Despite the recent discovery of the endangered Mexican garter snake near Lake Havasu City, there is no clear evidence on just how many of the reptiles live along the Colorado River.
“We don’t know much about them in Lake Havasu,” said Thomas R. Jones, amphibians and reptiles program manager for Arizona Game and Fish.
“The Mexican garter snake, we assume, used to be common up and down the Colorado River, and the only museum records of the snake are from 1904 and 1911, then nothing until 2015 when one animal was photographed in Havasu National Wildlife Refuge.”
The Lake Havasu snake was a welcome surprise, Jones added, because Game and Fish thought they had vanished from the Colorado River.
“We have no idea on what their status is there,” Jone said. “We haven’t come to Havasu to try to trap them and find out more. The only reason we haven’t is because of the lack of resources. I don’t have the staff that I can send up there.”
The elusive nature of the snake also contributes to making an accurate count problematic.
“In most places on the Colorado River where there is backwater and sloughs the vegetation is so thick we are unlikely to see them even if they are there,” he said. “They are stealthy. They are secretive, and to be honest folks not know what they are when they see them.”
Even the experts often times are confused.
“There was a recent discovery of Mexican garter snakes in the upper reaches of the Bill Williams watershed,” Jones said. “There was a photograph taken by a Bureau of Land Management biologist in 2010. They just assumed it was a different species, so they shelved that photograph.”
Nobody knew the specie identification until it made its way to Jones for a positive ID.
“This is a snake that’s had a bit of a checkered history with the Endangered Species Act. They were petitioned for listing in 2006, and the U.S. Fish and Wildlife Service determined that listing was not warranted,” Jones said.
“That decision was controversial and was challenged because the then FWS Deputy Assistant Secretary Julie McDonald had intervened in some way and influenced the final decision.”
FWS reinitiated a status review and published another 12-month finding in November 2008 that concluded that listing was warranted, but precluded by other higher priority actions. The Mexican garter snake were brought back up again and listed in 2014.
“When they were being considered for listing, we already knew their number had declined in most areas and the department started work on gathering information in earnest,” Jones said.
Working began to gather basic biological information about the snake in 2007 at Bubbling Ponds and Page Springs fish hatcheries, where they appeared to be doing well.
Recent efforts have been focused on raising the snakes in captivity and releasing them into the wild, removal of exotic species particular bull frogs that prey on Mexican garter snakes and reintroducing the ESA listed Chiricahua leopard frog, which is a favorite snack of the snake.
“Still, I think the species is declining in many areas,” Jones said. “It suffers from a lot of threats primary among them is habitat loss, invasive species and loss of their native prey base, so they face a lot of problems.”
Although the Lake Havasu population is unknown the Mexican snake is found in the tributaries of the Bill Williams watershed along the Big Sandy and Santa Maria rivers, as well as below the Alamo Dam.
“These were all recent discoveries, happy accidents,” Jones said. “On the one hand in many parts of southeastern and central Arizona they’re still fighting a lot of threats. In the western part of the state they seem to be doing well, so I guess you can say it’s a mixed bag.”
Mexican Garter snake
The northern Mexican gartersnake can reach a maximum length of 44 inches. It ranges in background color from olive to olive-brown to olive-gray. Three stripes run the length of the body with a yellow stripe down the back that darkens toward the tail.
Bill Williams River
Discovered in 2012
Big Sandy River
Discovered in 2010; went unnoticed until 2014.
Santa Maria River
Confirmed in 2015
Agua Fria River
2016 surveys failed to confirm historical presence. Game and Fish believe the snake might be extirpated from this river system. Invasive species – crayfish and bullfrogs – have caused declines, along with loss of native fish and frog prey base.