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Endangered Amargosa voles return to Mojave Desert

SHOSHONE, Calif. — The Davis Dozen is on the loose.

Shortly after sunrise Friday morning, 12 endangered Amargosa voles raised at the University of California in Davis were set free in the waist-high grass at a spring-fed marsh near the tiny town of Tecopa, about 90 miles west of Las Vegas.

It marked the first release of captive-bred voles into the wild since the rare rodent was added to the endangered species list more than 30 years ago.

A group of bleary-eyed members of the Amargosa Vole Team celebrated with coffee and a hard-earned nap.

Brian Croft is acting division chief for the U.S. Fish & Wildlife Service in California’s Mojave Desert. He came out to observe the release and wound up as one of four people who camped out at the marsh with the voles Thursday night.

Croft said breeding the animals in captivity and releasing them into the wild has been part of the agency’s recovery plan since the 1990s, and now it’s finally happening.

“It’s really a momentous thing for us,” he said.

INTO THE DESERT

The operation began Wednesday in Davis, where team members loaded their test subjects into cages for the 500-mile-plus drive to a mobile home in Shoshone they would use as their bunkhouse and staging area.

On Thursday morning, the collection of veterinarians, biologists and graduate students gathered around the dining table to prep the voles — six males and six females, including four mated pairs, all roughly the size of a cardboard toilet paper tube and ranging in age from about 6 months to a year.

Each animal was placed in a zippered plastic bag and weighed before being injected with a small identification chip known as a PIT tag just under the skin behind its head.

“It’s the same thing you give dogs and cats and criminals, only smaller,” said UC Davis veterinary professor Janet Foley, co-leader of the species recovery project.

Eight of the test subjects also were injected with tiny doses of anesthetic to knock them out long enough to be fitted with radio tracking collars weighing less than a nickel.

The collars will allow the research team to track the voles’ movements until the batteries die in about three months — or the animal gets eaten.

Foley said “everything” preys on the dark-brown rodents, including coyotes, bobcats, owls, egrets, falcons, snakes, bullfrogs and even the occasional house cat.

But the biggest threat to the species is habitat loss. The Amargosa vole is only found in a handful of marshes east of Death Valley, where it survives on an exclusive diet of heat-loving bulrush that greens up as the temperature rises to 120 and beyond.

Over the past three years, drought and human disturbance led to the destruction of most of the rodent’s core habitat around Tecopa, prompting emergency collection of 20 juvenile voles in July amid concern the species could disappear in as little as a year.

Those voles have been breeding at UC Davis ever since, building a captive colony that now includes about 60 animals. Foley expects that number to double by year’s end, depending on the success of Friday’s operation and another pilot release planned later this summer.

BABIES ON BOARD

One of the first voles prepped Thursday was a beefy 6-month-old male that topped the scales at well over 100 grams.

“He’s one of the largest males we’ve made,” said a proud Risa Pesapane, the UC Davis graduate student who runs the captive breeding program.

“He’s just a handsome specimen of voleness ready to go out and find a wife,” Foley added.

As she examined another animal a short time later, a smile spread across Foley’s face. “She’s pregnant,” the veterinarian said.

Doing some quick math in her head, Pesapane guessed this surprise litter would arrive within the next week or two, the first of many wild-born voles the team hopes to produce.

“I want this to be successful because I don’t really want to own a zoo of Amargosa voles,” Foley said later. “I want to see them recovered out here.”

At dusk Thursday the voles were transferred into wire cages placed in the marsh two months ago so they could spend the night getting used to the sights, sounds and smells while safe from predators.

Four members of the team camped out nearby to keep watch on the cages, sleeping in shifts so at least two people were on sentry duty at any one time. Foley said a few coyotes came around during the night but were chased away with a flood light.

At about 6:10 a.m. Friday the cage doors were opened so the voles could begin exploring their new home. Within a few hours, several of the animals had ventured into the surrounding marsh.

For four members of the Davis Dozen, the release was a homecoming. They were among the 20 juveniles hastily captured in July.

Since then, Pesapane said, the four “originals” have paired off and mated, producing three or four litters each. They are now back in the wild in a different, better-quality marsh than the one where they were born.

The team plans to document the voles’ movements for at least the next week and to return in a month. The animals will be tracked and trapped regularly for genetic and disease testing and to “check for babies,” Foley said.

“That’s the million-dollar question with one of these captive-bred voles,” said Deana Clifford, a California Department of Fish and Wildlife veterinarian and Foley’s co-lead on the recovery project. “Will it breed with a wild vole that’s already out there in that marsh?”

A GAME OF INCHES

This is by no means the only vole work underway.

Foley said scientists at the University of California, Berkeley are performing genetic comparisons of the captive and wild populations, while a researcher at Purdue University assembles a detailed map of the species’ DNA.

“We’re going to have an Amargosa vole genome in a month,” she said.

Meanwhile, efforts are underway to restore and expand existing marshes in the area and to create new habitat on nearby public and private land. That work is being led by another UC Davis graduate student, Stephanie Castle, whose knowledge of bulrush and her success cultivating it has earned her the nickname “vole lunch lady.”

It’s literally a game of inches. On Thursday afternoon, Castle stopped to inspect the plants and water at what was once the area’s largest and lushest marsh. The sudden loss of this habitat is what prompted last year’s emergency capture of juvenile voles.

Castle hopes to restore the marsh to its former glory by slowly raising the water level an inch or two at a time to spur new growth without drowning voles still there.

Though the exact population is unknown, there might only be a few hundred Amargosa voles left in the wild.

They were first collected and described by naturalists in the late 1800s, but habitat destruction by early settlers led scientists to declare the animal extinct in the early 1900s.

The rodent was rediscovered in the late 1970s and listed as endangered by the state of California and the federal government in the early 1980s.

The Amargosa Vole Team originally planned to release 29 voles in April, all of them captive bred, but that operation ended in disaster when all but three died in their cages during the trip from Davis. Researchers later determined the voles probably were killed by a combination of heat, dehydration and stress.

The team took a host of precautions this time around, including transporting the voles in larger cages surrounded by circulating fans and temperature gauges. To avoid the daytime heat, they made the roughly 10-hour drive at night.

They arrived in Shoshone before dawn Thursday morning, exhausted but ready for a happy ending.

Contact Henry Brean at hbrean@reviewjournal.com or 702-383-0350. Find him on Twitter: @RefriedBrean

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