Sonoran Lyresnake – Tucson Herpetological Society

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Sonoran Lyresnake (Trimorphodon lambda)

[/vc_column_text][gap size=”12px” id=”” class=”” style=””][/vc_column][/vc_row][vc_row][vc_column width=”1/2″][vc_single_image image=”2119″ img_size=”large” alignment=”center” style=”vc_box_rounded”][vc_column_text]Sonoran Lyresnake, Rancho El Aribabi, Sonora. 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=”2448″ img_size=”medium” alignment=”center” onclick=”img_link_large”][vc_column_text]Juvenile Sonoran Lyresnake, Rancho El Aribabi, 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=”2449″ img_size=”medium” alignment=”center” style=”vc_box_rounded” onclick=”img_link_large”][vc_column_text]Sonoran Lyresnake in a crevice, Sierra Aconchi, Sonora, 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=”2450″ img_size=”medium” alignment=”center” style=”vc_box_rounded” onclick=”img_link_large”][vc_column_text]Large Scolopendra centipede with juvenile Lyresnake, Little Ajo Mtns. Predator or scavenger? Photo by Tim Tibbitts[/vc_column_text][gap size=”12px” id=”” class=”” style=””][/vc_column_inner][vc_column_inner width=”1/2″][vc_single_image image=”2453″ img_size=”medium” alignment=”center” style=”vc_box_rounded” onclick=”img_link_large”][vc_column_text]Sonoran Lyresnake. Photo by Young Cage[/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=”2452″ img_size=”medium” alignment=”center” style=”vc_box_rounded” onclick=”img_link_large”][vc_column_text]Sonoran Lyresnake. Photo by Young Cage[/vc_column_text][/vc_column_inner][vc_column_inner width=”1/2″][vc_single_image image=”2451″ img_size=”medium” alignment=”center” style=”vc_box_rounded” onclick=”img_link_large”][vc_column_text]Sonoran Lyresnake, Sierra Aconchi, Sonora. Photo by Jim Rorabaugh[/vc_column_text][/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

The Sonoran Lyresnake (Trimorphodon lambda) is a slender snake of moderate length with a head that is broader than the neck, large, protuberant eyes with vertically elliptical pupils, a mean of 22 (range 19-25) smooth dorsal scale rows at mid-body, and a divided anal plate and subcaudals. Maximum total length is 1049 mm, but most are less than 900 mm. Atop the head is a dark “V” or lyre marking with the bottom of the “V” between the eyes (may be indistinct in some southeastern Arizona specimens). A dark bar is present across the snout just anterior to the eyes. Dorsally it is gray to light brown with light bordered, light centered, dark brown saddles on the body and tail. The dark saddles on the body are 3-9 (mean = 5) scales long along the mid-dorsal line at mid-body, and the seventh and eighth saddles (counting from behind the head) are separated by four scales on average. Much smaller lateral dark spots or blotches may be present near the boundary between the dorsal and ventral scales. The venter is white to gray with a row of dark spots along each side that are a continuation of the lateral blotches. Ventral scales number 211–240 in males and 223–249 in females. Males also tend to average fewer dorsal saddles than females, have proportionally longer tails, and a shorter maximum length. Juveniles are more boldly marked and the light centers in the dorsal saddles may be indistinct or absent. Toxins produced in a Duvernoy’s gland are delivered to prey and attackers via elongated, grooved teeth in the rear of the upper jaw. A large individual is capable of delivering a venomous bite to a person. Symptoms range from none to local redness, itching, swelling, and numbness, particularly if the snake is allowed to chew (Ernst and Ernst 2003, Devitt et al. 2008).

Until recently, the Sonoran Lyresnake was considered one of six subspecies of the broad-ranging Western Lyresnake (Trimorphodon biscutatus). LaDuc and Johnson (2003) elevated the northeastern, primarily Chihuahuan Desert, T. b. vilkinsonii (Chihuahuan Lyresnake) to species. Devitt et al. (2008) elevated the remaining five subspecies, including T. b. lambda, to species and further confirmed the work of LaDuc and Johnson (2003). No subspecies of the Sonoran Lyresnake are recognized (Crother 2012).

The large eyes with vertically elliptical pupils, the distinctive light-centered dorsal saddles, and the lyre or “V” marking atop the head make this snake easily recognizable in the 100-Mile Circle. In the Peloncillo Mountains and possibly elsewhere in extreme southeastern Arizona are lyresnakes that lack or have indistinct lyre or “V” markings atop the head, and share other characters with the Chihuahuan Lyresnake. These snakes are thought to be the result of hybridization. However, no true Chihuahuan Lyresnakes are known from Arizona (Devitt et al. 2008).

