SPINNER DOLPHINS

Dolphin Research Project

The first day on Midway Island the researcher explained the goals of the spinner dolphin research project was to determine habitat use, the abundance and distribution of dolphins,  group size and composition, social structure of the dolphin schools, social affiliation patterns between individual dolphins, to develop a photo-identification file for the dolphin population and develop year-round baseline activity patterns.

Such information will impact the development of boat usage in the atoll. The aim is to disturb the dolphins as little as possible in order to keep them in the area and not to disturb them enough to leave. Is the population  transient or residential? Do sub-groups exist and if so how stable they are.

No research/documentation had been done yet on dolphins in an atoll habitat. Midway is a perfect place for such a study as the shallow clear waters of the lagoon allow for detailed observation below the water as well as above it.

Spinner dolphins, Stenella longirostris, receive their name from the frequent activity of leaping from the water and spinning in the air. Apparently spinning is done solely for fun but, it may also serve as a signal that feeding is about to begin. It is significant that spinning activity peaks in mid-afternoon before the group spreads out at dusk to forage for dinner. Aerial activity is used in socialization and is believed also to be used in communication. Some scientists speculate that aerial activity also serves to remove ectoparasites from the dolphin bodies.   Spinners can reach a height of about 3 meters when they spin and can make a maximum of four revolutions. Spinner dolphins swim mostly in deep waters, but occur in regions where there are shallow platforms or islands.

The schools of dolphins on Midway are larger than those around the other Hawaiian Islands, very likely because there are fewer sheltered land and resting areas. There is a large shark population in the area so the lagoon provides a safe and quiet place to rest. They typically live in tropical waters, but may range into temperate water with a worldwide distribution.

The average spinner is 5 ½ -6 ½ feet long. Calves at birth are generally 30 inches long weighing 33 pounds. Gestation is 10 ½ months and females will lactate for a period of 1-2 years. Typically, males are bigger than females. Female spinners sexually mature between 4-7 years and tend to have one ovulation  period each year. Males mature later, usually between 7-10 years. Mating is promiscuous with peak activity during summer and fall. Lifespan for spinners is about 20 years. Only 1% of females have been documented to reach post-productive status. Although spinner dolphin society is highly promiscuous, family units are apparent.

Contact is an essential ingredient in spinner dolphin society where touching, nuzzling, and stroking occur frequently among the animals in the group even though the composition of the group changes. Many dolphins are day feeders, but spinners feed at night in deep waters on fish, squid, and shrimp. They have been documented to dive to depths of 200-300 meters while feeding.

For most dolphin species the dorsal fin is used for identification because it can be photographed from the surface of the water. Nicks and marks in the trailing edge of the fin are most often used for identification because they are relatively permanent and change little over time. 

We used a 23 foot pontoon boat for water surveys which were conducted at random in five transects of the lagoon. It was great fun to watch the dolphins bow surfing with us. The schools sometimes contained some small animals.

This was a fun 10 days to say nothing of being educational and interesting.

SOME MIDWAY ISLAND HISTORY

Three  Great Weeks on Midway Island 

      
           I went to Midway island to help on a couple of research projects and to be a travel companion with a friend. Much to my surprise it turned out to be a fantastic three weeks.   Several foreign nationals have lived on Midway for years. The Thais keep the water system running and the Sri Lankans are the mechanics and carpenters.

            Midway Atoll is 1250 miles northwest of Honolulu, just north of the Tropic of Cancer and east of the International Dateline. The atoll is part of the Hawaiian archipelago but is not part of the state. It consists of three low coral and sand islands with a total land mass of 1600 acres. In 1988 the atoll was designated Midway Atoll National Wildlife Refuge and is now managed by the U S Fish and Wildlife Service.

            The Service has strict guidelines which include a required briefing when you learn all visitors are to stay on paved walkways/ roads and designated trails, and some areas are strictly off limits. The air facility operationally closed in 1993. In 1996 President Clinton gave US Fish and Wildlife jurisdiction of Midway. At the time of my visit, Oceanic Society Expeditions was the exclusive tour operator for Midway working closely with USFWS to realize goals of protecting and preserving fish, wildlife, and historic resources. Several research projects have been conducted at the atoll.

The BOQ our hotel for three weeks

            Not long after my visit (just before the turn of the century) Midway was shut down to tourist because of damage to the ecosystem. Now visitation is possible on a very limited basis through a handful of eco- friendly tour companies.

