Interactions among behavioral responses of baleen whales to acoustic stimuli, oceanographic features, and prey availability
Abstract
The 2010-13 field efforts of SOCAL-BRS have been a resounding success, with a significant number of both tag deployments and controlled exposure experiments (CEEs) conducted. We have completed active prey mapping for baleen whales for most of the CEEs (2011-13 - see below). One of the initial findings was that blue whales that were surface feeding on krill showed less response to playback experiments while the feeding behavior of deep-feeding whales in the initial analysis responded when playbacks occurred (Goldbogen et al. 2013). The primary driving factor appears to be the specific mode of feeding behavior and prey availability in the water column, suggesting that blue whales in an abundance of krill may react categorically differently to acoustic stimuli than blue whales feeding on more dispersed prey. Analyses of the foraging behavior of large cetaceans have generally focused on either correlations to environmental conditions at a regional scale or observed surface behaviors conducted at a local scale. In contrast, we are measuring fine scale prey distribution, abundance, and behavior in combination with fine-scale measurements of individual whale foraging behavior within the context of CEEs. Our specific goals are to: (1) augment the current research paradigm to better understand how prey influence baleen whale foraging behavior; and (2) apply these direct measurements to explain variance in whale behavior as a function of both prey and exposure to simulated and realistic Navy MFA sonar. We propose to continue this ground-breaking contextual data collection paradigm using prey-mapping research concurrent with baleen whale tagging and MFA sonar CEEs for the final years of the SOCAL-BRS project. This will be conducted for blue whales, but with a particular focus on collecting a parallel data set for fin whales as well. Combining prey information, water column, and concurrent tag data will help us understand the ecology of blue and fin whales on fine scales. Specifically, we will measure how prey density throughout the water column influences whale foraging behavior and affects the probability of response to Navy MFA sonar. Without measurements of the prey field and oceanic conditions at the scale relevant to the tagged whale, it is impossible to separate behavioral response effects from experimental sounds versus those driven by nonanthropogenic environmental factors. We will apply spatial statistical models (e.g., generalized additive mixed models) with whale behavior as a response (e.g., feeding versus traveling, ascent rate) to examine environmental and prey effects on behavior with BRS playback condition (MFA sonar or silent control) as categorical covariates with an interaction term. These methods will help separate the experimental effects from background behavioral changes. We have conducted similar experimental work to determine the effects of oceanography and prey on other baleen whale species (e.g., (Friedlaender et al. 2009, Hazen et al. 2009, Goldbogen et al. 2013, Friedlaender et al. 2014) and have the expertise to successfully conduct similar work as part of the SOCAL experimental design. Notably, the SOCAL-BRS efforts in 2013-15 have and will continue to use operational Navy MFA sonar sources in CEEs in addition to the much smaller scaled sources used previously.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Aug 12, 2016
- Source ID
- N000141512647
Entities
People
- Elliott L. Hazen
Organizations
- Office of Naval Research
- United States Navy
- University of California, Santa Cruz