Sigmodon hispidus eremicus

Yuma Hispid Cotton Rat

Family: Cricetidae · Class: Mammalia · Order: Rodentia

Conservation status: G5T2T3 S2

The Yuma hispid cotton rat (Sigmodon hispidus eremicus) is a medium-sized rodent subspecies endemic to the Colorado River valley region of southwestern United States and northwestern Mexico. Adults typically measure 200-300 mm (7.9-11.8 inches) in total length, including a scaly tail of 80-130 mm (3.1-5.1 inches). The body weight ranges from 100-200 grams (3.5-7.1 ounces). The dorsal pelage is grayish-brown to dark brown with coarse, hispid (bristly) guard hairs that give the subspecies its common name. The ventral surface is lighter, ranging from grayish-white to buff. The ears are relatively small and rounded, and the feet are adapted for terrestrial locomotion with well-developed claws. Historically, the Yuma hispid cotton rat occurred along the lower Colorado River from southern Nevada through Arizona and California into Sonora and Baja California, Mexico. The subspecies' range has contracted significantly from historical levels. In California, populations were documented in Imperial County along the Colorado River floodplain, but current distribution is highly fragmented and restricted to remnant habitat patches. The subspecies also occurs in southwestern Arizona and northwestern Mexico (USFWS 1994). Yuma hispid cotton rats inhabit dense riparian vegetation along the Colorado River and its tributaries, typically in areas below 150 meters (490 feet) elevation. They require thick understory cover, particularly dense stands of arrowweed (Pluchea sericea), quailbush (Atriplex lentiformis), and mesquite (Prosopis species). The subspecies constructs runway systems through dense vegetation and builds globular nests of woven plant material above ground level. They prefer areas with permanent water sources and are closely associated with the natural flood cycles that historically maintained their riparian habitat. These cotton rats are primarily herbivorous, feeding on green vegetation, seeds, and occasionally bark. They consume a variety of riparian plants including saltgrass, bermuda grass, and the succulent parts of shrubs. Reproduction occurs year-round in favorable conditions, with females producing multiple litters annually. Gestation lasts approximately 27 days, and litter sizes typically range from 2-6 young. The species is largely nocturnal and crepuscular, with peak activity occurring during dawn and dusk hours. The Yuma hispid cotton rat has a Global/State Rank of G5T2T3 S2, indicating the subspecies is imperiled to vulnerable globally and imperiled in California. The primary threat is habitat loss due to water diversions, flood control measures, and agricultural conversion that have eliminated much of the natural riparian ecosystem along the Colorado River. Urban development and invasive plant species further degrade remaining habitat. Dam construction has altered the natural flooding regime essential for maintaining the dense riparian vegetation required by this subspecies. Conservation efforts focus on habitat restoration and protection of remaining riparian corridors, though recovery is complicated by ongoing water management challenges in the Colorado River system.

Data from The California Species Project — 14,000+ California species with verified data from CNPS, CDFW, USFWS, and more.