Noren, S.R.*; Lacave, G.; Wells, R.S.; Williams, T.M.: Development of Blood Oxygen Stores in Bottlenose Dolphins (Tursiops truncatus)

Increased blood oxygen reserves facilitate diving in marine mammals. Previous studies show that pinnipeds require a developmental period for blood oxygen stores to reach adult capacities. We investigated if a developmental period for the blood also occurs in cetaceans which unlike pinnipeds, are exposed to diving immediately after birth. Blood samples were collected from bottlenose dolphins aged 0-12 years from wild and captive populations to determine red blood cell number cell number (RBC), hemoglobin content (Hb), hematocrit (Hct), mean corpuscular volume (MCV), mean cell hemoglobin (MCH), and mean corpuscular hemoglobin concentration (MCHC). We found that during postnatal development, RBC, Hb, and Hct decrease from 0-1.5 months and then increase significantly from 1.5-6 months, reaching adult levels by 3 years. MCV and MCH significantly increase from birth until 2 months of age at which time they approximate adult values. MCHC significantly decreases from 0-3.2 months, then increases and approximates adult values by 6 months. Because weaning occurs at 1.5 years for bottlenose dolphins, the development of the blood oxygen store is not complete with the initiation of independent foraging. The lower oxygen storage capacity of immature dolphins undoubtedly limits dive capabilities as indicated by aerobic dive limits (ADL) calculated from our blood data. ADLs of 0-3 year olds (1.9-4.8 min) are lower than the ADLs of 4-8 and 9-12 year olds (5.1 and 5.4 min, respectively). Increases in ADL from 0 to 3 years are attributed to increases in body mass and mass specific oxygen stores while body mass alone explains the increases in ADL for dolphins 3 to 9 years.