Each winter, rangers at Pt. Reyes National Seashore train guns on the park's deer to thin herds. But soon they may be firing contraceptive darts at some of the animals instead of bullets.
Park Supt. John Sansing said park officials are considering an offer by In Defense of Animals, a national animals-rights' group, to pay $1,400 for a pilot program to temporarily sterilize 15 female tule elk.
The females belong to a herd of 240 elk that threatens to overgraze its 2,600-acre home at Tomales Point, Sansing said.
The tule elk merit special consideration because they are natural to the park--unlike the axis and fallow deer rangers have killed at the rate of 50 a year since the mid-1970s, said Bill Shook, a resource-management specialist for the park.
"Hunting, as far as we're concerned, is a dead issue," Sansing said.
Sansing is inviting wildlife management and reproductive specialists to study the use of the darts. He said chances of a trial are good.
The panel, headed by UC-Berkeley professor Dale McCullough, also plans to review other forms of birth control for animals, such as "bio-bullets" that release contraceptives into muscle tissue.
No matter what the panel recommends, Sansing said a decision on the darts wouldn't be reached before November.
And because the elk usually mate in early summer, it would take another year before the trial could begin, Shook said.
The darts contain an immuno-contraceptive called porcine zona pellucida, made of the clear protein material surrounding a pig's egg. The chemical enters the bloodstream and prevents pregnancy. The darts fall off after releasing the chemical.
Zoos worldwide have been using the darts on baboons, lions, giraffes, bison and other species for 15 years, said Jay Kirkpatrick, a wildlife contraceptive expert with the Deaconess Research Institute in Billings, Mont.
Deer held captive at a secret location in Ohio, because of opposition from hunters, have been temporarily sterilized at a rate of 100% for the last four years, said Kirkpatrick, who will be on the panel.
Since 1988, the darts have been used to treat wild horses at Assateague Island National Seashore off the coast of Maryland with a 95% success rate, Kirkpatrick said.
He said the birth control does not present a threat to hunters because of hunting bans at national parks.
The National Institutes of Health is sponsoring the wild horse study with an eye toward possibly using the contraceptive on humans someday, Kirkpatrick said.
Tule elk were reintroduced to the park in 1979. The herd grew at a rate of 13% last year, and has increased by as much as 17%, Shook said.