Scientists thought this snake vanished 100 years ago. Then they found one

The Republic | azcentral.com

The northern Mexican gartersnake was rediscovered along the Colorado River in 2015, 111 years since it had last been seen.

The year was 2015 and, as biologist Michael Lester recalls, he was walking a familiar trail near the Colorado River looking for birds when he saw a long object on the ground and thought, "There wasn’t a stick there before."

He was right — and it wasn't a stick.

It was a northern Mexican garter snake, which was designated as a threatened species the year before and hadn't been seen along the Colorado River for the past 111 years.

Lester was working as a seasonal technician for a bird research group at Beal Lake on the Havasu National Wildlife Refuge.

"When I got back to our shared housing, I mentioned to my field crew leader, 'Oh yeah, I saw a garter snake today,' pretty nonchalantly," he recalled in an interview. "She had this look on her face, and she was like, 'What are you talking about? There are no garter snakes in this area.' "

Lester showed her a photo he took of it, and they sent it to the Arizona Game and Fish Department and U.S. Fish and Wildlife Service for verification.

They verified it, he recalled, and they knew they had made an unlikely discovery.

A program that conserves, restores

Water levels in Lake Mead, behind Hoover Dam, fell sharply during an extended drought on the Colorado River.

The Colorado River, heavily dammed and in demand, is far from the river it once was.

Its water runs through seven states and Mexico and serves more than 25 million people.

The acts of delivering water and generating power have worn on the watercourse and its accompanying habitats.

Some endangered and threatened species call the river home, and in 2005, the Lower Colorado River Multi-Species Conservation Program was officially launched to protect those species.

Although the U.S. Bureau of Reclamation is the program's implementing agency, the program itself is made up of more than 50 governmental and non-governmental agencies that use the river's water.

The involved organizations are tasked with ensuring endangered species are cared for along the river, and officials try to preemptively care for species they think may end up on the endangered species list in the near future.

MSCP Manager John Swett, who works for the Bureau of Reclamation, said the program has been mostly effective at predicting which species it needs to care for before they become listed.

"Our crystal ball has been pretty good, but it’s not 100 percent. It wasn’t supposed to be here," he said of the garter snake. "... There hadn’t been one in 100 years."

Jeff Servoss is the herpetologist lead for the U.S. Fish and Wildlife Service's northern Mexican gartersnake recovery program. (Scientists prefer the one-word spelling.)

While the restoration work being done through the conservation program benefits the river and the species that live there, he said he doesn't believe it's directly responsible for the snake's apparent re-appearance.

"I think the case more likely is that it’s always been there in exceptionally low density."

The aquatic snakes have historically appeared in "virtually every single major watershed in Arizona," except the Colorado River's tributary, the Little Colorado River, he said.

Since the 2015 rediscovery, the garter snakes have popped up near Bill Williams River frequently, Servoss said. He attributes that, at least in part, to populations of lowland leopard frogs, a critical prey for the snakes.

"As long as you can promote a leopard frog and keep them as part of your community, there’s a chance you could have success with Mexican gartersnakes as well," he said.

Protecting an animal no one had seen

The organizations involved with the MSCP restore and build habitats along the river, ensuring everything they do complies with the Endangered Species Act. Officials try to act proactively.

In 2014, when the northern Mexican garter snake was listed as threatened, officials weren't sure they would ever come across one of the snakes.

Jessica Gwinn, Colorado River coordinator for the U.S. Fish and Wildlife Service, said it was encouraging to see the progress the Multi-Species Conservation Program had made in its first 10 years.

Although the snake's threatened listing caused officials to take it into account, they all thought it was already gone, she said.

The U.S. Fish and Wildlife Service and the Bureau of Reclamation hope to add the snake to the list of species covered under the program, according to a Fish and Wildlife release.

Lester's findings were published in a brief Herpetological Review entry but were otherwise met with scant public notice.

"Considered extirpated from the Colorado River, this is the first sighting ... along the main stem of the Colorado River in over a century," he wrote. "Nearest known specimen is from Clark (County), Nevada."

Although officials have speculated — maybe the snake lived on the refuge for years in such low density that it went undetected, or maybe the restoration project lured the snake back — there isn't a simple answer for why the snake was spotted or how it got there.

Other rediscoveries

Santa Cruz River water quality has improved but is still a matter of concern.

The snake's case isn't entirely uncommon.

Officials in December announced the endangered Gila topminnow was rediscovered in the Santa Cruz River in northwest Tucson after an absence of more than 70 years.

The species is native to Arizona and could signal an improvement in the river's health, according to the Fish and Wildlife Service news release.

Few fish of any kind were found in the river for decades, the release said, because the waters were too polluted. Officials believe improvements made to nearby facilities in Tucson and Nogales, Arizona, that release water into the river could be responsible for more fish appearing.

"Finding Gila topminnow in the net was unexpected,” Ross Timmons, native fish biologist with the Arizona Game and Fish Department, said in a statement. “After this previous summer’s runoff, we were expecting to find a different native fish, the longfin dace, but instead we found Gila topminnow."

Although there have been improvements to the quality of water entering the river, there are still concerns.

The International Outfall Interceptor pipeline brings raw sewage to a wastewater treatment plant in Nogales. In July, it had a pipe failure and dumped untreated sewage directly into the river, according to the Fish and Wildlife release.

The International Outfall Interceptor takes water from Nogales, Arizona, and Nogales, Sonora, to the Nogales International Wastewater Treatment Plant in Arizona, according to Santa Cruz County documents. The treated water is then dumped into the Santa Cruz River to recharge groundwater levels.

The plant is managed by the U.S. International Boundary and Water Commission.

Officials say the incident put "at risk decades of progress made in restoring the river's health and the region's economy and drinking water."

The Gila topminnow were rediscovered by an annual fish survey conducted by the Sonoran Institute, the Fish and Wildlife Service, the Arizona Game and Fish Department and others.

Snake has significance for river, Valley

The rediscovery of a small snake could have positive impacts for Valley residents.

Jeff Humphrey, a spokesman for the U.S. Fish and Wildlife in Phoenix, said it shows that river restoration is working and water will continue to flow from the river into the Valley.

The snake's rediscovery shows both the Colorado River and its supply are healthy, in spite of the changes it's undergone, Humphrey said.

"When the water providers have the assurances that water delivery can continue to occur, unbeknownst to all of us in Phoenix, it provides greater assurances that we have long-term water supply here," he said.

And regardless of whether the Multi-Species Conservation Program is responsible for the snake's rediscovery, biologists see the new and improved habitats as the river being used to its full potential.

The river has changed over decades of use by dozens of agencies, millions of families. But with restoration, officials see a healthy river that can thrive. Families can visit it, water can course through it and wildlife can live in it.

"Even though it wasn’t a target species ... everyone was really excited," said Gwinn of the Fish and Wildlife Service. "Like, wow, this is working."

Environmental coverage on azcentral.com and in The Arizona Republic is supported by a grant from the Nina Mason Pulliam Charitable Trust. Follow The Republic environmental reporting team at OurGrandAZ on Facebook, Twitter and Instagram.

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