Beaked whales and El Nino Will changes in beaked whale space use in response to large scale climatic events influence abundance estimation and responses to anthropogenic activities?
Abstract
Large-scale climatic events such as the El Niño-Southern Oscillation (ENSO) cycle have many documented effects on marine organisms,including cetaceans. Understanding how populations respond to such conditions is critical for predicting potential responses to climate change, and in understanding how responses to oceanographic conditions may intersect with efforts to estimate abundance or study reactions to anthropogenic activities. This is especially important for species that are known to be particularly vulnerable to anthropogenic activities. Beaked whales are a notable example of this, as they are particularly sensitive to anthropogenic noise (e.g., high-intensity mid-frequency active sonar), making them a priority species for management. It is therefore imperative that information on their space use and associated environmental drivers are obtained in order to adequately discern variation in behavior resulting from natural causes (e.g., changes to habitat) from anthropogenic stressors (e.g., sonar). Here, we propose to conduct an assessment of space use in relation to ENSO phases (El Niño, La Niña, neutral) for two beaked whale species that are resident to the waters off Hawai#i Island: Blainville#s beaked whale (Mesoplodon densirostris) and Cuvier#s beaked whale (Ziphius cavirostris). Preliminary analyses of existing sightings and satellite tag data for these populations indicate that their space use does differ by ENSO phase, and, potentially, the flavor of El Niño event (Central or Eastern Pacific). However, the existing sample size is limited duringEl Niño and neutral phases, especially for satellite tag deployments which provide more extensive information on space use and the movement decisions of individuals. Our proposed work will build upon these existing datasets, particularly the satellite tag dataset, and take advantage of the current El Niño phase and subsequent phases (neutral or La Niña) to obtain more comprehensive data across all ENSO phases. Further, in addition to some Argos location-only (SPOT6) satellite tags, we will use SPLASH10-F tags to obtain higher quality (resolution and accuracy) location data and dive behavior log data (summarized dive and surface records) to better infer functional relationships and overall movement behavior. Satellite tag data will be geo-processed with static and dynamic habitat variables to assess habitat use among the different phases. Ranging behavior (e.g., range-use ratios, home range size, net-squared displacement) will be characterized to evaluate the influence of ENSO on the spatial distribution of tagged whales. We will also collect biopsy samples to gain insight into the foraging ecology (e.g., trophic level, diet preferences) through stable isotope analysis;obtaining more samples for this analysis will serve useful for comparison with existing biopsy samples that have been analyzed for stable isotopes (e.g., whether there are changes in proportion of prey types consumed during different ENSO phases). Field efforts for tag deployment and biopsy sample collection will be undertaken across three years, leveraging field work in the same area funded to work with other species.Collectively, our proposed work will generate information on the environmental factors influencing the space use of two beaked whale species in Hawai#i, which will be vital for projecting risk and response to anthropogenic activities as well as for inference on population dynamics (e.g., biases in abundance estimation due to variable detection).--The Grantee s proposed work has been revised to only encompass the work to be funded by ONR.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Nov 08, 2024
- Source ID
- N000142412578
Entities
People
- Robin W Baird
Organizations
- Cascadia Research
- Office of Naval Research
- United States Navy