Known as the Crawford’s gray shrew, the Notiosorex crawfordi is also referred to as the desert shrew. It is found in northern Mexico and the southwestern United States. It is the only shrew known to live in the Mojave Desert. There have been numerous sightings of the creature in the Big Morongo Canyon Preserve.
It is a member of the order Soricomorpha and the family Soricidae. Crawford’s gray shrew is among the smallest of desert mammals and one of the world’s smallest homeotherms. Fully grown this shrew extends to little more than two inches long, half of which is the tail. They weigh in at no more than 5 to six grams, or .18 to .22 ounces.
The shrews are gray brown on top and most light gray below. It sports small but prominent, ears.
Crawford’s shrews are generally born in litters of three to six during the summer. Infants are the size of a honeybee, hairless and pink in color. They grow rapidly, reaching full size in about a month. Mothers nurse their young and then provide them with regurgitus as they mature.
By the fall, the shrews leave the nest and begins to forage on lizards, small mice, scorpions and arthropods. Shrews have accelerated metabolisms and can easily eat as much as or more than three-quarters of their body weight in food per day.
Because of their metabolisms, shrews are prone to overheating. This is doubly problematic for desert shrews as they normally do not have access to a ready water supply. A strategy they use to conserve water consists of finding shelters from the heat. Rather than construct their own burrows, they prepare themselves small nests in pack rat houses or in cavities under dead agaves.
Desert shrews further conserve water by being nocturnal, unlike other shrews, which hunt day and night to avoid starvation. Because of its poor vision, the Crawford’s gray shrew uses its finely attuned hearing and acute sense of smell to hunt. They are also make a practice of echolocation, similar to bats, using the resonance from their high-pitched squeaks to locate prey.
Shrews make a gruesome habit of not killing their prey, but rendering them immobile by biting off their legs or partially crushing their heads so they can keep their victims hydrated and a source of liquids.
Another method the shrew uses to reduce water loss is to warm air to its body temperature before inhaling to thereby absorb the resultant water vapor through its nasal membranes. When the exhaled air cools within its long snout, this creates condensation which the shrew also absorbs.
Despite its high active time metabolism, the desert shrew has the lowest resting metabolic rate of all shrew species.
Because of its voracious eating habits, Crawford’s gray shrews expel copious amounts of nitrogenous waste. They reduce water loss from urinating by concentrating urea in the urine. The urine of a Crawford’s shrew is four times more concentrated than that of a human.
Despite all of these adaptions, the desert shrew is victim of its own highly charged metabolism and is relatively short lived, dying off before it reaches the age of two. Moreover it is itself prey to nocturnal hunters, such as snakes and owls, although it does have a partial defense in this regard in that it emits a musky odor that makes it less appetizing to mammalian predators.