Bighorn move toward recovery; reintroductions expand species back into historical range
The recovery of the endangered Sierra Nevada bighorn sheep took one more step forward last month with the California Department of Fish and Wildlife’s second reintroduction effort since 1986.
In late March, they translocated 14 bighorn to a remote part of Sequoia National Park, which has been devoid of bighorn since the early 20th century.
“It was such a huge milestone to get these [bighorn] sheep into the Kern,” said biologist Tom Stephenson, program leader for the Sierra Nevada Bighorn Sheep Recovery Program.
The Sierra Nevada bighorn sheep were given emergency endangered status in 1999 after their numbers hit an all-time low of 100 in 1995.
This new herd near the Big Arroyo region of Sequoia National Park will be an important reservoir of bighorn due to its geographic isolation from the Eastern Sierra populations, he said.
The Department has wanted to reintroduce bighorn to Big Arroyo for over three decades, Stephenson said, “but we didn’t want to do anything to harm the source populations.” The overall population just wasn’t big enough to support reintroduction, he said.
Source herds must be stable enough to donate 10 ewes, which scientists have determined to be a sufficient number to start a new herd.
March 2013 marked the first successful reintroduction of bighorn since 1986 to an area near Olancha.
In addition to last month’s reintroduction of 10 ewes and four rams to the Big Arroyo region in Sequoia National Park, the Department also augmented the Olancha herd with four females.
The Olancha herd now has 15 ewes, three rams, and an undetermined number of lambs.
Though it’s a tough job, the project has been very successful with reintroductions, said Ben Gonzales, wildlife veterinarian for the department.
“It’s complicated,” he said, “because of the politics of endangered species work in a fairly agricultural area.”
How to relocate a bighorn sheep
In mid March, Stephenson and his team began capturing bighorn from the Wheeler Ridge herd near Bishop. From a helicopter, the team netted the bighorn, then hobbled and blindfolded them, and carried them one-by-one to a processing site.
Once hobbled and blindfolded, they’re remarkably calm, said Stephenson.
Gonzales and his team provided the equipment and expertise at the processing site. At the site, they fit collars to the animals so they can track them, and take samples to test for disease, look at nutrition, and determine pregnancy status.
Then they loaded the bighorn into one of several big aluminum boxes to be carried south by a pickup truck.
Another helicopter picked up the aluminum boxes and carried them to the remote release site, where Stephenson and biologist Alex Few were waiting.
When they opened the boxes, Stephenson said, some of the bighorn burst out at a full sprint. But others didn’t want to leave and just hung out in the box, he said—so they had to go in and pull them out.
The hard work is far from over with this latest reintroduction. To monitor the new Big Arroyo population, scientists will have to hike 25 miles just to find the bighorn.
Scientists still have to monitor populations from the ground, because as populations grow, they won’t have collars on every bighorn. Additionally, if data from the collars indicates a bighorn has died, they have to hike in to find out what happened, regardless of season.
In the winter, Stephenson said, avalanches can wipe out a lot of bighorn.
In the most recent example, six bighorn in the Wheeler herd were wiped out in an avalanche in Scheelite Canyon near Bishop, popular among backcountry skiers and known (in the warmer months) among rock climbers for Pratt’s Crack.
Two more sites await reintroductions, one near Taboose Creek and the other near Laurel Creek.
Stephenson said he hopes the Taboose site will be recolonized naturally.
Laurel Creek is their next priority, and they will continue augmenting herds in order to increase genetic diversity, grow the populations, and replace lost animals.
After over a decade spent augmenting herds, Stephenson said, “we’re finally able to reintroduce new herds to completely meet the recovery goals.”
And that recovery, he said, could happen in as little as a decade.