Postpartum Development of Blood Oxygen Stores in Bottlenose Dolphins (Tursiops truncatus): Effects on Calculated Aerobic Dive Limits

S.R. Noren¹, R.S. Wells²,³, and T.M. Williams¹
¹ Department of Biology, University of California at Santa Cruz, Santa Cruz, CA 95064
²Department of Ocean Sciences, University of California at Santa Cruz, Santa Cruz, CA 95064
³Chicago Zoological Society, c/o Mote Marine Laboratory, Sarasota, FL 34236

During foraging, marine mammals undergo prolonged breath-holds by relying on enhanced body oxygen stores. Previous studies show that pinnipeds require postpartum development for oxygen stores to reach adult capacities. Unlike pinnipeds, cetaceans dive immediately after birth. We show that dolphins still require postpartum development of blood oxygen stores. Blood samples were collected during captures of wild bottlenose dolphins of known age in Sarasota, Fl.. Red blood cell number, hemoglobin content, and hematocrit increases from 1-3 years of age; the one year age class has significantly lower values than many older age classes (p < 0.05). Consequently, aerobic dive limit (ADL) calculations show reduced dive capacity for young dolphins. ADLs of 1, 2, and 3 year old dolphins (3.2, 3.6, and 4.8 min, respectively) are lower than ADLs of 4-8 and 9-12 year olds (5.1 and 5.4 min, respectively). Increases in ADLs for 1-3 year olds are attributed to increases in body mass and mass specific oxygen stores while body mass alone explains the increases in ADLs for animals >3 years. For example, total mass specific oxygen stores increase from 22 mlkg¯¹ to 24 mlkg¯¹ from one to two year olds but levels off at 30 mlkg¯¹ for animals > 3 years. Previous reports suggest that weaning for bottlenose dolphins occur at 1.5 years old, thus we demonstrate that development of the blood is not complete with the initiation of independent foraging. Therefore, it is likely that the lower oxygen storage capacity of immature dolphins influences their diving capabilities and hence foraging behaviors.

The collection of the blood data was made possible through funds provided to R.S. Wells by Dolphin Quest and The Chicago Zoological Society. Travel for S.R. Noren was made possible through funds provided by the Alan Baldridge Grant from the American Cetacean Society, Monterey Bay Chapter awarded to S.R. Noren and an ONR grant awarded to T.M. Williams.