Dr. John Hildebrand
Ph.D. Applied Physics, Stanford University, 1983.
I am interested in how sound is used by marine mammals and how sound can be used as a tool for assessment of marine mammal populations. Recent advancements in acoustic recording technology have allowed long-term and broad-band records of underwater sound to be collected. These recordings open new windows into the behavior and distribution of marine mammals (as well as other marine organisms such as fish). Over the past decade, I have been studying how sound can be used to better understand mysticete whales, such as blue and fin whales. Some of the key results of this work are that sound may be an effective means for determining the population structure of these animals, since the songs produced by blue and fin whale have regional dialects, and these may be used by the animals as an aid for mate selection. Likewise, we have discovered that different characteristic sounds are associated with foraging and with mating behavior, and that these sounds are used with different intensity over a seasonal cycle. With the availability of expanded recording bandwidth, we have recently begun to make long-term recordings of odontocetes (toothed whales and dolphins). I has been possible to use echolocation click structure for species identification, and also to identify population structure using differences in echolocation clicks. A future challenge will be to use passive acoustic data for quantitative estimates of marine mammal abundance.