Comparing the foraging efficiency of beaked whales on and off naval ranges
Abstract
The US Navy has invested heavily in studying anthropogenic noise and its potential effect on marine mammals. Behavioral response studies (e.g. BRS, SOCAL and 3S) and resultant modeling studies (e.g. LATTE, MOCHA, PCAD and PCoD) are utilized to monitor disturbance of individuals to sonar in order to assess the influence of naval operations on marine mammal populations. When marine mammals are disturbed, they may remain in the same location but alter their behavior, or move away from the disturbance. ONR has funded efforts to create a ‘Population Consequences of Acoustic Disturbance’ (PCAD) model, which addresses how anthropogenic noise may affect marine mammals and how behavioral and physiological response data could inform our understanding of population level effects (New et al. 2013). The framework of the PCAD model has subsequently been expanded to include all disturbances, entitled ‘Population Consequences of Disturbance’ (PCoD) (New et al. 2014). These modeling approaches, designed to understand how disturbance might affect whale populations, require knowledge of direct acute or indirect chronic effects on individuals. Detailed knowledge of an individual’s metabolic and caloric intake costs associated with disturbance would significantly benefit population level assessments. Collecting such data to help determine the vital rates of free-swimming odontocetes is not currently possible. However, behavioral parameters (e.g. fluking rates and prey capture attempts) associated with movement and foraging have been collected using DTAGs and can act as proxies for changes in energetic intake and expenditure (Miller et al. 2009). By quantifying aspects of locomotion and foraging, levels of energetic expenditure and foraging efficiency can be assessed. The ability to measure these parameters is relevant because, where disturbance leads to flight, whales may incur locomotion costs as they move to habitats of potentially differing quality. In these habitats, prey may vary in type or abundance, leading to changes in foraging behavior and efficiency. To understand whether the energetic expenditure and foraging efficiency of whales inhabiting naval ranges is affected by disturbance, it is important to a) understand whether foraging behavior varies within a region, and b) investigate how comparable sub-populations behave and forage in the absence of regular sonar exposure. The Great Bahama Canyon is an ideal location for such a study. DTAGs will be deployed on a subpopulation of Blainville’s beaked whales (Mesoplodon densirostris) at the Atlantic Undersea Test and Evaluation Center (AUTEC), and in areas adjacent to it, where sonar has displaced members of this sub-population (Tyack et al. 2011). Whales from a separate sub-population off southwest Abaco Island (SA) will also be tagged. SA lies only 170 km north of AUTEC, yet is an area where whales are not regularly exposed to sonar. Longitudinal beaked whale population studies have taken place at both study sites (AUTEC, since 2005 and SA, since 1997). The detailed nature of studies on exposed and unexposed sub-populations, combined with the small geographic distance between them, presents a data rich and unique situation to investigate foraging differences. By comparing in detail the foraging choices made at 1) AUTEC, 2) SA and 3) displacement habitats, this study will, for the first time, provide a means to examine variation in foraging efficiency and energetic costs resulting from sonar disturbance.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Aug 12, 2016
- Source ID
- N000141512553
Entities
People
- Lloyd Tyack
Organizations
- Office of Naval Research
- United States Navy
- University of St Andrews