Europe's last wild reindeer are endangered and North America's herds face similar threats from development, conservationists say.

Scientists with the United Nations Environment Program in Arendal, Norway, found a steep decline among Santa's hooved helpers (Rangifer tarandus tarandus).

They say the herd is threatened by the building of dams, mountain cabins and hydroelectric projects in its southern habitat.

Christian Nellemann of UNEP and colleagues say someday both wild and farmed reindeer across the Arctic may face a similar fate.

The researchers surveyed more than 2,000 reindeer between 1977 and 1987, a time of major infrastructure projects in the Norse region.

"Following this development, reindeer densities within a four-km radius declined gradually during winter to eight per cent of pre-development densities," they wrote in the journal Biological Conservation.

The UNEP expects 70 to 80 per cent of the Arctic to be developed by 2050. "Greenland, Canadian, American and Russian reindeer will all be threatened," Nellemann told New Scientist magazine.

In the U.S., caribou, a close relative of reindeer, are listed as endangered.

This week, scientists at Texas A&M University announced they had cloned a deer. They say the fawn, named Dewey, was born in May and appears healthy and normal.

White-tailed deer are abundant in the wild, but the researchers said the cloning technique could prove useful for helping endangered deer species.

Scientists have also cloned sheep, cattle, goats, pigs and a cat.

Biologists have tried importing Canadian and Alaskan caribou to the Selkirk Mountains north of Spokane, Wash., with poor results, wildlife officials said.

Some of the Selkirk animals returned north, others were killed by predators, were poached or died of unknown causes.

Since the 1990s, wildlife managers in the U.S. and British Columbia successfully reduced the number of cougars stalking the mountain herd. They've now shifted their focus to habitat issues.

In winter, reindeer and caribou dine almost exclusively on lichens growing on trees. Logging of old growth forests has limited their diet.

Woodland caribou and reindeer fair poorly when forests are fragmented by roads, according to UNEP.