Dive Performance and Aquatic Thermoregulation of the World’s Smallest Mammalian Diver, the American Water Shrew (Sorex palustris) (original) (raw)

ABSTRACTAllometry predicts that the 12–17 g American water shrew (Sorex palustris)—the world’s smallest mammalian diver—will have the highest diving metabolic rate coupled with the lowest total body oxygen storage capacity, skeletal muscle buffering capacity, and glycolytic potential of any endothermic diver. Consistent with expectations, and potentially owing to their low thermal inertia, water shrews had a significantly higher diving metabolic rate in 10°C (8.77 mL O2 g−1 hr−1) compared to 30°C water (6.57 mL O2 g−1 hr−1). Unlike larger-bodied divers, muscle myoglobin contributed minimally (7.7–12.4%) to total onboard O2 stores of juvenile and adult water shrews, respectively, but was offset by high blood O2 carrying capacities (26.4–26.9 vol. %). Diving was predominantly aerobic, as only 2.3–3.9% of dives in 30 and 10°C water, respectively, exceeded the calculated aerobic dive limits at these temperatures (10.8–14.4 sec). The mean voluntary dive time of water shrews during 20-min...