Mar 022008
Authors: Aaron Hedge

For years park officials have juggled a myriad of failed plans to address an overpopulation of elk in Rocky Mountain National Park that threatens the ecosystem and surrounding wildlife.

But CSU researchers might have just what the doctor ordered — birth control.

Ideas to slow or reduce the dangerous elk herd population have ranged from bringing in sharpshooters to the reintroduction of wolves — a natural predator — to the area. But the problem, CSU researchers say, could be solved more easily with chemicals and darts.

Jenny Powers, a CSU graduate student and wildlife veterinarian for the National Park Service, and Terry Nett, associate dean of research and graduate education, along with many other researchers have been working for many years to create a possible method of wild animal birth control.

“The vaccine was created in the 60’s but the one used today originated in the 90’s and we have been modifying it ever since,” Powers said. “The one we use today was last updated in 2006, we have two temporary and one permanent contraceptive.”

The birth control causes a hormone that suppresses ovulation in cow elk by stopping the pituitary gland from performing for almost a year.

One of the temporary birth controls has been found 100 percent effective and lasts one year. The other temporary is only 75 percent effective but can last up to three or four years.

CSU researchers have tested elk in captivity in Fort Collins, focusing on what the negative side effects are.

They are still testing how well it works and what happens to elk that are already pregnant during injection, but their research has not shown any negative side effects so far.

Their research has shown that the female elk injected with the contraceptive are more involved with the bulls during breeding season.

“This is because once pregnant, the female looses interest in the bull,” Powers said. The vaccine does not cause abortion in already pregnant females.

This year Rocky Mountain National Park has administered the contraceptive into 60 female elk in the park, and plan to test 20 elk a year.

“We want to see how they are acting in the wild and to see what the effects are on the elk,” Powers said. “Also to see if they are getting pregnant.”

“The parks are more interested in the temporary birth controls,” Nett said.

Staff writer Ryan Avery can be reached at

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