Research Objectives:
Freely diving Weddell seals in Antarctica offer a unique opportunity to follow the biochemistry and physiology of nutrient utilization in a large carnivore.
A study of the in vivo nutritional biochemistry of foraging in a free-ranging, large mammalian carnivore has never been attempted because of the logistics of obtaining multiple blood samples, conducting turnover studies, and measuring digestive chemistry while the animal is actively foraging. Although such studies can be conducted in laboratory or zoo settings, they are limited to captive animals whose feeding times and diets are typically constrained by humans.
A unique opportunity exists in the Antarctic. For several decades, the Weddell seal has been the focus of natural diving physiology studies using isolated holes through the sea ice near McMurdo Station. The seal has access to a single ice hole where it routinely returns to breathe, sleep, digest, and so on. With the use of blood-sampling catheters, this group has been able to collect serial samples whenever the seal returns to the surface between dives. During such experiments, these seals actively catch and digest their prey. However, all previous studies have focused on diving physiology per se because they were designed to examine how the animals tolerated long periods of holding their breath. Any observations on nutritional chemistry were incidental and not part of the study design.
This season, researchers will take this method in a new direction by examining how Weddell seals process nutrients while foraging. Like all seals, Weddell seals rely primarily on lipid metabolism for daily energy. Therefore, this group will examine the kinetics of lipid uptake and utilization during active foraging bouts. They will obtain blood samples from freely diving animals and use labeled traced experiments to quantify lipid turnover rates and separate the lipid pool into its various components. They will also compare lipid uptake and utilization in adult seals and in pups, which are biochemically adapted for massive and rapid lipid utilization while nursing.
This project will provide important insights into mammalian biochemistry. These data will be important not only to antarctic ecosystem studies, but also to the entire field of lipid metabolism in mammals and the study of carnivore biology.
