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Mexican Gartersnake (Thamnophis eques)

[/vc_column_text][gap size=”12px” id=”” class=”” style=””][/vc_column][/vc_row][vc_row][vc_column width=”1/2″][vc_single_image image=”179″ img_size=”large” alignment=”center” style=”vc_box_rounded”][vc_column_text]Mexican Gartersnake, Rancho Los Fresnos, Sonora, MX. Photo by Jim Rorabaugh[/vc_column_text][/vc_column][vc_column width=”1/2″][vc_row_inner][vc_column_inner width=”1/2″][vc_single_image image=”2635″ img_size=”medium” alignment=”center” onclick=”img_link_large”][vc_column_text]Mexican Gartersnake showing the anterior lateral light stripe on the 3rd and 4th scale rows. Photo by Jim Rorabaugh[/vc_column_text][gap size=”12px” id=”” class=”” style=””][/vc_column_inner][vc_column_inner width=”1/2″][vc_single_image image=”2636″ img_size=”medium” alignment=”center” style=”vc_box_rounded” onclick=”img_link_large”][vc_column_text]Mexican Gartersnake, Temosachic, Chihuahua, MX. Photo by Jim Rorabaugh[/vc_column_text][gap size=”12px” id=”” class=”” style=””][/vc_column_inner][/vc_row_inner][vc_row_inner][vc_column_inner width=”1/2″][vc_single_image image=”2637″ img_size=”medium” alignment=”center” style=”vc_box_rounded” onclick=”img_link_large”][vc_column_text]Mexican Gartersnake, Rancho Los Fresnos, Sonora, MX, Photo by Jim Rorabaugh[/vc_column_text][gap size=”12px” id=”” class=”” style=””][/vc_column_inner][vc_column_inner width=”1/2″][vc_single_image image=”2639″ img_size=”medium” alignment=”center” style=”vc_box_rounded” onclick=”img_link_large”][vc_column_text]Mexican Gartersnake, in situ on the Santa Cruz River, Arizona. Photo by Jim Rorabaugh[/vc_column_text][gap size=”12px” id=”” class=”” style=””][/vc_column_inner][/vc_row_inner][/vc_column][/vc_row][vc_row][vc_column width=”1/6″][/vc_column][vc_column width=”2/3″][vc_column_text]

Description

Editor’s Note: On 8 July 2014, the Northern Mexican Gartersnake (Thamnophis eques megalops) was listed as a threatened species under the U.S. Endangered Species Act.  The final rule listing this snake, which also listed the Narrow-headed Gartersnake, T. rufipunctatus, as threatened, contains an excellent review of the natural history, distribution, threats, and conservation status of both species.  It can be accessed here:

http://ecos.fws.gov/speciesProfile/profile/speciesProfile.action?spcode=C04Q#status

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A relatively long, stout-bodied gartersnake where females may reach a length of 112 cm. (44 in.). Mexican Gartersnakes have 3 bold stripes and are easily confused with the Black-necked and Checkered gartersnakes that are found throughout their range. All 3 species can be identified by noting which scale rows the lateral stripe falls across in the anterior portion of the body. Mexican Gartersnake’s lateral stripe occurs on scale rows 3 & 4, on rows 2 & 3 on Black-necked Gartersnakes and row 3 in checkered gartersnakes.

An extremely aquatic, secretive gartersnake, it is rarely found away from permanent water and dense vegetation. In Arizona, it inhabits cienegas, cienega-streams and cottonwood-willow riparian areas. Mexican Gartersnakes are distributed from southern Mexico north through the Mexican Plateau and Highlands to central Arizona and west-central New Mexico. Historically, in Arizona, they were found at low- to mid-elevations, 530-1875 m. (1720-6150 ft.), throughout the greater Gila River Basin and the headwaters of the Rio Yaqui (San Bernardino National Wildlife Refuge). Once common in the Tucson Basin, it is now extirpated from the area.

Mexican Gartersnakes primarily feed on frogs and fish although they are known to take small rodents and lizards. Females give birth to up to 25 live young between late May and early July. They are active during the warmer months of the year and are most readily observed in the morning. If handled or threatened, Mexican Gartersnakes will strike repeatedly and bite, all the while smearing a strong smelling musk and feces on the handler.

Mexican Gartersnakes have declined throughout much of their range in Arizona and are considered a Species of Special Concern by the Arizona Game and Fish Department and it is illegal to handle or collect them without the proper permits. Although Mexican Gartersnakes do not have official Federal protection, much of their remaining habitats are protected, at least in part, due to the Federal listing, under the Endangered Species Act, of several other wetland obligate species including Sonoran Tiger Salamanders, Chiricahua Leopard Frogs and Huachuca Water Umbel.

Reasons for decline include alteration and destruction of their aquatic habitat and the introductions of exotic species (e.g., bullfrogs). Surveys conducted during the mid-1980’s and 2000 suggest this trend is continuing. On a positive note, a population in Santa Cruz Co., which was thought to be extirpated, was recently found to persist there, albeit in low numbers.

In Arizona the subspecies Thamnophis eques megalops, Northen Mexican Gartersnake is found.

Author: Eric Wallace
Originally published in the Sonoran Herpetologist “Herpetofauna of the 100-mile Circle” 15 (10) 2002

For additional information on this species, please see the following volumes and pages in the Sonoran Herpetologist: 2006 Feb:18; 2006 Nov:127; 2008 Jul:74-77.

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