News>Desert tortoises get 'head start' to survival
The desert tortoise is officially listed as "threatened" under the federal endangered species act. Environmental Management workers adopted the Head Start Program here to help bolster the population of younger age class tortoises to adult ages. (Air Force photo by Senior Airman Stacy Sanchez)
Edwards established the Head Start Program to give desert tortoises a better chance of survival at a young age, The Head Start Program was created four years ago. (Air Force photo by Senior Airman Stacy Sanchez)
by Senior Airman Stacy Sanchez
95th Air Base Wing Public Affairs
5/14/2008 - EDWARDS AIR FORCE BASE, Calif. -- As part of Edwards effort to increase the desert tortoise population, people from Environmental Management here established the Head Start Program.
The Head Start Program, started four years ago and located in the southern central portion of Edwards, is designed to bolster the population of younger age class tortoises to adult ages.
"The desert tortoise is officially listed as threatened under the federal endangered species act," said Mark Hagan, Environmental Management natural resource manager. "The decline in the population has been so drastic to the point of becoming endangered."
Urbanization, off-road vehicles and major highways put stress on the desert habitat causing the decline of the tortoise population, Mr. Hagan said.
To help young tortoises survive, the Head Start Program built five tortoise pens to protect them from predators.
"We have put up these pens to help protect (tortoises) during their early life stage," Mr. Hagan said. "When we feel that they are at the stage where they can survive on their own, we can release them back into the desert. Hopefully, this will give them a better chance of survival."
The hatchery process begins with the collection of 20 adult females out in the desert, Mr. Hagan said. To keep track of their location at all times throughout the year, radio transmitters are put on the tortoises. During the spring time, when female tortoises start laying eggs, they are weighed, X-rayed and brought to the pens to lay their eggs. Once the females tortoises have laid their eggs, the adult tortoises are taken back to the location from where they were found.
Of the five pens built, three are for healthy tortoises while the other two pens are for ones that show signs of disease, Mr. Hagan said. Currently, the tortoises in the pens range from 1 to 4 years old.
Edwards adopted the head start studies from Fort Irwin, Calif. -- the first base to begin the Head Start Program and hatchery, he said. As a federal agency, the Air Force has a requirement to help restore and recover endangered species, such as the desert tortoise.
Since the inception of the Head Start Program, EM workers have been studying the age group that will have the greatest chance of survival.
"There are a few phases to the Head Start Program," said Amber Bruno, an Environmental Management natural resources biologist. "Not only are we looking at what rate a young tortoise should be released out into the wild, (but) we are also looking to see if providing supplemental irrigation to their pens can enhance the growth rate of the tortoises and shorten the time that is needed for the tortoises shell to harden."
Over the last four years, two batches of tortoises were released back into the wild. They were released in the fall to mimic their natural cycle. When the first group of 15 1-year-old tortoises were released, subsequent studies showed the tortoises were susceptible to predators -- primarily ravens.
In 2007, another 32 tortoises were released -- some near the pens, while others at a remote location.
This is to see if there is a significant difference when they are released on various location, Ms. Bruno said.
"The data is still preliminary, but we have found that 1-year-old tortoises are still not big enough to resist predators." she said.
Also discovered, she said, is that tortoise eggs are prone to predators such as the antelope ground squirrel and fire ants.
Since the beginning of the project, tortoises here have laid 395 eggs; 190 of which have hatched.
"However, there is not a lot of data for the hatch rate of tortoises in the wild," Ms. Bruno said. "When we are out in desert environment, it is almost impossible to find tortoise nests with eggs.
"Now, we have the advantage of knowing where the females made their nest, laid their eggs and the number of eggs that hatch," she said. "On base, we are now experiencing more than a 75-percent hatching rate. This is really good."
Environmental Management is also studying the paternity of the tortoises.
"We look at the genetic and reproductive studies here," Mr. Hagan said. "Genetics is important in species management. We have done a paternity study of the paternal relationship of tortoises, and what we have found is that all female tortoises have multiple mates. Almost 90 percent of the nests here have multiple fathers."
Knowing the different aspect of the reproduction while managing a species is important, he said. This helps give a genetic diversity to protect the species through time.
"This project is showing a lot of promise," Ms. Bruno said. "We are learning a lot here, and if we apply this program, it may serve to help recover a (threatened) species and allow the tortoise to survive and increase in population."
Team Edwards can do their part to help desert tortoises by being aware of the environment they are in, Ms. Bruno said.
People should be aware of the impact they may have on the environment, she said. They must stay on the trails when they are off-roading and when found, tortoises must be left alone.
"The Air Force is hoping to test the technology and the techniques here and refine them," Ms. Bruno said. "Once the team learns more and can prove that this program works, it can be relayed to other federal agencies such as the Bureau of Land Management. On a regional approach throughout the desert, organizations can also start more of these head-start locations to recover the desert tortoise throughout its range."