Body condition as a predictor of behavioral responses of cetaceans to sonar
Abstract
Behavioral Response Studies (BRS) have successfully quantified cetacean responses to navy sonar, but they have also revealed significant variability in individual behavior and response thresholds. Some of this variability has been attributed to environmental or behavioral contexts, but a significant portion remains unexplained. The energetic condition of an individual (hereafter, body conditi"on"") is one such potentially important context variable, and is also a key indicator of individual fitness. A significant body of em"pirical and theoretical work indicates that more energetically stressed animals with lower body condition tend to take greater risks to obtain greater foraging rewards. With increasing availability of BRS data and recent developments in tag data analysis, there is now an opportunity to test whether body condition also predicts behavioral responsiveness of cetaceans to navy sonar. Quantifying the effect size of such relationship can directly address data needs for population consequences of disturbance (PCoD) models that incorporate body conditoin as the key state variable. We propose to analyze existing data from three cetacean species (sperm whales, humpback whales, and blue whales) from two BRS studies (3S and SOCAL-BRS) to quantify the explanatory power of individual body condit"ion as a predictor of behavioral responses. To infer body condition from animal-borne data loggers (here, DTAGs) we will use the ""gl""ide method"" to estimate tissue density, a proxy for total lipid store carried by an individual. The estimated body density will then" be used as an explanatory variable for behavior responses, with a focus on cessation of foraging. Our main hypothesis is that individuals in poorer body condition wil be less likely to give up foraging opportunities and may therefore be less behaviorally responsive to sonar. We can test this hypothesis in an efficient way by building upon existing data products (e.g. lunge detections) and established statistical methods (e.g. state-based models) for each species. Also body density estimates for humpback whales and blue whales will be available through collaborators using the glide method. The project can therefore be completed in two main analysis steps, with two key outcomes: 1) glide method analysis to estimate tissue density for sperm whales, quantifying baseline variability in body condition for this speces; and 2) behavior response analysis with body condition as an explanatory covariate, quantifying the effect size for the potential relationship(s) within and across the three cetacean species.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Aug 15, 2019
- Source ID
- N000141912479
Entities
People
- Saana Isojunno
Organizations
- Office of Naval Research
- United States Navy
- University of St Andrews