Gila monsters -- poisonous, colorful, reclusive and a bad guy in a classic Western movie -- are dying off in Utah because of headlong growth and development in St. George and the rest of Washington County.

The lizards must not go extinct and need federal protection, says WildEarth Guardians, a Southwestern conservation group that is blanketing the U.S. Fish & Wildlife Service (FWS) with petitions and lawsuits aimed at fending off biological annihilation. The group also recently sued to get a relatively unknown Utah snail on the federal endangered-species list.

It's all part of an eight-week action, dubbed BioBlitz, that follows years of dogging the feds, whose steps to protect animals and plants have slowed to a crawl, says Nicole Rosmarino, WildEarth Guardians' wildlife-program director and policy analyst.

"One of the major issues today is the majority of endangered species in this country aren't protected," she says. "It is about protecting the whole web of life."

On Friday, FWS received WildEarth's petition to list the Gila monster on the endangered list. Scientists agree that southern Utah roads, dogs, cats and rampant urban growth are killing the colorful lizards.

The Utah Division of Wildlife Resources has a plan to keep them off the list, says Krissy Wilson, the agency's native aquatic program coordinator.

If FWS deems urban development too great a threat to Gila monsters, the state has a year to counter the finding by showing its protection efforts are working.

Generally, states argue they can manage their native species better than the federal government. "[State] government folks do not want anything listed," Wilson says. "But it may be there's nothing you can do about it. ... Maybe it has to be listed."

That would put the Gila monster -- featured in a memorable scene in the 1948 movie, "Treasure of the Sierra Madre" -- in the same league as the desert tortoise, listed as an endangered species in the early 1990s.

Conservationists, Washington County officials and others created the 60,000-acre Red Cliffs Desert Reserve north of St. George to protect tortoise habitat. Most of Utah's Gila monsters live there, as do sidewinder rattlesnakes, chuckwalla and peregrine falcons, also rare and sensitive species.

The state needs more such reserves, Rosmarino says, along with better planning to "provide buffers for nature in our midst."

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Unintended consequence » WildEarth Guardians, which operates on a sleek budget with a membership of 4,500, taps established science and information posted on the respected online clearinghouse NatureServe to buttress mass and individual petitions and lawsuits against FWS.

The agency, beset with scandal under the Bush administration and rebuked last year in a Government Accountability Office audit, has more than 300 species on a list of candidates for federal protection. There, they languish, Rosmarino says, and can die out before FWS arrives at decisions.

"We don't like to be in this position to prompt them when species are imperiled," she says. "Really, we're doing their job. They shouldn't be fighting us."

But the tactic slows the business of an already-strapped agency, says FWS spokeswoman Valerie Fellows.

Fifteen years ago, she says, the Fund for Animals sued the agency to list 400 species already named as candidates. FWS had to set aside its work on critical habitat to do so. In 1996, the budget was halved. Soon afterward, the agency faced a lawsuit over its lack of work on critical habitat.

The resultant court order meant FWS had to ramp up designating critical habitat for more than 400 species. Meanwhile, the lawsuits and petitions continued to flow, including one from WildEarth that sought protection for more than 600 animals and plants.

Fellows says FWS has been laboring to address the backlog, which includes work that had to be redone when Julie MacDonald, the agency's deputy assistant secretary resigned in 2007 after an investigation found she illegally removed species and habitats from the endangered list.

Mass petitions such as those WildEarth have submitted "take an incredible amount of time to go through," Fellows says. "That can bring work on other species to a halt."

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Small snail, big issue » After FWS turned away WildEarth's petitions for protection of the Brian Head mountainsnail, the group sued Interior Secretary Ken Salazar on Jan. 7.

Threats against the snail, found only on southwestern Utah's Brian Head mountain, include ski resort expansion, hiking, mountain biking and livestock grazing, court papers say.

Shells of dead mountainsnails in a small area there were first documented in 1935. It wasn't until 1998 that scientists found 18 of them alive under current and gooseberry bushes and determined there might be 1,000 in a habitat covering less than 6 acres.

"Scientists flagged [the snail] as imperiled," Rosmarino says. That's enough for a full review under the Endangered Species Act.

Wilson remains unconvinced that WildEarth Guardians has enough evidence for its listing. That said, state biologists don't understand how the mountainsnail fits into the big picture.

"But every [species] has value," Wilson says. "If you take it out, what is the domino effect?"

To a lay observer, or to parties with vested interests, the mountainsnail may seem too insignificant to halt resort expansion, recreation or livestock operations. But wildlife advocates and the Endangered Species Act itself, Rosmarino says, make no such distinctions.

"All native imperiled species deserve a chance. That's the wisdom of the Endangered Species Act," Rosmarino says. As humans, "we are not in the position to play God when it comes to other species."

The big picture is what scientists call the Sixth Extinction. The first five were due to natural causes; the sixth is the first credited entirely to human activity.

"The extinction crisis is oftentimes about species that slip through the cracks," Rosmarino says. "They disappear without us even knowing they're there."