Health Assessments of Common Bottlenose Dolphins (Tursiops truncatus): Past, Present, and Potential Conservation Applications

Abstract

The common bottlenose dolphin (Tursiops truncatus) is a global marine mammal species for which some populations, due to their coastal accessibility, have been monitored diligently by scientists for decades. Health assessment examinations have developed a comprehensive knowledge base of dolphin biology, population structure, and environmental or anthropogenic stressors affecting their dynamics. Bottlenose dolphin health assessments initially started as stock assessments prior to acquisition. Over the last four decades, health assessments have evolved into essential conservation management tools of free-ranging dolphin populations. Baseline data enable comparison of stressors between geographic locations and associated changes in individual and population health status. In addition, long-term monitoring provides opportunities for insights into population shifts over time, with retrospective application of novel diagnostic tests on archived samples. Expanding scientific knowledge enables effective long-term conservation management strategies by facilitating informed decision making and improving social understanding of the anthropogenic effects. The ability to use bottlenose dolphins as a model for studying marine mammal health has been pivotal in our understanding of anthropogenic effects on multiple marine mammal species. Future studies aim to build on current knowledge to influence management decisions and species conservation. This paper reviews the historical approaches to dolphin health assessments, present day achievements, and development of future conservation goals.

Keywords: Tursiops truncatus; conservation; dolphin; health assessment; veterinary medicine.

Figure 1

Bottlenose dolphin capture-release health assessment locations in the U.S.

Figure 2

Capture methodology with (A) seine net deployed from a specially designed boat creating a compass in the center of the image, with chase boats circling outside to help contain the animals before completion of the compass and to deliver handlers to the net (two dolphins are visible inside the compass on the left side). (B) Shallow water set, well-trained handlers distributed around the circumference of the compass to provide aid and restraint when the dolphins contact the net. (C) Deep water set, dolphin is placed onto a floating mat and disentangled from the net for transport to the processing vessel. All photos taken under NMFS MMPA/EAS permit No. 18786-03.

Figure 3

Ultrasound examination of a lymph node on board the veterinary examination and sampling vessel (MMPA ESA Permit No. 18786-03).

Figure 4

Blood sample collection from the peri-arterial rete on the ventral aspect of the tail fluke (MMPA ESA Permit No. 18786-01).

Figure 5

Exhaled breath sample collection for cytology (MMPA ESA Permit No. 18786-03).

Figure 6

ECG leads attached during sampling and processing to closely monitor the dolphin's heart rate and assess cardiac function (MMPA ESA Permit No. 18786-03).

Figure 7

Dolphin suspended in a stretcher for weight measurement via load cell on board the veterinary processing vessel. This image was published with permission of MMPA ESA Permit No. 18786-01 for the identifiable individuals in the image.