Notiosorex crawfordi

Crawford's Gray Shrew

Crawford's Gray Shrew, Notiosorex crawfordi, is a small shrew that can be found in the southwestern United States and northern Mexico. It is a member of the Order Soricomorpha and the Family Soricidae . It is was the only known member of the genus Notiosorex until 2 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. 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 one and a half to two inches long, half of which is the tail and it will only grow to a weight of about 3 to 5 grams. It is a 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, Crawford's Gray Shrew 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 that the mother produces without the aid of water. After two to three weeks, the diet is changed into food that is brought back to the nest and then regurgitated into the juvenile's mouth. By the time fall rolls around, Crawford's Gray Shrew is out of the nest and is on its own. As an adult, the diet changes from the regurgitation of food to real food that it kills itself. Crawford's Gray Shrew will eat lizards, small mice, and scorpions. The main food source for Crawford's Gray Shrew, though, is a wide variety of arthropods. Since Crawford's Gray Shrew has a very high rate of metabolism, it will eat up to 75 percent of its body weight every day. A few rare occurrences have been known where it will eat its full ody weight in a single day; this can be dangerous since it can overheat the animal. The amount of heat produced by the high rate of metabolism and the heat gained from its surrounding environment will give a high risk of overheating.

Crawford's Gray Shrew, unlike most shrews, does not have access to an abundant water supply. To conserve the little water that shrews do absorb is to find shelter that will protect them from the harsh external temperatures. Crawford's Gray Shrew does not construct its own burrow or use the ones made by other animals. Instead, it builds small nests that can be found in packrat houses or under dead agaves.

Another way Crawford's Gray Shrew will conserve its precious water is by doing most of its activities at night. This is also an odd behavior among shrews, since most will hunt day and night since it does not take long for a shrew to starve to death. 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 a tactic similar to that of a bat and use echolocation with high-pitched squeaks to hunt down prey. It will then compile a large amount of food during the night so it will not have to go out during the day. To keep from losing any water from its victims, Crawford's Gray Shrew 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 Crawford's Gray Shrew, it has adapted by reducing two major paths of water loss. One of these ways is through respiratory. While breathing, Crawford's Gray Shrew will inhale air that will be warmed to body temperature and will absorb water vapor from the nasal walls. Exhaled air is cooled and so as the air is exiting the water vapor from the air clings to the nasal passage. This keeps in more water vapor than if the air was exhaled at body temperature. Water loss is reduced even more through respiration because Crawford's Gray Shrew takes fewer breaths than other shrews and it has the lowest resting metabolic rate of all shrew species.

The other form of reducing water loss is through the form of urine. Crawford's Gray Shrew has to expel a large amount of nitrogenous waste from its body. This is a potential for a large loss of water when urinating. Fortunately, Crawford's Gray Shrew is able to reduce the amount of water loss during this action as well. It does this by concentrating a large amount of urea in their urine. When urea is being concentrated it uses basically the same principle as conserving water while breathing. The end result of all this concentration is urine that is four times more concentrated than that of a human. Since it takes only a few drops of urine to expel all the waste from a Crawford's Gray Shrew in one day, this saves a huge amount of water.

Even with all of these adaptations to help Crawford's Gray Shrew to survive in the harsh environment of the desert, it still only lives for a relatively short time. Since it hunts at night, Crawford's Gray Shrew is susceptible to nocturnal hunters such as snakes and owls. Although it can emit a musky odor that makes it seem less appetizing to mammalian predators it still lives for only about a year or so in the wild.

References

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