Acoustic Analysis of Body Condition in the Northern Right Whale

摘要

Northern right whales are known to be undergoing chronic reproductive failure, when compared to Southern right whales. Possible contributing stressors include inbreeding, chemical exposure, infectious disease, man-made noise and inadequate nutrition. We have so far developed evidence of possible increased chemical exposure in feeding northern right whales. The ONR-funded portion of our program focuses on body-fat condition as an index of health. The current ONR funded portion of this long term program tests if body condition as measured by blubber thickness is predictive of reproductive success. To do this, available acoustic technology had to be adapted and improved to measure blubber thickness in live free-ranging right whales. We have developed, and continue to refine the use of analog-mode ultrasound to measure blubber thickness while a right whale surfaces for air. The acoustic blubber-depth echoes so obtained are normalized for sampling position upon the animal, and for animal size. These data are then compared with known catalogued reproductive history for each animal so measured. This is the first time that body condition has been measured in any live cetacean unrestrained. Our preliminary data suggest that measures of body condition will be useful in predicting the next calving interval, thus giving a predictive tool for monitoring right whale populations. The mechanical pole system we have developed is proving to be useful for the rapid deployment of suction cup tag systems on to the backs of large whales with minimal disturbance to the animal. In the Bay of Fundy we will deploy tags on right whales for the WHOI Tyack laboratory in July and August of this year whilst measuring blubber thickness concurrently. Our hardware and software configuration may also have utility to other projects that require high data rate acquisition of acoustic echoes of any solid or liquid - animal, water or sediment.