Conservationists look to CSI for elephant counts (Cambodia)
mardi 7 avril 2009
A technique allowing scientists to ‘fingerprint’ elephant DNA from dung samples has revolutionised animal censuses.
Wildlife conservationists have no idea how many wild elephants there are in Cambodia, but as DNA analysis becomes more affordable, conservationists are turning to the same techniques used by crime laboratories to determine Cambodia’s wild elephant population. The main difference from forensic detectives is that conservationists gather their evidence from fresh elephant dung.
The Wildlife Conservation Society (WCS), WWF and Fauna and Flora International (FFI) are all using "fecal DNA capture-recapture surveys", a simple and accurate method to calculate the elephant population that avoids the need to disturb elephants or put humans at risk. The Forestry Administration and conservation groups send trackers to places where elephants are thought to congregate, but instead of looking for the animals themselves, they collect 1-cubic-centimetre samples of elephant dung and place them in a preservative, which are then sent to labs in Australia or the US.
"Our expert officers gather the elephant dung in the forest where they live and are used to exploring. They put their dung in plastic," said Men Phymean, chief of the wildlife protection office at the Forestry Administration. Pamela Jarman, the general manager at DNA Solutions, a company that does the DNA analysis of FFI’s elephant dung, made it clear that the dung itself wasn’t the key to obtaining a DNA fingerprint ; it’s what’s hidden inside. It’s important to use sound science to back up conservation so we can know if we’re being effective.
"We take a dung sample and obtain skin cells from the outer portion of the dung ... the portion that would have rubbed against the digestive system as it passed through, thus hopefully picking up skin cells," she wrote in an email. After the elephants’ DNA is revealed by a lab, a statistical model is used to estimate the number of total elephants based on the amount of individual elephants "captured" multiple times in the samples. For example, if there are 100 dung samples, but they are all from just two elephants, then there are probably only two elephants in the area, but if the DNA analysis reveals the 100 samples come from 85 different elephants, then the population is likely much larger than 85.
"This method is a godsend. Technically, it’s not very complicated," Edward Pollard of the WCS said. The results of WCS’s work in the Seima Biodiversity Conservation Area in Mondulkiri province show the advantages of this new method.
Larger population WCS collected 255 dung samples from 81 elephants, allowing them to estimate a population of 116 elephants, making it one of the largest populations in the region, according to Pollard. "We thought there were maybe 30 or 40 elephants. We were pleasantly surprised," Pollard said, adding that it was a reminder of "how important Cambodia was for global biodiversity". FFI has finished collecting samples from the Cardamom Mountains and received DNA fingerprints but has not finished tabulating the data from its 500 dung samples.
"It could be 50 elephants or 500," Matt Maltby at FFI said. "It’s just so hard to know.... The populations are so remote and dispersed. It’s not like Africa where you can fly over and count." Maltby stressed that these first elephant censuses were only the beginning, and later counts would reveal if the population was increasing or decreasing. "It’s important to use sound science to back up conservation so we can know if we’re being effective.... This will be the baseline point. It’s the start of a lot of work."
As data from around Cambodia comes in, conservationists will also learn about elephant migration. WWF, for example, is currently working in northern Mondulkiri, and if they find some of the same elephants that WCS found in the Seima Biodiversity Conservation Area in southern Mondulkiri, they will know that elephants migrate between those two areas.
Pollard at WCS warns that if elephants are travelling outside the reserves, they could pose a threat to people and their livelihoods if new developments or farms infringe on their migratory track.
"If we know where the elephants are and their range, we can discuss solutions about where and how to farm before human-elephant conflicts occur," he said. Cambodia is in a unique position where - armed with good information - the government and NGOs can help local residents avoid clashes with elephants, he added.
Christopher Shay, Phnom Penh Post April 7, 2009
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