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UBC Theses and Dissertations

Energy requirements of grey whales Agbayani, Selina Vivar

Abstract

Eastern North Pacific grey whales (Eschrichtius robustus) rely on energy reserves obtained on their northern feeding grounds to complete their annual 17,000 km round-trip migration between the Arctic and Mexico. However, estimates of how much food is required to complete the annual migration is limited to adult whales of average size, and is not readily available across all age classes of males and females. I constructed an age-structured bioenergetics model using detailed information on the grey whale life cycle and migration timings to predict the energy requirements of different cohorts of grey whales. Results show that nursing calves require 24–35 L of milk daily in their first 9 to 10 months. Once weaned, juveniles require ~345 kg day⁻¹ of benthic invertebrates (4.5% of body weight), while the largest adult whales will need a minimum of ~870 kg day⁻¹ (4.3% of body weight) during the ~5 month (154 days) summer foraging season in the Arctic. In contrast, pregnant individuals need 1,630–1,969 kg of prey day⁻¹ (9.3–10.3% of body weight) during this same period to support foetal growth and store sufficient energy to produce milk once the calves are born in Mexico. Lactating whales returning to the Arctic with their calves will require 1,360–1,960 kg of prey day⁻¹ (8.2–8.9% of body weight) over the next 4.5 months to continue producing milk. My results can be combined with measured densities of benthic prey in the Arctic to assess and anticipate the likelihood of climate change or conspecific competition causing starvation-related mortality of grey whales in the future. My age-structured bioenergetics model is simple and flexible enough to adapt to any migratory species of interest, including rare, endangered species that may otherwise be considered data deficient.

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Attribution-NonCommercial-NoDerivatives 4.0 International