SCIENCE NOTEBOOK

SCIENCE NOTEBOOK

A new study suggests that conservation efforts have helped populations of the endangered green sea turtle grow in some places by perhaps 14 percent per year.
A new study suggests that conservation efforts have helped populations of the endangered green sea turtle grow in some places by perhaps 14 percent per year. (Caribbean Conservation Corp)
Monday, December 31, 2007

Green Sea Turtles Reemerging

Endangered green sea turtles are enjoying a slow but steady recovery at six major nesting grounds, according to a new analysis going back 30 years. The findings suggest that conservation efforts are pulling the large reptiles back from the brink of extinction.

The majestic swimmers, which grow to three feet long and can weigh more than 300 pounds, are found in the Atlantic, Pacific and Indian oceans and are important players in sea grass ecosystems. For centuries they have been exploited for their meat, decorative shells and the eggs they lay on beaches; and by mid-20th century, several populations were extinct or nearly so.

Because the turtles spend years foraging at sea, it is difficult to measure population sizes and trends. So scientists from six major nesting sites in Japan, Hawaii, Australia, Costa Rica and Florida collaborated in an analysis of how many females had returned to lay eggs at their respective sites over the past 25 to 30 years.

Those numbers have steadily increased, at 4 to 14 percent per year, the team reports in the December online issue of the journal Global Ecology and Biogeography. Doing particularly well are the turtles that nest at the Archie Carr National Wildlife refuge on Florida's east coast: They were almost extinct in 1980 but their numbers have grown 14 percent per year since 1982.

At one rookery -- the largest, on Australia's Great Barrier Reef -- population increases have recently flattened, suggesting that problems may be reemerging or that the population has achieved its natural maximum.

Extrapolating from the rookery counts, which tally only the nesting females in a population, the team estimates that the six areas account for tens of millions of green sea turtles worldwide.

-- Rick Weiss

Male Chimps Stay Close to Home

Male chimpanzees in the wild -- even the alphas who can go wherever they choose -- generally stay close to where they were born and where their mothers taught them to find food. Researchers had thought that male chimps would be more inclined to roam in a search for mates, but a new study in the Gombe Stream National Park in Tanzania found that it appears that food often trumps sex.

"We have found that, like females, male chimpanzees have distinct core areas in which they forage alone and to which they show levels of site fidelity equal to those of females," said Anne Pusey of the University of Minnesota, an author of the study in the journal Current Biology. "Moreover, males remain faithful to the area in which they grew up with their mother, even 20 years after she has died."

The researchers, who analyzed "space use" by male chimps for more than four years, compared those ranges with the known paths their mothers had traveled. Chimps are not known as a strictly territorial species that stays in well-defined areas -- especially because a male's reproductive success depends on the number of females with which he can mate -- so the results were something of a surprise.

"Our study shows that male site fidelity persists for years after the mother has died and probably for the whole life of the male," Pusey said.

The team plans to continue research on Gombe chimps to determine whether the males really do find food more efficiently in familiar areas and whether the chimps learn particular diets from their mothers.

-- Marc Kaufman


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