interval as vessels ap- 

 proached closely. The blow interval decreased as either 

 the proximity or the number of vessels increased. 

 Similarly, pod speed increased as vessels approached. 

 Hence, the net effect in all these studies was the same 

 as we have found; namely, that the animal avoids the 

 source of the stimulus. 



It is important to note that the reactions we describe 

 in most cases were elicited by a noxious stimulus of 

 brief duration and low-to-moderate amplitude. On this 

 basis, our findings likely underestimate the effects of 

 a more prolonged noxious stimulus, or one of greater 

 force. For example, extreme responses, including 

 escape, hard tail flicks, and immediate submergence, 

 has been documented in harpooned right whales Euba- 

 laena glacialis (Scammon 1874) and fin whales Balae- 

 noptera physalus (Lambertsen and Moore 1983). 



In the context of current management problems, the 

 response of a whale to a prolonged sublethal noxious 

 stimulus is a critical issue, as habitat intrusion may 

 establish conditions of continuing, if not constant, 

 exposure to diverse noxious stimuli. Recognizing this, 

 Bauer and Herman (1985) considered the relationship 

 of stimulus amplitude and duration (expressed as the 

 number of whale-watching vessels and the length of 

 time a whale group was in close proximity to whale- 

 watching vessels) to elicited responses in their study 

 of the effects of vessel traffic on humpback whales. 

 In both cases, their data indicate a graded response 

 in strenuous episodes of breaching, lobtailing, and 



flippering behavior and in movement away from the 

 path of vessels. 



Although our present study was not designed to 

 evaluate the effects of increasing stimulus duration, 

 including that approximated by stimulus repetition, the 

 special case of SI4 is illuminating. Its progressively 

 increasing reaction to repeated biopsy strikes was 

 dramatic. After the first strike, the whale seemed 

 unperturbed. After the second, it appeared, from its 

 trumpet blowing and stationary position, to be annoyed 

 but passive. After the third, it reacted with great in- 

 tensity and subsequently appeared exhausted. 



Based on these observations we conclude that 

 adverse responses to rapidly repeated or prolonged 

 noxious stimuli in whales may be incorrectly modeled 

 as a linear function. Given the lack of any detectable 

 response to the biopsy procedure in some animals, 

 there seems to be a threshold for stressor amplitude 

 below which no response will occur. Further, this 

 threshold of tolerance may be dependent upon the 

 specific activity in which the animal is engaged imme- 

 diately prior to the time the stressor is applied; e.g., 

 in our study animals engaged in feeding were unlikely 

 to react to the strike of a biopsy dart. There likely are 

 also individual differences in this threshold, as sug- 

 gested by the wide variation in reactions observed. 



Moreover, although one evidently can expect a 

 graded response in the disturbance of the animal above 

 its tolerance threshold, such gradation might be better 

 modeled as an exponentially increasing stimulus- 

 response function. As such, continuous or rapidly 

 repeated moderate-level noxious stimulation could 

 potentially lead to a general somatic alarm reaction, 

 with endocrinologic consequences (Selye 1936, 1946). 

 Thus, one of the important implications of this study 

 for current management strategies to promote the 

 recovery of endangered whale populations is that un- 

 controlled increases in the level or frequency of nox- 

 ious intrusion into cetacean habitat may, suddenly and 

 unexpectedly, have serious deleterious effects. 



Acknowledgments 



We are grateful to M. Gassel and P. Raid of the Ceta- 

 cean Research Unit, and S. Frohock of the Atlantic 

 Cetacean Research Center, who helped collect the data 

 presented in this study. S. Sears, T. Leland, C. Gun- 

 son, S. Larkin, Dr. R. Schaper, and Dr. D. Senior 

 provided great assistance at sea and in logistical 

 arrangements. D. Beach, T. McKenzie, and two anon- 

 ymous reviewers provided helpful comments on an 

 early draft of the manuscript. Funding for the study 

 was provided by the National Marine Fisheries Service 

 (PO 40EANF-501-0396) and Contract 50EANF-00094, 



