Assessing nutritional stress and pregnancy in Blainville s beaked whale at the Atlantic Undersea Test and Evaluation Center (AUTEC)
Abstract
Studies at the U.S. Navy s Atlantic Test and Evaluation Center (AUTEC) in the Bahamas indicate that Blainville s beaked whales (Mesoplodon densirostris, Md) move away from Navy sonar sources and are displaced from their regular feeding habitat. Bioenergetics models suggest that beaked whales require relatively high-quality habitat to meet their energy requirements, and that regular displacement from preferred feeding habitats could potentially impact survival and reproduction through compromised body condition. This is of particular concern for pregnant and lactating females that have increased energetic demands. Recent findings of low reproductive success of Md at AUTEC have led to a hypothesized population consequence of repeated disturbances. However, empirical data on female body condition and growth of calves is lacking, constraining a direct assessment of whether nutritional stress from disturbance is a realistic mechanism for explaining the apparent population responses. We propose to combine photogrammetry, photo-identification and blubber hormone measures to examine nutritional stress and pregnancies in Md at AUTEC with these objectives: aerial photogrammetry will be used to measure width profiles to directly assess individual body condition and detect pregnancy, and ground-truth inference about nutritional stress from hormone measures (cortisol and thyroid hormones, T3 and rT3), comparing adult females with (lactating) and without dependent young; hormone-derived identification of pregnancy (progesterone and testosterone) will be used to ground-truth photogrammetric inference based on body shape; and aerial photogrammetry will be used to compare state-specific size (total length) and body condition (width profiles) of whales at AUTEC to a reference population to investigate size differences as a potential indication of longer term nutritional stress. Photogrammetry measurements and blubber biopsies will be linked to individuals with known life histories, based on the pattern of natural scars discernible from the air and boat platforms. Field teams will operate at AUTEC during good weather windows over the course of each year (15 days in FY18, 30 days in FY19, FY20, and FY21), and scheduled as close as possible after submarine commander s courses to capture any physiological or nutritional stress responses that may be associated with disturbance during these multi-day events. Over the 4-year study, we aim to collect photogrammetry data with matching biopsy samples form 70 individuals, focusing on adult females. Multiple visits to the field site will enable follow up resightings of females known to be pregnant based on hormone measurements and photogrammetry morphometrics, allowing us to quantify reproductive success and calf survival. To comply with U.S. regulations, the Navy must ensure that testing and training does not negatively affect annual rates of recruitment and survival of potentially impacted populations. By understanding how changes in adult female body condition relates to successful pregnancy and calf growth rates, we can better predict how foraging disruption during sonar testing will affect reproduction and calf survival. Using the proposed combination of photogrammetry, life histories and hormone measures, we will document pregnancy success rates in Md at AUTEC while determining the covariate underlying reproductive success. Testing and establishing nutritional stress as the mechanistic link between disturbance and population consequences in beaked whales is a key step in developing mitigation strategies, and validation of these techniques is important for use on future fleet monitoring.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Sep 04, 2018
- Source ID
- N000141812778
Entities
People
- Diane Claridge
Organizations
- Office of Naval Research
- United States Navy