Abstract
As health care and husbandry continue to improve for marine mammals in managed collections, the number of geriatric animals has increased.1 Due to the increasing number of older dolphins at the Navy (nearly 10% of the population during 2007 was older than 40y), a geriatric health program was initiated with goals to 1) decrease 5y mortality rates for dolphins 30–40y old to that of younger age classes, and 2) ensure the highest quality of life among Navy marine mammals for the longest period of time. As part of this program, a retrospective study was conducted to assess normative, physiological changes as animals aged from 30 up to 50 yrs.2 Hematological and serum chemistry data generated from routine, fasted blood samples collected over 10 to 20y among six dolphins that lived at least 40y were analyzed to assess linear trends in blood variable values with increasing age; compare mean blood values by older age categories (30–35y, 36–40y, and > 40y); and compare the prevalence of clinically relevant blood values (above or below normal reference ranges) by older age categories. Absolute lymphocytes, serum globulins, and mean platelet volume increased linearly with increasing old age. As dolphins aged, mean white blood cells, neutrophils, serum globulins, erythrocyte sedimentation rates, serum cholesterol, and serum triglycerides increased. The prevalence of neutrophilic leukocytosis, hyperglobulinemia, and hypercholesterolemia was also more likely to increase as geriatric dolphins got older. A linear decrease in serum albumin with increasing age was present for five of six animals. Serum creatinine decreased among dolphins older than 40y compared to when they were 30–40y old. Our study demonstrates that older dolphins can have evidence of chronic inflammation, sarcopenia, and hypercholesterolemia with routine samples, similar to that found in older humans. Further studies are needed to assess whether these changes are associated with negative health outcomes and whether targeted therapeutics can help improve the quality of life among aging dolphins.
Acknowledgments
The authors thank the U.S. Navy Marine Mammal Program's veterinary care staff, records office, and management for supporting the marine mammal preventive care program that enabled this long-term study.
References
1. Venn-Watson S, Jensen ED, Ridgway S. Population health indicators of the Navy Marine Mammal Program bottlenose dolphin (Tursiops truncatus) population, 1988–2007. J Am Vet Med Assoc 2011; 238: 356–360.
2. Venn-Watson S, Smith CR, Gomez F, Jensen ED. Physiology of aging among healthy, older bottlenose dolphins (Tursiops truncatus): Comparisons with aging humans. J Comp Physiol B 2011; DOI 10.1007/s00360-011-0549-3.