Researchers believe that 500 or more bottlenose dolphins spend their summers in the Roanoke and Croatan sounds, and that as many as 10,000 pass through Outer Banks waters during their winter southerly migration.

This makes the Outer Banks a critical point for observing and studying bottlenose dolphins. But until recently they weren't being studied here, and if a marine mammal was stranded on the coast of the Outer Banks, there was no local person to get to it quickly.

Today, two different groups are funneling information on the Outer Banks' dolphins into an East Coast network of researchers intent on learning more about the playful creatures.

The 3-year-old Nags Head Dolphin Watch researches live bottlenose dolphins in the Roanoke and Croatan sounds from May through November. The National Marine Fisheries' Marine Mammal Stranding Network, based in Beaufort, contracted with its first Outer Banks employee this year, ensuring a much quicker, and therefore more informative, response to marine mammal strandings.

After more than 740 bottlenose dolphins died on the East Coast in 1987, several independent research groups sprung up from New Jersey to Florida to gather basic background information on the animals. Before then, the only group studying bottlenose dolphins was an independent group in Beaufort. At the time, National Marine Fisheries proposed a study on bottle-nose dolphins, but it was so expensive it never got off the ground.

In 1993 about 20 independent research groups banded together to form the Atlantic Dolphin Research Cooperative to gain a better understanding of the dolphins' migratory patterns and habits. Working together and comparing photographs of the dolphins' dorsal fins, each of which is different, the groups from up and down the East Coast began to match dolphins between research areas.

But there was a huge gap: the Outer Banks of North Carolina.

In 1997 Rich and Kate Mallon-Day from Pennsylvania filled the gap by starting Nags Head Dolphin Watch. Rich Mallon-Day had been studying dolphins and marine mammals off Cape May, N.J., before coming here.

The Mallon-Days and their assistant, Kristen Mazzarella, are conducting a long term photo identification study of the bottlenose dolphins and providing a base for dolphin research operations on the Outer Banks.

While other independent research groups are funded by museums or state and federal grants, the Mallon-Days looked for a way to creatively fund their studies to avoid competing with other research groups for money. Nags Head Dolphin Watch funds its extensive research solely through ticket sales for a boat tour that takes tourists on dolphin watching trips from May through September.

In its first summer, Nags Head Dolphin Watch made a critical discovery. It was the sighting of a bottlenose dolphin named Onion, a known winter resident of the Beaufort area. Onion, whose propeller mangled fin makes him easily identifiable, was the first dolphin for whom researchers knew both the winter and summer residence.

Since then, the Mallon-Days and Mazzarella, in conjunction with Beaufort research teams, have identified about 65 bottlenose dolphins that summer here and winter off Beaufort.

Nags Head Dolphin Watch does its research by taking photos of the dorsal fins of every dolphin seen on every trip. Each dolphin has a distinctive dorsal fin recognizable by its shape, color or permanent notches and nicks. Researchers name the dolphins with monikers such as Onion, Honey Mustard, Butterfly, Jesus, White Tipped Shark, Fatlip and Hangover.

``When you see them often enough, you begin to recognize them right away,'' said Mazzarella. ``It's a lot easier to call out a name than a number.''

Nags Head Dolphin Watch has a photographic catalog of the fins of more than 260 dolphins. The photos can be seen online at www.dolphin-watch.com. On the site, there's also a monthly contest to name a dolphin. Last month's winner was Hitchcock.

Mallon-Day said that photographing and networking is very important because it is turning up many matches. For instance, this summer he spotted a familiar fin in Nags Head waters. After comparing photos of fins with other groups, Mallon-Day learned it was Spike, a dolphin he had seen previously in New Jersey.

The Nags Head Dolphin Watch catalog will become part of a National Marine Fisheries effort to combine and organize the photos and research from all of the Atlantic Dolphin Research Cooperative photo collections into a computerized catalog. National Marine Fisheries also does an annual capture and health assessment of live dolphins in one or two locations.

``That research is critical for learning more about the health of dolphins,'' said Mallon-Day. ``We can only tell where they are and who they hang out with, but nothing about their physical health.''

While Nags Head Dolphin Watch has learned a lot about the bottlenose dolphins in this area, it has also discovered that the animals are unpredictable. Sometimes the group finds pods of up to 150, but sometimes they just see two swimming together. On average, they see pods of 15 to 20.

The dolphins have no regular swimming patterns but follow their food supply - croaker, pinfish, spot, silver perch - so finding them is not always easy. The Nags Head Dolphin Watch boat depends on the help of fishermen and another dolphin watch operation in Manteo run by Stuart Wescott.

In September, when dolphin watch tours are over, the Mallon-Days return to their home in Pennsylvania, and Mazzarella continues to search for dolphins for about another month. After that, most of the dolphins in the sounds have gone south. Mazzarella also travels to Beaufort to compare her photographs with those of the crews there.

Mazzarella has not seen dolphins here since Oct. 26. The first dolphin sighting in 1999 was Onion on May 21. In 1998, the last sighting was on Oct. 31. A few days later, that dolphin was sighted in Beaufort.

Up until now, because of the logistics of operating a tour boat six days a week in the summer, the dolphin watch has studied only the dolphins in the Croatan and Roanoke sounds. But in the upcoming year, Mallon-Day said he hopes to fund one tour boat and one research boat so that they can cover more ground, especially into the ocean, and try to follow pods of dolphins for entire days to see where they go and what they do. Mallon-Day believes that some, but not all, of the dolphins he sees in the sounds are sometimes seen in the ocean.

The Marine Mammal Stranding Network, based in Beaufort, is also an important contributor in the research on bottlenose dolphins. This group responds as soon as possible to any marine mammal stranding, whether it's a dolphin, porpoise, whale or seal.

With the hiring of its first Outer Banks contractor, Karen Sayles, to cover the areas from just south of Virginia Beach to Ocracoke, the group will be able to respond more quickly to strandings. In the past, a researcher would have to drive three hours from Beaufort after a stranded animal sighting. By then, much of the most important data would be lost.

January, February and March are the peak migration seasons for marine mammals through this area, so more strandings happen during this time than any in any other. When a stranded marine mammal is sighted in this area, the report first goes through Beaufort, but Sayles is the first person to respond and perform a necropsy of the animal.

During the necropsy, Sayles tries to determine the cause of death and collects samples of tissue, blubber, muscle and teeth. The teeth determine the age of the animal, and the blubber can reveal any contaminants the animal has been exposed to. She also examines the organs and the stomach content of the animal. If the animal is a bottlenose dolphin, Sayles alerts the Nags Head Dolphin Watch group so that they can look at the fin to see if it's one of the dolphins they've been tracking.

Sayles' necropsy samples are sent to various places for research. Much of the sample material goes to Beaufort, some goes to Duke University, and the skull is sent to the Smithsonian Institution.

Since she started her position a month ago, Sayles has performed necropsies on two bottlenose dolphins, one in Duck and one in Southern Shores. The cause of death on both animals was inconclusive, though Sayles said the one in Southern Shores appeared emaciated and sick.

Sayles encouraged people who might see her performing a marine mammal necropsy to stop and ask questions.

``I'd rather people ask than just walk by and always wonder what we were doing to that animal,'' said Sayles. ``It may look disturbing, but it's a valuable learning opportunity.''