Relationship between visual counts and call detection rates of gray whales (Eschrichtius robustus) in Laguna San Ignacio, Mexico.
نویسندگان
چکیده
Daily acoustic calling rates of Eastern North Pacific (ENP) gray whales were measured on 6 days during 1 mo of their 2008 breeding season in the sheltered coastal lagoon of Laguna San Ignacio in Baja California, Mexico. Visual counts of whales determined that the numbers of single animals in the lower lagoon more than tripled over the observation period. All call types showed production peaks in the early morning and evening with minimum rates generally detected in the early afternoon. For four of the five observation days, the daily number of "S1"-type calls increased roughly as the square of the number of the animals in the lower lagoon during both daytime and nighttime. This relationship persisted when raw call counts were adjusted for variations in background noise level, using a simple propagation law derived from empirical measurements. The one observation day that did not fit the square-law relationship occurred during a week when the group size in the lagoon increased rapidly. These results suggest that passive acoustic monitoring does not measure gray whale group size directly but monitors the number of connections in the social network, which rises as roughly M(2)/2 for a group size M.
منابع مشابه
Changes in the acoustic behavior of gray whales Eschrichtius robustus in response to noise
Gray whales Eschrichtius robustus, while engaged in underwater signaling, circumvented noise in their environment by altering the structure and timing of their calls. Acoustic responses of whales to both naturally occurring and artificially increased levels of noise were documented during sound playback experimentation in San Ignacio Lagoon, Baja California Sur, Mexico. Nine acoustic parameters...
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ورودعنوان ژورنال:
- The Journal of the Acoustical Society of America
دوره 131 4 شماره
صفحات -
تاریخ انتشار 2012