North Atlantic Right Whale Energetics in a Changing Environment

Abstract

Critically endangered North Atlantic right whales (Eubalaena glacialis) have low reproductive output linked to poor body condition and nutritional stress. Assessing whether whales meet energetic demands requires quantifying both expenditure and intake under field conditions. This thesis evaluates energetic balance in a summertime foraging habitat during July 2023 and 2024. Daily energy expenditure was estimated using field metabolic rates derived from respiration metrics from biologging tags (n = 23). Energetic requirements increased with age, while mass-specific costs declined. Prey energy density and intake were quantified using zooplankton samples collected near tagged, feeding whales (n = 59). Feeding whales targeted dense aggregations of late-stage Calanus spp., with energy densities 12x higher than background conditions (417 vs. 34 kJ m-3). Estimated intake exceeded daily energetic expenditure by up to 19-fold, indicating that these dense prey aggregations can support energy storage for reproduction and highlighting the importance of fine-scale prey sampling.