On-board calculation and telemetry of the body condition of individual marine mammals
Abstract
Many studies have demonstrated that human activities, including naval sonar can affect biologically-important behaviors of marine ma""mmals (Southall et al., 2016), but the extent to which such effects might lead to biologically relevant changes in individual health"", vital rates, and population health is largely unknown (National Research Council, 2005, 2016). Modelling efforts have stressed the" role of body condition of individual animals as an important indicator of individual health that is likely to affect survival and r"eproduction of marine mammals (New et al., 2014). A recent NRC report on how to address cumulative effects of disturbance stressed t""he potential benefit of a method that would enable evaluation of changes in individual health (NRC, 2016). Measures of individual he"alth are particularly challenging with free-ranging cetaceans that do no haul-out on land for assessment. Approaches such as visual" or photogrammetric assessment of body condition are effective in some circumstances, but require re-sighting of animals to measure" longitudinal changes in individual animals. These issues highlight a current need to develop tag-based tools to measure changes in health (body condition) longitudinally in tagged individuals. Such a tool would have the potential to directly show the consequence"s of disturbance in terms of the ability of animals to obtain sufficient resources to survive and reproduce, within the context of n""atural variability in free-ranging marine mammal populations. In direct response to this need, we"" propose to develop, deploy and iterate a novel tag system that will be capable of using ARGOS telemetry over a time scale of months" to send a body condition metrick of individual tagged-animals. Body condition is defined in this work as total body lipid store whi"ch can be estimated using the ""glide"" method (Miller et al., 2016) to estimate body-density ( a function of lipid store). To date, l"ong-term measurements of body condition via body density of marine mammals has only been possible with elephant seals that conduct d"rift dives resting motionless at depth. Few other species conduct drift dives, and drift dives are often uncommon even for species t""hat do conduct drift dives. The ""glide"" method enables estimation of body density of any animal that conducts glides during descent"" or ascent phase of dives, which is ubiquitous behavior and should therefore be applicable to all marine mammals. To date, the metho""d has been successful using archival tag data with several species of cetaceans, including both toothed and baleen whales as well as" seals. Our goal is development of a system that can effectively relay lipid-store body condition for any marine mammal with minimal" bandwidth. In the first step toward that longer-term goal, here we propose to develop the first working system with elephant seals,"" which enables maximum possible validation of the method, against drift dive and shore-based body condition measurements. This will"" represent a major advance in the transition to on-board calculation and telemetry of body condition, but with relatively low-risk e""ffort as body density using the glide method has already been achieved with elephant seals, and the hardware challenges for seal tag""s are less than for cetacean tags. Techniques and characteristics of the resulting system will be shared with the community, enablin""g wider adaptation of this methodology to measure body condition of marine mammals, with a particular view to enable remote measurem"ent and telemetry of the body condition of cetaceans.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Sep 01, 2017
- Source ID
- N000141712757
Entities
People
- Patrick Miller
Organizations
- Office of Naval Research
- United States Navy
- University of St Andrews