Black-necked Gartersnake
Thamnophis cyrtopsis

The Black-headed Gartersnake is found primarily in southeastern and central Arizona, extending into southeastern Utah, southeastern Colorado, central Texas, and west-central Guatemala. It inhabits a variety of biotic communities, including the Arizona Upland Sonoran Desertscrub, Interior Chaparral, Great Basin Conifer Woodland, and Madrean Evergreen Woodland. Isolated populations are present in the Ajo Mountains and other scattered locations. It ranges from sea level up to elevations of around 8,700 feet (2,700 meters). This species thrives in a range of habitats such as deserts, grasslands, chaparral-covered hillsides, oak woodlands, and pine forests. It is often associated with rocky canyons, semi-permanent streams, and irrigation canals, frequently near water sources but sometimes venturing far during wet weather. Typical habitats include Sonoran Desertscrub, Semidesert Grassland, Plains Grassland, and Montane Conifer Forests. The Black-headed Gartersnake is primarily diurnal and crepuscular but can also be active on warm nights. It is commonly observed in the mid-morning or late afternoon while foraging. During colder months, it hibernates. This species prefers moist or mild weather and is often found near water, although it may wander from these areas occasionally. This gartersnake's diet predominantly consists of amphibians such as tadpoles, frogs, and toads. It also consumes a variety of other prey including fish, salamanders, lizards, earthworms, and crustaceans. The Black-headed Gartersnake is viviparous, giving birth to live young. Mating likely occurs in the spring, with females typically producing 6 to 25 offspring from late June to early August. The young are born fully developed and ready to fend for themselves.