            All infrastructure is on Sand Island which is 1.8 miles long and 1.2 miles at its widest point.  Besides housing, there is a gym, weight room, basketball court, billiards, bowling, tennis courts, library, carpenter shop, transportation shop, and other necessary maintenance buildings, and a new modern medical facility.

            Eastern Island has no structures left except the overgrown runway. Accessible only by boat (we used a WWII era landing craft) to visit.  Visitation to that island is limited to small guided groups.. Spit Island is tiny, has no significant history and is strictly a bird refuge. The few vehicles on Sand Island are for work and maintenance only. We did have golf cart transport available to us for classes, but generally we walked or rode a bike. This was not a hardship!

            A fun tidbit: The last Easter and New Years services/celebrations in the world occur on Midway. If one crossed the International Date Line, 140 miles away, he could attend the first celebrations, then fly back to Midway and attend the last ones.

The tallest point on the island is the 165 foot water tower. All fresh water is obtained by catchment, stored in three huge tanks, sent through two treatment systems, and then pumped through a system to all faucets.  In the era of 3000 residents on Midway water had to be barged in. Today water is not a problem; there is plenty and water pressure is good.

            Midway was the first off-shore island to be annexed by the US in 1867 under the Guano Act. Since there are no bird rookeries on Midway the collection of guano would have been a tedious, nearly impossible task. However, history would prove this to be a most strategic move.          

In January 1903, in response to complaints of Japanese squatters and poachers, President Teddy Roosevelt placed the atoll under the control of the Navy. That spring the Commercial Pacific Cable Company arrived on the island. After the Navy removed the squatters and poachers they appointed the Cable Company  the island custodians. On July 4, 1903, from this station, President Teddy Roosevelt sent the first around-the-world cable which took nine minutes to complete.

            Pan Am set up a base for its Clipper Seaplane Service on Sand Island in 1935. Midway was a regular fuel stop for Pan Am’s Trans-Pacific route which included Honolulu, Wake Island, Guam, and Manila. This operation, including a hotel and restaurant was short lived—only 1935-1941. The US Naval Air Station Midway was commissioned in August 1941.

Many people do not realize that on December 7, 1941 in addition to the bombing of Pearl Harbor, Midway was also shelled. The hospital was demolished as well as half of the hanger. One fuel tank was hit and smoldered for days, but it served as a beacon for returning US pilots. The communication center took a shell wounding the operator and  temporarily knocking out the whole system.  Lt. George Cannon sustained a crushed pelvis but refused to leave his duty station until communications were restored. Then he was bodily removed by his men, but he later died, having bled to death. He was the first Medal of Honor recipient of World War II.

There is much more to tell about this fantastic visit, but this enough for today.

Birds Everywhere

GOONIES

When I arrived at Midway Island , 1200 miles across the Pacific Ocean from Hawaii, I knew nothing about a gooney bird other than people thought they were a crazy bird  They got their nickname from the often crazy landings they make, but they are actually the Laysan Albatross. Rather awkward on land, they are beautiful and graceful in flight.

The gooney bird mates for life, and every late October/early November returns to the same spot to wait its mate’s return. With a 6 ½ foot wing span they weigh 7-8 pounds. Unlike other albatross who feed during the day, the Laysan gooney is a night feeder. Albatross are synchronous breeders. As seabirds, they live and feed at sea. A small hole on each side of their beak allows the bird to excrete salt.

Mama lays a single ½ pound egg in early December. Dad immediately begins to incubate the egg while Mama goes to sea to feed for a couple of weeks. When she returns to take over the sitting duties, Dad leaves to feed. This alternating behavior goes on for 60 days, until the chick hatches.

It takes both parents to raise the chick. If one parent dies, the chick dies. Both parents continue to alternate going to sea to feed the chick. A chick taps the beak of the parent to stimulate regurgitation, then places its beak inside that of the parent catching every single drop. The chick is ready to fledge at 5 months and goes to sea for 3-5 years before returning to find a mate of his own.

Twenty percent of the chicks die before fledging and 7-10 % of the fledging chicks are eaten by tiger sharks that come into the lagoon during fledging season just for that reason. The oldest known tagged bird is 43 years old. It is unusual for birds to mate in winter, but the Midway summer is very hot and it is difficult for the birds to stay cool. Their webbed feet are very vascular and the birds thermo-regulate through them by sitting on the backs of their feet with the webbed toes off the ground.

The mating ritual is fascinating to watch. The gooney makes many different noises. The most common are the clacking of their beaks and sky pointing called sky mooing--- and they really do sound like a cow.