The Texas kangaroo rat is a nocturnal rodent with long hind feet, long tail and external cheek pouches. First discovered in 1894 in Clay County, Texas, Texas kangaroo rats are granivores that use their long hind feet for saltatorial, or jumping, locomotion and escaping potential predators. Historically, the species has been detected in 11 Texas counties includingArcher, Baylor, Childress, Clay, Cottle, Foard, Hardeman, Montague, Motley, Wichita and Wilbarger; and two counties in Oklahoma, Comanche and Cotton.
Habitat that supports the species' life history generally includes an accumulation of loose, friable soil, usually associated with a minor topographic uplift such as prairie mounds, or physical support. Such support includes woody vegetation like roots of shrubs and cacti, and other natural features - rocks, upturned rootballs - or manmade structures. A common characteristic of Texas kangaroo rat habitat is the presence of bare ground and short grasses, often expressed as a lack of dense vegetation. The Texas kangaroo rat digs a subterranean burrow system within loam, and or, clay-loam soils with multiple chambers branching from the main tunnel, which are used for shelter, reproduction and food storage. Resource needs for individual Texas kangaroo rats generally include:
- Friable, loam, and or, clay-loam soil for burrowing
- Predominately grasses and forbs for a food source
- Shortgrass prairie with bare ground and limited woody cover
- Topographic relief not prone to flooding events
The primary factor influencing the viability of the Texas kangaroo rat is believed to be habitat loss and degradation, largely related to historical land use change. The species' preferred habitat, short grasses interspersed with areas of bare ground and minimal woody cover, is associated with disturbance. The ecological processes within the geographic range of the Texas kangaroo rat were historically influenced by the presence of American bison, black-tailed prairie dog and periodic wildfire, creating a mosaic of disturbed patches on the landscape that provided suitable habitat for the species. The expansion of Euro-Americans into the West beginning in the 1800s led directly to the decline of bison and black-tailed prairie dogs. Domestic cattle can replace some lost historical ecosystem functions in a limited capacity, but the loss of the natural assemblage provide by bison, prairie dogs and fire appears to have negatively impacted the availability of habitat for the Texas kangaroo rat.
The conversion of native rangeland to row crops is a direct loss of habitat because TKR typically do not construct burrows in agricultural crops. The ground disturbance caused by plowing and disking associated with farming, which disturbs the soil substrate, results in a loss of habitat in areas that could have previously supported the species.
The early 20th century saw a steady increase in human population within the Texas kangaroo rat's range, fueled by westward expansion and an oil boom. As a result, associated man-made infrastructure such as buildings and roads were developed in greater numbers. While paved roads may fragment habitat and create a barrier to Texas kangaroo rat dispersal, unpaved road edge provides non-traditional habitat where the species is often found. The extent to which road edge habitat provides all resource needs for the species is unknown, but the vast majority of observations from the most recent rangewide surveys were made along unpaved roadside habitat due to limited access to private lands.
Woody plant encroachment threatens the persistence of grassland and savanna ecosystems and their endemic biodiversity, and represents a loss of suitable habitat for Texas kangaroo rats, as the species avoids areas of dense vegetation and closed canopy cover. Evidence suggests that within northwest Texas, the effect ofand fire suppression would result in a shrubland-dominated landscape, thus decreasing the amount of available Texas kangaroo rat habitat.
Little research exists on the reproduction and brood rearing of Texas kangaroo rats. Most of the information published is data recorded secondarily to primary study objectives. The species appears capable of breeding throughout the calendar year, with peak times in February and August. Females give birth early in the calendar year, and young-of-year are able to birth their first litter in the late summer or early fall of the same year, as noted by Packard; and Carter et al. Average litter size is two to three pups, according to Martin. Sub-adults molt in the fall, while adults molt annually at any time throughout the year. This suggests a prolonged reproductive cycle and that more than a single reproductive cycle occurs annually, according to Webster and Jones; and Martin. Lifespan of the Texas kangaroo rat in the wild is approximately 2 years, according to Martin. Individual males and females of the species require suitable breeding habitat to establish a territory, construct a burrow in an appropriate soil substrate, and forage for themselves and their offspring. Territories encompass an average of 0.20 acre (0.08 hectare), according to Roberts and Packard. Bare ground is important as males and females display sexual receptivity by dust-bathing at bare ground sites within their territory and leaving their “scent,” an oily substance exuded by dorsal sebaceous glands, as noted by Genoways and Brown; Stangl et al.; and Goetze et al.
Texas kangaroo rats have a lifespan of approximately 2 years in the wild; however individuals in captivity live well beyond 2 years, as noted by Martin; and D. Barber.
The Texas kangaroo rat is an opportunistic seed gatherer, according to Martin. Cheek pouch contents of Texas kangaroo rats sampled in Hardeman County contained 69.5% grass seeds, including cultivated oats (Avena sativa and Sorghum halepense); fruits and flowers of forbs were also common at 42.3%, according to Chapman. Mesquite seeds were found in the cheek pouches of only one individual, Chapman notes. Texas kangaroo rats forage for seeds from 8 to 65 feet (2.5 to 20 meters) from burrow entrances, according to Goetze et al.; Otto notes though that they have been observed searching 164 feet (50 meters) from burrows. Food items are not consumed immediately; instead they are placed in cheek pouches and later cached near burrow entrances or within chambers of their tunnel, as noted by Goetze et al. Texas kangaroo rats are not known to hibernate but use food caches in burrows that serve as reserves when above-ground food is unavailable during winter or inclement weather, as noted by Dalquest and Collier; Lewis; and Chapman. Green vegetation, such as stems and leaves, gathered along with seeds, may be a source of moisture, noted Chapman. Texas kangaroo rats do not use planted wheat fields as a food source, according to Goetze et al. Recent radio-telemetry research shows the species using dirt road shoulders within their home range and intermittent activity in adjacent crop fields, according to Veech et al., presumably foraging for seeds collecting on the ground.
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