Dolphins bottle up our fascination

Friendly, playful bottlenose dolphins always have fascinated people, especially since the 1960s TV show “Flipper” made the warm-blooded marine mammals famous.

The average person, however, probably doesn’t realize how much researchers value the creatures, says Dr. Teri Rowles, coordinator of the Marine Mammal Health and Stranding Response Program at the National Oceanic and Atmospheric Administration (NOAA) in Silver Spring.

“It’s pretty amazing the amount of information you can get from one of these animals,” she says. “We use them as sentinels of the marine environment.”

Bottlenose dolphins, large animals with slightly hooked, broad dorsal fins, interest the scientific community for many reasons. They are frequently examined by researchers to simply learn more about the species. In addition, scientists use them to study pollutants and diseases in the ocean. The mammals also have been trained by the U.S. military for wartime procedures.

Dr. Rowles, who is a veterinarian and holds a doctorate in toxicology, says researchers in her department routinely perform necropsies on dead bottlenose dolphins that wash onto beaches. These procedures are similar to human autopsies, where the cause of death, such as infection or cancer, is better analyzed.

During necropsies, scientists try to learn information such as the age of the animal’s sexual maturity, its reproductive condition, what parasites may have infested it and what it has been eating. The creature’s age is determined by counting the growth layers in their teeth.

Although more evaluations need to be completed before a broad spectrum of conclusions can be drawn from the studies, scientists have been able to make some preliminary conjectures.

For instance, it seems the amount of pollutants in male bodies increases with age as they continue to eat contaminated food, while females eliminate pollutants through their milk, which is passed to offspring. The specific pollutants carried by the animals are identified through testing portions of blubber.

Live-capture examinations complement the tests associated with beach strandings, says Aleta Hohn, leader of the cetacean and sea turtle team with the NOAA Research Laboratory in Beaufort, N.C. Ms. Hohn, who holds a doctorate in biology, often works with Dr. Rowles.

“The more we look, the more we find new things about the animals,” Ms. Hohn says. “We’re looking more carefully now than we used to look.”

While examining living animals, technicians record their size and weight. To test for diseases and pollutants, they also take samples of blood, urine, feces and blowholes. For instance, the blood tests reveal which animals carry the antigen for the Moribillivirus that killed a large number of bottlenose dolphins on the East Coast in 1987 and 1988.

Unfortunately, research shows only a small number of dolphins have been previously exposed to the disease. Therefore, if a new outbreak were to occur, there probably would be another mass epidemic.

Researchers also frequently attach tags, which stay intact for about 10 months, to the dorsal fins of the mammals during live-capture examinations, Ms. Hohn says. This allows scientists to track their migration cycles through a satellite system.

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