One bite of the tempting bran-like pellet -- and she's lost an opportunity to be a mother.

The pellets containing a specially developed contraceptive and abortion drug have been spread around northwest China's Gurbantunggut Desert in a bid to control a destructive plague of gerbils.

Staff in desert administration station in Changji City, Xinjiang Uygur Autonomous Region, started to feed gerbils tailor-made drug during the main breeding season in May 2008.

"Besides pregnancy prevention, the drug can induce abortions, and thus largely reduce their breeding rate," said Du Yuefei, chief of the epidemic prevention section under the city's forestry bureau.

The gerbils pose a major threat to agriculture and horticulture as the rodents store grass in complicated burrows that seriously damage the root stalks of plants. One such hole can store 40 kg of grass.

Instead of spreading the pellets on sites frequently haunted by gerbils, Du's colleagues put them at the burrow entrances.

"It's a good way to tackle the desert rat plague," said Du.

The low-toxic drug has little effect on other animals, and the gerbils have no resistance to it, and so it keeps the biological chain intact.

Du said the project could be extended to deal with other rodent problems in northwest China.

"The only problem is that our 20 or so staff have to redistribute the pellets every four to five days, and it's really hard work," said Du.

Numerous burrows can be seen all over China's northwest region, especially in Xinjiang and Inner Mongolia. The rodents tend to burrow on the lee side of slopes. A medium-sized burrow group usually contains dozens of small holes, while a large one has up to 300.

Du said his section spent 80,000 yuan (US$11,400) of 200 kg of the drug, which covered 49,000 hectares last year.

Du and his colleagues have noticed that population density has started to decline.

"Before we used the contraceptive, we caught 12 gerbils in every 100 rattraps, but since the average has been 11 in every 100 traps," said Du.

Changji City set up the desert ecology preservation station in 2003, and installed 300 perches for owls and eagles, both natural enemies of rodents, said Meng Jijin, head of the north station.

He noticed the number of gerbil holes has dropped since the contraceptives were put in the desert.

Gerbils multiply quickly and a female can give birth to a litter every three months.

(Xinhua News Agency March 25, 2009)