ROMBERG TIBURON CENTER OBSERVATION OF BLUE WHALE CALLS FROM PIONEER SEAMOUNT Michael D. Hoffman, 1 Newell Garfield, 2 and Roger Bland 1 1.Physics and Astronomy Department and Romberg Tiburon Center for Environmental Studies, San Francisco State University 2. Department of Geosciences and Romberg Tiburon Center for Environmental Studies, San Francisco State University

We have carried out a high-statistics study of the “B” call of the blue whale (Balaenoptera musculus), as observed from the Pioneer Seamount underwater observatory, 90 km off the California coast. Data were collected in several contiguous blocks, via an underwater cable, over a period of 13 months. The continuous operation and the non-invasive nature of the observations make this a homogeneous and unbiased sample. We find a remarkable degree of consistency in the “B” calling patterns of the blue whale: The calling interval is constant to 4% accuracy; and the frequency of calls is adjusted to be the same, over long periods of time, and for all calling individuals, to an accuracy of 0.5 %. The calling frequency itself is apparently changing with time, with all individuals visiting Pioneer Seamount tracking the change. Two substantially different types of calling sequences are observed, each at the same frequency, each with its well-regulated (but different) calling interval. A number of questions concerning blue-whale acoustic activity are raised. What types of behavior correspond to these two calling sequences? What is the function of the precisely regulated call frequency? How do individuals of different size adjust their call to the same frequency? And what sense is able to perceive frequency to this remarkable accuracy? And finally, is there any information transmitted by acoustic calling which is so remarkably invariant? ABSTRACT