Bruce Boyd stood in the meadow of Bimbo ski run flanked by Ponderosa pines and a bevy of biologists. The sun beat down on this open patch where wildflowers bloomed beneath a deep-blue sky at the 8,830-foot elevation.
They caught a fleeting glance of an orange sulfur butterfly and the flash from a couple of Carole's silverspots. But swarms of winged insects that would normally flutter over the wildflowers on this warm, late-July morning were nowhere in sight.
"We should have seen hundreds of butterflies," said Boyd, an expert observer whose chronicles are cited by agencies that monitor native butterfly populations on Mount Charleston and throughout the Spring Mountains.
"This is not just a boom and bust of an individual species," said Boyd, a slim, mustached man who has hiked the Lee Canyon meadows many times.
"This is more ominous. We are potentially seeing a shift in the fauna and habitat. Do we have statistical evidence of that? No."
Boyd had ventured to the meadows on Wednesday hoping to see a rare Mount Charleston blue butterfly. Just one confirmed sighting of a dime-size Mount Charleston blue would have made his day.
Even though federal biologists determined that the iridescent Mount Charleston blue butterfly warrants protection afforded by listing it as a threatened or endangered species, the U.S. Fish and Wildlife Service decided to preclude the action in March. Instead the agency deemed it a candidate for listing because it is only a subspecies of Mount Shasta blue butterflies, and there are higher priorities for listing other plants and animals that are more imperiled.
Boyd said that doesn't bode well for some 40 native species of butterflies in the Spring Mountains, of which nine are endemic, or found nowhere else on the planet, including the Mount Charleston blue.
"We use butterflies as environmental indicators of the health of the environment they're in," he said.
"Obviously something has gone seriously awry. ... There's a major event shift occurring that's way beyond the Mount Charleston blue. It was the first 'canary,' if you will, to get sick in the coal mine."
BRINK OF EXTINCTION
Coincidentally, federal scientists are on the mountain the same day on an orientation trip because of the Las Vegas Ski & Snowboard Resort's expansion plans.
The resort's general manager, Kevin Stickelman, said the U.S. Forest Service's acceptance of the master plan in mid-July marks the beginning of the approval process that will determine which projects will require full environmental assessments.
"It's going to be years to get some of these projects through the planning process, 10 to 12 years," Stickelman said.
Their orientation trip came in the aftermath of a landmark agreement reached July 12 between the service and the Center for Biological Diversity, a group dedicated to species preservation. The pact will spur the agency to make decisions on adding more than 750 plants and animals to the list of federally protected species, including the Mount Charleston blue butterfly and 53 other species in Nevada.
In March, the service issued a 65-page finding, which cited Boyd's observations that the Mount Charleston blue teeters on the brink of extinction.
He has noticed the decline over the past 10 years. The Mount Charleston blue held its ground for decades after it was first documented on the mountain in 1928. It had been recorded off and on at 15 locations, with the last significant sightings at some of those locations in 1995.
In the late 1990s, Boyd walked a relatively narrow survey route in the upper Lee Canyon meadows and counted 67 Mount Charleston blues in that stretch alone.
The numbers dropped significantly over the next 10 years. In a July 2010 survey, biologists found the blue at only two locations: a wilderness area along the South Loop Trail above Kyle Canyon, where 17 were sighted, and in Lee Canyon at the Las Vegas Ski & Snowboard Resort, where a single adult blue butterfly was observed.
A number of factors are suspected culprits in the apparent population decline including drought, fire suppression and human activities that caused the loss of habitat.
HORSES AND HABITAT
But Boyd believes the timing of the decline coincides with another so-called "human" activity: allowing feral horses to graze in the meadows.
The horses, he said, sidestepping a pile of dung, have been "a major impact."
To understand why, consider the blue butterfly's life cycle. For a few weeks in midsummer adults fly low over the meadows to mate. The females lay eggs and a few days later the eggs hatch. Pinhead-size caterpillars, or larvae, emerge and feed on what's called a host plant, in this case a small, low-growing herb called Torrey's milkvetch. The milkvetch prefers sunny, open areas at elevations between 7,500 feet and 10,800 feet.
That's one reason the resort's backers argue that maintaining open areas in the ski area might, in fact, enhance the butterfly's chances of survival.
The caterpillars grow to about one-quarter of an inch in a couple weeks and then form pupae, which lie dormant on the ground in leaf litter, or duff. After a year, or maybe even two winter seasons, they open up as the ground warms. Adults then fly out, starting the cycle again.
Boyd said horses tromping around to graze in the meadow might have affected the butterfly's habitat. They seem to have left an ample supply of milkvetch, though.
"There's more plants than could ever be eaten (by larvae) so there's something else occurring."
He pointed to another possible factor: the Forest Service's thinning of trees at lower elevations to suppress forest fires and using chippers to dispose of branches and small trunks, and then spreading the chips over soil.
That might have prevented generations of pupae from emerging or disrupted their dormant stage.
BOOM AND BUST
Fish and Wildlife biologist Corey Kallstrom noted that animal populations, especially insects, go through periods of boom and bust. But, he said, more studies need to be completed on Mount Charleston blue butterflies to better understand why the population seems to have tapered the past 10 years.
"Right now we do know the population is very low," Kallstrom noted.
While there were only 18 sighted in last year's surveys, more probably exist outside the survey area, which only "gives you a pulse on the population," he said.
The Fish and Wildlife Service biologists in cooperation with colleagues at the Forest Service and the University of Nevada, Las Vegas are in the second year of a three-year study of life patterns and behaviors of the Mount Charleston blue butterfly.
"It will be a guide on how to better manage the landscape," Forest Service spokeswoman Judy Suing said.
"We found out quite a bit from the survey but we don't have any concrete conclusions at this point," she said. "There are so many factors to consider. One of the obvious ones is climate change."
Suing said the Forest Service did consider potential impacts from thinning trees for fire suppression. The service gave guidelines for chipping downed trees and branches to the contractors who did the work.
There was at least one case in a Lee Canyon campground where a contractor spread chips on the ground beyond what was authorized.
"So the Forest Service went out with wheelbarrows and rakes and removed the chips," Suing said. "They were scattered in other locations."
Contact reporter Keith Rogers at krogers@review journal.com or 702-383-0308.