By ELAINE VAINA
MUSSAU Island in New Island lies 160 kilometres north of Kavieng and is well known for having a large population of green turtles.
However, recent surveys by the Wildlife Conservation Society (WCS) have found turtle densities around the island to be highly variable. Two villages, Nae and Lolieng, are separated by just 33 kilometres of coastline but have very different turtle densities.
For example, the reef crest at Lolieng supports an average of 7 turtles per hectare whereas the same habitat at Nae has only 0.2 turtles per ha.
Azalea Anota, a research intern at WCS working on the turtles describes the situation.
“Not only are the number of turtles between the two areas very different but so is their behaviour.
Turtles in Nae have been persecuted for various reasons and not surprisingly their numbers are much lower, and as a result the turtles in this area also have adopted very specific behaviours not seen in the other community such as only coming into the lagoon area at night when there are fewer people around”.
The disappearance of sea grass beds and an edible seaweed species (known locally as “goru”) has made locals concerned with many suggesting the turtles are to blame.
Nathan Whitmore, a scientific officer with WCS, is doubtful of the connection.
“Actually scientific evidence suggests the reverse, namely that green turtles, actually help to maintain healthy seagrass beds. In fact, we know die offs of green turtles have been directly linked to the death of seagrass beds around America.
“We shouldn’t forget that according to Mussau locals the number of turtles was already dropping at the very same time the lagoons started to lose seagrass and goru.”
Anota, who is leading research on the turtles elaborates, “At this stage we are looking at the seagrass and goru decline from a number of different perspectives including the possible impacts from the increased irregularity of the north-west monsoon, whether the depth of the lagoons has decreased due to uplift caused by earthquakes, as well as human impacts on goru harvesting, turtle populations, and reef health.”
Nathan Whitmore adds, “Green turtles are disappearing from the world’s oceans but it is clear that the sea around Mussau Island can still support large numbers of turtles today. For this reason the area is of regional significance not just in PNG but Melanesia. But at this stage the future of the turtles is not guaranteed.”
The Wildlife Conservation Society is currently working with the local communities to understand the relationship between Green turtles, people, seagrass and goru in a two year project funded by the Critical Ecosystem Partnership Fund.
- The author is Media Officer at Wildlife Conservation Society.
The Green Sea Turtle
THE green sea turtle (Chelonia mydas), also known as the green turtle, black (sea) turtle, or Pacific green turtle, is a large sea turtle of the family Cheloniidae. It is the only species in the genus Chelonia.
Its range extends throughout tropical and subtropical seas around the world, with two distinct populations in the Atlantic and Pacific Oceans, but it is also found in the Indian Ocean.
The common name comes from the usually green fat found beneath its carapace; these turtles’ shells are olive to black.
This sea turtle’s dorsoventrally flattened body is covered by a large, teardrop-shaped carapace; it has a pair of large, paddle-like flippers. It is usually lightly colored, although in the eastern Pacific populations parts of the carapace can be almost black. Unlike other members of its family, such as the hawksbill sea turtle, C. mydas is mostly herbivorous. The adults usually inhabit shallow lagoons, feeding mostly on various species of seagrasses.
The turtles bite off the tips of the blades of seagrass, which keeps the grass healthy.
Like other sea turtles, green sea turtles migrate long distances between feeding grounds and hatching beaches. Many islands worldwide are known as Turtle Island due to green sea turtles nesting on their beaches. Females crawl out on beaches, dig nests and lay eggs during the night.
Later, hatchlings emerge and scramble into the water. Those that reach maturity may live to eighty years in the wild.
C. mydas is listed as endangered by the IUCN and CITES and is protected from exploitation in most countries. It is illegal to collect, harm or kill them. In addition, many countries have laws and ordinances to protect nesting areas.
However, turtles are still in danger due to human activity. In some countries, turtles and their eggs are hunted for food. Pollution indirectly harms turtles at both population and individual scales. Many turtles die after being caught in fishing nets. Also, real estate development often causes habitat loss by eliminating nesting beaches.