July 8, 2011

Pig-Nosed Turtle Population Declining

Researchers have discovered the population of pig-nosed turtles has declined over the past 30 years.

The turtles have become an international conservation icon, due to it having no close relatives and being considered the turtle most adapted to life underwater in freshwater ponds and rivers.

The reptile faces a threat in Papua New Guinea because of a high demand for its eggs.

"Pig-nosed turtles are considered unique and unusual among freshwater species of turtles in many facets of their morphology, ecology and behavior," Carla Eisemberg of the University of Canberra, Australia, told BBC Nature.

The team said embryonic pig-nosed turtles become male or fame depending on the temperature of the ground their eggs are laid in, while fully developed embryos can delay their hatching.

The turtle is the sole survivor of a family of turtles called the Carettochelyidae and is only found in north Australia and New Guinea Island.

The researchers said that the turtle might represent a stage of gradual evolution of turtles from freshwater to the sea.

"Similar to marine turtles, its limbs are paddle-shaped, but still possess movable digits," said Eisemberg.

"On the other hand, the similarities they share also make it vulnerable to the same threats that marine turtles face, such as harvesting of nests and adults," Professor Eisemberg told BBC.

The researchers surveyed the numbers of eggs and adult turtles nesting in the Kikori region of Papua New Guinea.  Elsemberg and colleagues also studied how many turtles and eggs passed through local markets and were consumed in villages along rivers and the coast.

Scientist Mark Rose, now at Fauna and Flora International in Cambridge, UK, and a member of Professor Eisemberg's team, conducted a similar survey of pig-nosed turtle population between 1980 and 1982.

This study allowed scientists to compare how the turtles population has declined over the past 30 years.

The evidence suggests that turtle numbers have fallen, but "we provided, for the first time, concrete evidence of a substantive decline in these pig-nosed turtle populations," Eisemberg told BBC.

The team found that villagers harvested over 95 percent of monitored nests.  Female turtles have also become smaller on average, and bigger individuals have been removed from the wild population and the overall life expectancy of the species has fallen.

The team found that over 160 adult female turtles had been harvested in the study area.

Overall "we estimated the decline in this pig-nosed turtle population to be more than 50% since 1981," Eisemberg told BBC.

"Such a decline is likely to be widespread as the species is under similar pressures elsewhere in Papua New Guinea," she added.

"Highly prized as food, it is the most exploited turtle in New Guinea. Both turtle and eggs are collected for trade or consumption by local villagers.

"The pressure on pig-nosed turtle populations has increased in recent years, especially in Western Papua and Papua New Guinea."

According to the scientists, conservation plans to save the turtle are need, and it will take decades for the pig-nosed turtle to recover.

However, these plans must be made sensitively, as the communities in New Guinea living in pig-nosed turtle habitat often rely on protein from the reptile to survive.

"We need to provide win win outcomes to both local and conservation communities," Eisemberg told BBC.


Image Caption: Young specimen of the Pig Nosed Turtle in captivity in Slovakia. (Credit: Faendalimas/Wikimedia Commons)


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