May 26, 2008

Desert Tortoise Population Dwindles

The Desert Tortoise, which has lived and maintained virtually the same look for over 200 million years, is now dwindling in the southwestern desert of Utah. The population of this fascinating creature has decreased substantially in the Red Cliffs Desert Reserve since 2000. Eight years ago there were an estimated 3,200 tortoises roaming the reserve’s 62,000 acres, and now that number has dropped to 1,700.

A biologist with the Utah Division of Wildlife Resources in St. George, Ann McLuckie, is concerned about the species which spends 95 percent of its time underground. She is fascinated by the tortoise; its shell can span 15 inches across, it bobs its head oddly during courtship, and it makes bizarre hissing, grunting, and whooping noises.

The Desert Tortoise is federally protected and lives predominantly in the Red Cliffs Desert Reserve in Utah’s Washington County, which was established 12 years ago to protect wildlife from human intrusion . The species has benefited from this protection, but has fallen prey to other circumstances.

The Desert Tortoise, although a desert dweller, can only live so long during a drought. When freestanding water dries, the tortoise eats less and tends to weaken, due to their inability to digest food and expel salt.

Other predators such as fires which destroy the primary food sources of the tortoise - cacti, grasses, and wildflowers - threaten their longevity.

Coyotes have also become predators; as recent fires have destroyed their primary food sources, they have shifted their diets to tortoises. According to McLuckie, the Desert Tortoise is feeling the long term impacts of a large fire which spread through the reserve in 2005.

Due to stress from fire and drought, there is a concern that the already-weak tortoises may be more susceptible to an upper respiratory infection, which was first discovered in Utah’s tortoise population in the 1970s. McLuckie says that stress in a population can “exacerbate the disease”.

Roy Averill-Murray, desert tortoise recovery coordinator for the U.S. Fish and Wildlife Service in Reno, Nevada, is especially concerned with the mortality rates in the Red Cliffs area. In the past, it was seen as a stronghold for the Desert Tortoise, but its density has decreased and mortality rates have increased in the past few years.

Bringing more tortoises to the area has been informally proposed, but keeping track of the animals can be difficult due to the percentage of time they spend underground. Tracking devices are affixed to some of the tortoises. Averill-Murray claimed, "We know they can live 60 years in the wild and even longer in captivity. They can even live longer than the researchers studying them."