LOOKING FOR DOLPHINS

Bottlenose Dolphins

            Each day in Belize we went looking for dolphin in different locations. Our team was lucky as we found these beautiful creatures every day!  We used a 23-foot boat with a 75 horse power outboard engine and took turns documenting various data.

            When we spotted dolphins we counted the number of animals and the composition of the pod as well as their behavior. We followed them as long as possible noting the beginning and ending times of the sighting. Dolphins are identified by their dorsal fin. In the evening we had a chance to help identify various dolphins---not an easy task!

Because there are no year-round residents at Turneffe Atoll the human impact on the ecosystem and dolphin is minimal. The government owns a few small fishing camps on the atoll which are leased to licensed fishermen who fish mostly for lobster, conch, snapper, grouper, and barracuda. Gill netting and purse-seining are illegal in Belize, so all fishing is small scale.

The mangroves serve as nurseries for baby fish and invertebrates. They are a nutrient source for the sea grass beds which trap sediments from the mangroves. Clear water is essential for the health of the reef. Corals need light to grow and the reef is home to a multitude of fish.

Bottlenose dolphins inhabit temperate and tropical waters throughout the world. There appear to be two ecotypes: an off shore and a coastal form. They can be identified by skull and teeth structure and by blood characteristics.

            Coastal bottlenose dolphins vary in group size ranging from one individual to 30 animals. These animals stay within a limited home range although they may migrate hundreds of miles. The home range of coastal populations may overlap. The offshore ecotype can be observed in larger groups. Atlantic bottlenose dolphins are generally 6-9 feet long and weigh between 136-272 kilograms. They receive their name from their bottle-shaped beak. Their body resembles a torpedo. The coloration ranges from gray to almost black. In warmer climates they exhibit a pink belly when engaged in rigorous activity as a way of releasing heat.

Males reach sexual maturity between 10-12 years; females at 5-12 years. Gestation is 11-12 months and calves nurse 12-18 months.  Females give birth to a single calf. Long term studies show that their lifespan can be 40-50 years. Age is determined by growth layers in a dolphin’s tooth. (Similar to counting the rings on a tree) Bottlenose dolphins are active predators that feed on a wide variety of fish and invertebrates.  In many areas they have adapted their feeding habits to coincide with human activities. They are often seen feeding behind fishing boats and shrimp trawlers. At Turneffe the main activity is lobster and conch fishing.

Bottlenose dolphins are often seen bow riding and body surfing and this may be a means of reducing energy expenditure by allowing the wave motion to carry them forward. However, they also will surf on a wave that takes them in the opposite direction of movement and may suggest that this is a form of play behavior.

Dolphins are highly social and are usually seen in schools.  It has been suggested that learning within the social unit is important and that school behavior is a major component of the animal’s daily activity regime.

Dolphins are mammals and must breath to survive. Unlike most mammals they have no hair but an insulating layer of fat to maintain a constant body temperature of 97-99 degrees. The porpoise is a close relative of the dolphin, but has a blunt snout and a stockier build, not quite as sleek 

This was my first research trip and whetted my appetite to do several other such projects. It was a  fun, learning and active vacation!