Page 13 - Black Range Naturalist, April 2020

The northern Chihuahuan Desert is marginal habitat for Hispid Cotton Rats. Cotton rats need moderate to dense grass cover for nest building and rearing young. Reduced grasslands with increased shrub cover and dependence of grasses on adequate summer rainfall have combined to make cotton rats a rarity in most of the Chihuahuan
Desert. Cotton rat nests are constructed of grass which is formed into a cup or hollow ball where the females give birth and suckle the young. Weather conditions that produce good grass growth seem to be necessary for populations of Hispid Cotton Rats. Cotton rats are known for explosive increases in population numbers and equally rapid decreases in numbers. Studies in the northern Chihuahuan Desert report increases from no Hispid Cotton Rats in dry years to more than twenty rats per acre during a wet year. The explosive nature of cotton rat populations is related to their reproductive characteristics. Litter sizes vary between one and fifteen young depending upon the quality and quantity of food. Males are sexually mature in sixty days and females are receptive thirty to forty days after birth. Females mate within one day of giving birth. Adult Hispid Cotton Rat’s diet consists mostly of stems, foliage, and seeds, but insects and other small animals are occasional parts of the diet. Water is obtained from green vegetation.
The Southern Grasshopper Mouse is the only predatory rodent that lives in the desert. These mice obtain their water from their prey. Grasshopper mice are efficient predators not only on grasshoppers and crickets but also take scorpions, centipedes, beetles, snakes, and other mice. Southern Grasshopper Mice have the intriguing behavior of “howling” to defend their territory. That behavior has been caught on film along with the successful hunts of scorpions and centipedes and is favorite footage
on TV and computer outlets. Southern Grasshopper Mice are found in most habitats in the northern Chihuahuan Desert. Grasshopper mice will also take “stink beetles” that stand on their head when threatened and exude a drop of liquid containing quinines plus other nasty
chemicals. Grasshopper mice grasp the beetle with forelimbs and push the beetles’ rear-end into the ground and proceed to eat the beetle like a sno-cone.
Above: Chihuahuan Pocket Mouse - Chaetodipus eremicus Below Right: Rock Pocket-Mouse - Chaetopidus intermedius Below Left: Hispid Cotton Rat - Sigmodon hispidus
All from Broad Canyon Ranch, North of Las Cruces, New Mexico
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