Quantifying key vital rates in Blainvilles beaked whale reproduction, including age at weaning, pregnancy rates and calf survival to inform Population Consequences of Disturbance models
Abstract
Understanding the population consequences of disturbance from operational activities is critical for the U.S. Navy to comply with take limits for protected marine mammals and to design effective mitigation and monitoring plans. This is particularly relevant for beaked whales, which are known to be sensitive to Navy sonar and because some beaked whale species exhibit long-term site fidelity to Navy ranges. To address this concern, the U.S. Navy has supported the development of the Population Consequences of Disturbance (PCoD) conceptual framework that traces the effects of disturbance through life functions to population status around which prediction models can be constructed. Despite the potential utility of PCoD models, key information on vital rates are lacking for beaked whales, which leads to a high degree of uncertainty in model predictions. Given these uncertainties, there is a need to fill these data gaps and better parameteriz the age and length of calves at weaning) and health metrics (body condition, growth rates and the energetic cost of reproduction) from a well-studied, easily accessible, reference (undisturbed) population of Blainvilles beaked whales (Mesoplodon densirostris, Md) in Abaco, Bahamas. We will build on a previous study (N000141512748) and document Md growth rates and variability in allostatic load for individuals in this reference population and on a 22-year dataset to determine age at first reproduction and other aspects of parental care. As an optional component of this study, we further propose to investigate Md mating strategies and assess the role that adult males play in calf survival, and as well as the energetic cost of harem defense. We will use aerial photogrammetry and capture-recapture (photo-identification) methods to gather vital rate metrics on Md reproduction, growth rates, body condition and calf survival, and remote biopsy sampling and GT-seq genotyping methods to assess genetic relatedness to investigate Md breeding strategies. Blubber biopsy samples will contribute to an existing study (N000141812778) measuring reproductive and stress hormone levels to document pregnancies from a (disturbed) Md population at the U.S. Navys Atlantic Undersea Test and Evaluation Center (AUTEC), ~170km away from Abaco. Field work will be conducted off Sandy Point, Abaco, where studies of Md have been underway since 1997 and re-sighting rates are high. Using a 6.5 m RHIB, 105 days of field work will take place during the 4-year study, targeting days when weather conditions are optimal for finding beaked whales (sea state 2 or less) throughout the entire year. We aim to collect ~40 biopsy samples from individuals not sampled previously in Abaco (n =29), representing a substantial proportion of the population (parent population is ~150 whales). By conducting field work year-round, re-sightings of females that are known to be pregnant based on photogrammetry morphometrics, will allow us to quantify reproductive success and calf survival, and the energetic cost of reproduction. This study has direct relevance for future monitoring and understanding the population-level effects of disturbance in Navy operating areas; not just for Md at AUTEC, but at other Navy ranges, e.g., Pacific Missile Range Facility. Providing vital rate and health parameters to improve PCoD model predictions for beaked whales is a key step in advancing the Navys mitigation and fleet monitoring strategies. This study will also advance the development of methods for detecting early warning signs of a population decline, such as the population state structure, individual health and growth rates.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Sep 11, 2020
- Source ID
- N000142012756
Entities
People
- Diane Claridge
Organizations
- Office of Naval Research
- United States Navy