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Saguaro Nat'l Park's citizen-powered Gila Monster Project crawls along for more than a decade

Saguaro Nat'l Park's citizen-powered Gila Monster Project crawls along for more than a decade

  • Saguaro National Park can utilize photographs to match Gila monsters spotted by the public years apart like the lizard named 'Kara' pictured above.
    National Park ServiceSaguaro National Park can utilize photographs to match Gila monsters spotted by the public years apart like the lizard named 'Kara' pictured above.

At the entrance to Broadway’s sandy trailhead into Saguaro National Park there is a flier that doesn’t quite fit in. The white sheet, which hangs among signs prohibiting pets and horses from the dirt trails, contains a picture of an orange and black Gila monster and a simple question: “Have You Seen Me In Saguaro National Park?”

Rather than just a warning against the venomous lizard, the announcement invites visitors to participate in a science project that’s been going on for many years.

The Gila Monster Project has been calling on members of the public to submit photos of the reptiles for more than 15 years. More than 1,000 images later, the initiative is still going and photographs from the public have become the bulk of the work.

The photos began as a way to complement ongoing University of Arizona research in Saguaro National Park and to get the public involved, said Kevin Bonine, who helped start the scientific endeavor in 2005.

“And we could get some information about the species that way and also incentivize folks, staff and visitors to the national park as well as residents that live nearby, incentivize them to be more curious about some of the natural history of the ecology of the region,” said Bonine, a director at Biosphere 2.

The colorful reptile is a Southern Arizona staple that’s also found in northern Mexico, and known for its orangish and black pattern of scales. The beaded lizard can be up to about 22 inches long and eats things like eggs along with small mammals and birds. The venomous animal is not aggressive, but it may bite if forced on the defensive and transfer venom through its teeth. 

While not endangered, the reptile is listed as “near threatened” by the International Union for Conservation of Nature. Gila monsters are protected in Arizona from being killed, moved or harassed.

The university’s research included taking small tissue samples from the creatures to examine their DNA, Bonine said. Soon after the small-scale research launched officials began encouraging the public to submit photos of the lizards.

The reptiles were chosen because of factors like their elusive nature and the fixed patterns that mature Gila monsters have, which return even after they shed their skin, he said. These patterns lent themselves to what Bonine called the “public science” portion of the research.

Unlike the more involved work of studying the lizard's genetics, which UA students assisted with, members of the public could submit photos to help identify the creatures by their unique scale patterns, which are often compared to fingerprints.

“It's not like rings and walls, kind of like we have on our fingerprints,” Bonine said. “It’s sort of the spacing and the patterning of the black pigmentation versus the sort of salmon or pink or coral color that comprises the other part of their pattern.”

Don Swann, a Saguaro National Park biologist, has been involved with the Gila monster work since the start and helps continue it today. Roughly six or seven years ago the university’s involvement with the project decreased and the park’s role increased with that of the public, Swann said. This led to placing fliers on trailheads and further encouraging the public’s help. 

Once received, the images are organized by date and location and analyzed to see if the individual in the photograph matches one already in the system. If someone submits multiple photos of the reptile from different angles the photos are merged in Photoshop, he said. The image is then run through a system that compares it to others taken nearby. This process is currently done manually, with the help of a single volunteer who comes in once or twice a week.

The original UA-led research discovered that the park had a genetically diverse and healthy population of the lizards. The continued work is looking to find out information like how long Gila monsters live in the wild, how much they move around and when the lizards are active.

“By taking the long view and using these photographs that are provided to us by visitors we can start to get some insights into an animal that really is still kind of a mystery to not only most of us but to most biologists,” Swann said.

While it’ll be several years before findings are published, the data indicates Gila monsters are very active in April and May and appear at night during the monsoon season, he said. Based on the present data, Swann predicts that the reptiles are“homebodies” that tend to stay in a relatively small area. Some individuals pictured in the area have proven that the lizards can live to at least 12 years old outside of captivity.

Officials have also found that a small percentage of the lizards have part of their tail missing, which does not grow back. The culprit is unknown, Swann said, but one hypothesis is that ground squirrels may be responsible for the damage done to the extremity.

“We're finding evidence that the tails are kind of missing at the end, which we suspect might be some kind of predator,” he said. “We don't know, we haven't seen that, but we'll see that the tail’s kind of missing at the end or the bone is exposed where it broke off.”

About 660 individuals have been identified since 2001, Swann said, and more than 150 additional photos are either blurry or partials that cannot be matched to existing images. The majority of the sightings have occurred in Saguaro East compared with the park’s western district, which is drier and at a lower elevation, Bonine said.

The public is encouraged to continue submitting photographs of the lizard, but officials ask that the images be from inside or very close to Saguaro National Park. Photos can be submitted to

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