Perception Channels: tactile ; chemical
Notiosorex crawfordi live in a habitat that has become a place for human recreation. Off-road vehicles, camping, along with other activities and the refuse that individuals leave behind have an impact on the shrew. The degregation of the habitat may cause these animals to become threatened. Mexico has listed this species as threatened.
US Federal List: no special status
CITES: no special status
IUCN Red List of Threatened Species: least concern
Shrew help control some of the invertebrates that are considered to be pests in agriculture and to people in general.
Due to a fast metabolic rate the shrew is an aggressive hunter and very active. A captive shrew eats about 75% of its body weight each day. In the desert shrews consume large quantities of invertebrates including worms, spiders, insects and possibly small mammals, lizards, or birds whenever able to catch them. For the most part this shrew feeds on insect larve and adults. Notiosorex crawfordi is common near water and is known to drink, but it is also capable of obtaining water from its prey.
Notiosorex crawfordi ranges from southern California east through eastern Arizona and from southern Colorado to the western edges of Texas and Arkansas. The shrew also ranges into the northern deserts of Central America.
Biogeographic Regions: nearctic (Native )
Desert shrews are found in arid areas but are not restricted to any particular habitat. Specimens have been taken in cattail marshes, in beehives, wood rat nests, among yuccas, under piles of cornstalks, and beneath piles of refuse and brush left by people. The shrew lives in elevations as high as 6,300 ft. At lower elevations the shrew will be found in humid microclimates such as in burrows or under rocks.
Terrestrial Biomes: desert or dune ; chaparral
Notiosorex crawfordi is a small shrew averaging 81 mm in length. The tail is greater than twice the lenth of the hind feet. The body has gray fur with some highlights of brown above. The underside is pale and gray. Sometimes this shrew can be pale and ashy in color. The tail is long and the ears are more noticable than on other shrews. The dental formula of the desert shrew is I 3/2, C 1/0, Pm 1/1, M 3/3. This is the only shrew in North America with 3 cheek teeth that have only one cusp on each tooth.
Range mass: 4.5 to 8 g.
Other Physical Features: endothermic ; bilateral symmetry
Notiosorex crawfordi can reach sexual maturity in two months of age. They are capable of having more than one litter a year if conditions are favorable. The female shrew makes a crude nest of fine grasses and other vegetation with some hair in a secluded area such as under a plant or board. The litter consists of 3 to 5 in a brood. These infants are born without hair and are blind. The young mature rapidly and may accompany the mother for a short time before venturing off on their own.
Key Reproductive Features: gonochoric/gonochoristic/dioecious (sexes separate); sexual
Crawford's gray shrew (Notiosorex crawfordi), also known as the desert shrew, is a small shrew found in the southwestern United States and northern Mexico. It is a member of the family Soricidae of the order Eulipotyphla. It was the only known member of the genus Notiosorex until two species, N. villai distributed in Tamaulipas, Mexico, and N. evotis distributed along the northwest coast of Mexico, were named.[3] A fourth distinct species, N. cockrumi, was discovered in Arizona and named in 2004.[4]
Crawford's gray shrew is one of the smallest desert mammals and one of the world's smallest homeotherms. When fully grown, it will only grow to a size of about 1.5 to 2 in (3.8 to 5.1 cm) long, half of which is the tail, and it will only grow to a weight of about 3 to 5 g (0.11 to 0.18 oz). It is gray-brown with light gray under parts. The long tail is gray with it being lighter underneath. It has small, but relatively prominent, ears.
A Crawford's gray shrew is born during the summer months to a litter size of three to six. When born, it is naked, pink and is about the same size as a honeybee. It grows rapidly and reaches its adult size in about four to five weeks. As a baby, its diet consists of milk the mother produces without the aid of water. After two to three weeks, its diet changes to food brought back to the nest and then regurgitated into the juvenile's mouth. By fall, Crawford's gray shrew is out of the nest and on its own. As an adult, its diet changes from the regurgitated food to intact food it kills itself. Crawford's gray shrew will eat lizards, small mice, and scorpions, but its main food source is a wide variety of arthropods. Since this shrew has a very high rate of metabolism, it will eat up to 75% of its body weight every day, and occasionally its full body weight. This can be dangerous since it can overheat the animal. The heat produced by metabolism and gained from its surrounding environment results in a high risk of overheating.
The shrew spends energy at very fast pace. When resting, the average shrew's heart rate is at about 1000 bit/s (beats per minute). In its respiratory rate, that is 800 breaths per minute.
The breeding season of the Crawford's gray shrew ranges from the spring to the fall to year-round. About three weeks after mating, the female shrew will give birth to three to five offspring.
The Crawford's gray shrew has poor vision, so it uses its highly sensitive ears and long nose to hunt down its prey. It will also use an echolocation, similar to bats, with high-pitched squeaks to locate prey. The shrews store food during the night so they don't have to go out during the day.
When threatened, the gray shrew can emit a musky odor that makes it seem less appetizing to mammalian predators.
Because of its diet, the Crawford's gray shrew must expel a large amount of nitrogenous waste from its body, which has a potential for a large loss of water when urinating. However, it is able to reduce water loss from urine, as well, by concentrating urea in the urine. The urine is four times more concentrated than that of a human, thus saving a huge amount of water.
This species also conserves water by being nocturnal, unlike other shrews, which hunt day and night to avoid starvation. To keep from losing any water from its victims, it will bite off the legs and then crush the prey's head so as not to kill it but to keep it fresh and unable to move.
Since water loss is a huge problem for this shrew, it has adapted by reducing two major causes of water loss. While breathing, Crawford's gray shrew inhales air warmed to body temperature and absorbs water vapor from the nasal walls. Exhaled air is cooled as the air is exiting, and the water vapor from the air condenses on the nasal passage. This keeps in more water than if the air were exhaled at body temperature. Water loss is reduced even more through respiration because it takes fewer breaths than other shrews and it has the lowest resting metabolic rate of all shrew species.
Crawford's gray shrew, unlike most shrews, do not have access to an abundant water supply. To conserve the little water that shrews do absorb, they find shelter to protect them from the harsh external temperatures. Crawford's gray shrew does not construct its own burrows or use the ones made by other animals. Instead, it builds small nests in pack rat houses or under dead agaves.
Even with all of these adaptations to help it survive in the harsh environment of the desert, Crawford gray shrew only lives for a relatively short period (about a year or so in the wild). Since it hunts at night, Crawford's gray shrew is susceptible to nocturnal hunters, such as snakes and owls.
As the shrew feeds on insects and intakes more food than their body mass within a short period, when deprived of food, the gray shrew will starve to death in hours.
Crawford's gray shrew (Notiosorex crawfordi), also known as the desert shrew, is a small shrew found in the southwestern United States and northern Mexico. It is a member of the family Soricidae of the order Eulipotyphla. It was the only known member of the genus Notiosorex until two species, N. villai distributed in Tamaulipas, Mexico, and N. evotis distributed along the northwest coast of Mexico, were named. A fourth distinct species, N. cockrumi, was discovered in Arizona and named in 2004.
