Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September 2008.In this thesis, I provide quantitative descriptions of toothed whale
echolocation and foraging behavior, including assessment of the effects of noise
on foraging behavior and the potential influence of ocean acoustic propagation
conditions on biosonar detection ranges and whale noise exposure. In addition
to presenting some novel basic science findings, the case studies presented in
this thesis have implications for future work and for management.
In Chapter 2, I describe the application of a modified version of the Dtag to
studies of harbor porpoise echolocation behavior. The study results indicate how
porpoises vary the rate and level of their echolocation clicks during prey capture
events; detail the differences in echolocation behavior between different animals
and in response to differences in prey fish; and show that, unlike bats, porpoises
continue their echolocation buzz after the moment of prey capture.
Chapters 3-4 provide case studies that emphasize the importance of
applying realistic models of ocean acoustic propagation in marine mammal
studies. These chapters illustrate that, although using geometric spreading
approximations to predict communication/target detection ranges or noise
exposure levels is appropriate in some cases, it can result in large errors in other
cases, particularly in situations where refraction in the water column or multi-path
acoustic propagation are significant.
Finally, in Chapter 5, I describe two methods for statistical analysis of
whale behavior data, the rotation test and a semi-Markov chain model. I apply
those methods to test for changes in sperm whale foraging behavior in response
to airgun noise exposure. Test results indicate that, despite the low-level
exposures experienced by the whales in the study, some (but not all) of them
reduced their buzz production rates and altered other foraging behavior
parameters in response to the airgun exposure.Work presented in this thesis was supported by a National Science Foundation
Graduate Research Fellowship, the WHOI Ocean Life Institute (Grant Numbers
32031300 and 25051351), the Office of Naval Research, the U.S. Department of
the Interior Minerals Management Service (Cooperative Agreement Numbers
1435-01-02-CA-85186 and NA87RJ0445; WHOI Grant Number 15205601), the
Industry Research Funding Coalition, and the WHOI/MIT Joint Program in
Oceanography/Applied Ocean Science & Engineering (including a Fye Teaching
Fellowship)