This species is most commonly found in the rocky terrain of montane canyons and slopes, but it occurs sparingly onto bajadas and into valleys, as well, even where rocks are scarce (Lowe et al. 1986, Stebbins and McGinnis 2012). Elevational range is about 425-2240 m in the Circle. The latter, high elevation record comes from the Mount Lemmon Highway in the Santa Catalina Mountains. In the 100-Mile Circle, the Sonoran Lyresnake occurs in a variety of vegetation communities, including Sonoran and Chihuahuan desertscrub, inland chaparral, semi-desert grassland, oak woodland, and pine-oak woodland. In the Circle, it also likely occurs in foothills thornscub and may occur in mixed conifer forest.

The Sonoran Lyresnake is of widespread occurrence in the 100-Mile Circle, likely occupying all mountain ranges and associated rocky bajadas. It is probably only absent from mountain tops (>2240 m), some valley bottoms, and developed areas, such as cities and agricultural areas. The species is found from southern Nevada and extreme southwestern Utah south through southeastern California east of the Salton Sea, much of Arizona except for the northeastern quarter, southwestern New Mexico, as well as most of Sonora and northern Sinaloa.

This is primarily a nocturnal snake, although it can be found inside rock crevices and under rocks during the day. It is rarely encountered surface active in the late afternoon or early morning. It has been collected every month of the year in the Circle, although most are found from April through October. Repp (1998) reported on a Sonoran Lyresnake found hibernating deep in a south-facing rock crevice. This snake is usually found on the ground or amidst rocks, but it climbs well over rock faces and into trees and shrubs.

Lowe et al. (1986) reported that eggs are laid in the late spring to early summer, which hatch in September and October. In Sonoran Lyresnakes from Arizona, Goldberg (1995) found males actively forming sperm in spring, summer, and fall. The smallest reproductively active male was 448 mm SVL. Females with eight and ten enlarged follicles were noted, both collected in May. The smallest reproductively active female was 718 mm SVL. For the Trimorphodon biscutatus complex of species, clutch size is 6-20 (Ernst and Ernst 2003). Hatchlings are about 205-264 mm total length.

Lowe et al. (1986) reported that rock and plant dwelling lizards and mice make up the bulk of the diet. Bats and perhaps birds and other snakes may also be taken (Degenhardt et al. 1996, Stebbins and McGinnis 2012). Specimens in the University of Arizona collection have been found to have a Tiger Whiptail (Aspidoscelis tigris) and Clark’s Spiny Lizard (Sceloporus clarkii) in their stomachs. Captives were fed Pocket Mice (Perognathus), Deer Mice (Permomyscus), House Mice (Mus musculus), Ornate Tree Lizards (Urosaurus ornatus), Common Side-blotched Lizards (Uta stansburiana), and Western Banded Geckos (Coleonyx variegatus, Jones 1988). Jones (1981, 1988) noted that lizards were grasped by the head and held for several minutes until immobilized. Rodents were, however, constricted for 3-5 minutes with two to four tight coils. Ernst and Ernst (2003) questioned whether mice are actually constricted or just held in place. Trimorphodon venom is less effective on mice than lizards, and is probably hemorrhagic instead of neurotoxic (Cowles and Bogert 1935, Jones 1981, Ernst and Ernst 2003). Venom is chewed into the wound (Cowles and Bogert 1935).

When threatened, the Sonoran Lyresnake will often rattle its tail. It will sometimes raise the anterior portion of the body, and strike and bite if further provoked. Tim Tibbitts observed a dead juvenile Sonoran Lyresnake in the grasp of a large Scolopendra heros centipede in the Little Ajo Mountains, Pima County (see image gallery), but whether the snake was predated or scavenged is unknown.

The conservation status of the Sonoran Lyresnake has not yet been evaluated by the IUCN. With a valid Arizona hunting license, four can be collected per year or held in possession, alive or dead, except that collection is prohibited in protected areas, such as National Park Service units without special authorization. This species is eliminated from areas of heavy urbanization and agriculture, but those activities take place largely outside of its typical rocky habitats. There is no reason to believe it has declined in wildland areas.

Sonoran Lyresnake (Trimorphodon lambda)

Description

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