Meeting Abstract

13.8  Friday, Jan. 4  Ontogeny of oxygen storage capacity and diving ability in southern sea otters (Enhydra lutris nereis) THOMETZ, N.M.*; WILLIAMS, T.M.; University of California, Santa Cruz ; University of California, Santa Cruz nthometz@ucsc.edu

As the smallest members of the smallest marine mammal species, immature sea otters face extraordinary physiological challenges as they transition from dependent pups to independent foragers. High energetic demands and limited oxygen stores severely limit the diving ability of a variety of immature marine mammals, potentially impacting their ability to respond to changes in prey distribution and abundance. We examined the ontogeny of blood and muscle oxygen stores and calculated aerobic dive limit (cADL) in southern sea otters. Key blood and muscle parameters, including hemoglobin (Hb), hematocrit (HCT), red blood cell (RBC) count, mean corpuscular hemoglobin content (MCHC), and myoglobin (Mb) content were determined for pups, juveniles in their first year post-weaning, and adults. Pups had oxygen stores between 69-89% of adult values depending on size and age, while juveniles had oxygen stores similar to adults. Neonates displayed minimal Hb levels (11.76±0.36 g/dL) which increased in large pups (15.78±0.32 g/dL) and juveniles (18.13±0.35 g/dL). Mb levels were particularly low in neonates (0.31±0.15 g/100g tissue) and medium pups (1.24±0.30 g/100 g tissue) but reached adult levels in juveniles (3.4±0.14 g/100g tissue). Small and medium pup cADL was between 1.0-1.9 minutes, while large pup cADL ranged from 2.1-2.9 minutes. Despite similar oxygen storage capacity, juvenile cADL was only 2.7-3.6 minutes compared to 3.0-4.1 minutes for adults, due to increased metabolic demands. As benthic foragers, limited aerobic capacity will likely impact the ability of young otters to compete with adults for limited food resources.