Crawford's gray shrew (''Notiosorex crawfordi''), also known as the desert shrew, is a small
shrew
Shrews (family Soricidae) are small mole-like mammals classified in the order Eulipotyphla. True shrews are not to be confused with treeshrews, otter shrews, elephant shrews, West Indies shrews, or marsupial shrews, which belong to differ ...
found in the
southwestern United States and northern
Mexico
Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...
. It is a member of the family
Soricidae of the order
Eulipotyphla
Eulipotyphla (, which means "truly fat and blind") is an order of mammals suggested by molecular methods of phylogenetic reconstruction, which includes the laurasiatherian members of the now-invalid polyphyletic order Lipotyphla, but not the ...
. It was the only known member of the genus ''
Notiosorex'' until two species, ''N. villai'' distributed in
Tamaulipas
Tamaulipas (), officially the Free and Sovereign State of Tamaulipas ( es, Estado Libre y Soberano de Tamaulipas), is a state in the northeast region of Mexico; one of the 31 states which, along with Mexico City, comprise the 32 Federal Entiti ...
,
Mexico
Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...
, and ''N. evotis'' distributed along the northwest coast of
Mexico
Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...
, were named.
A fourth distinct species, ''N. cockrumi'', was discovered in
Arizona
Arizona ( ; nv, Hoozdo Hahoodzo ; ood, Alĭ ṣonak ) is a state in the Southwestern United States. It is the 6th largest and the 14th most populous of the 50 states. Its capital and largest city is Phoenix. Arizona is part of the Fou ...
and named in 2004.
Description
Crawford's gray shrew is one of the smallest
desert mammals and one of the world's smallest
homeotherm
Homeothermy, homothermy or homoiothermy is thermoregulation that maintains a stable internal body temperature regardless of external influence. This internal body temperature is often, though not necessarily, higher than the immediate environmen ...
s. When fully grown, it will only grow to a size of about long, half of which is the tail, and it will only grow to a weight of about . 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
A honey bee (also spelled honeybee) is a eusocial flying insect within the genus ''Apis'' of the bee clade, all native to Afro-Eurasia. After bees spread naturally throughout Africa and Eurasia, humans became responsible for the current cosm ...
. 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
arthropod
Arthropods (, (gen. ποδός)) are invertebrate animals with an exoskeleton, a segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and cuticle made of chiti ...
s. Since this shrew has a very high rate of
metabolism
Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run c ...
, 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.
Characteristics
The shrew spends energy at very fast pace. When resting, the average shrew's heart rate is at about 1000 bps (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.
Water Loss
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
Urea, also known as carbamide, is an organic compound with chemical formula . This amide has two amino groups (–) joined by a carbonyl functional group (–C(=O)–). It is thus the simplest amide of carbamic acid.
Urea serves an important ...
in the
urine
Urine is a liquid by-product of metabolism in humans and in many other animals. Urine flows from the kidneys through the ureters to the urinary bladder. Urination results in urine being excreted from the body through the urethra.
Cellular ...
. 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.
Shelter
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
A pack rat or packrat, also called a woodrat or trade rat, are any species in the North and Central American rodent genus ''Neotoma''. Pack rats have a rat-like appearance, with long tails, large ears, and large, black eyes. Pack rats are notice ...
houses or under dead
agave
''Agave'' (; ; ) is a genus of monocots native to the hot and arid regions of the Americas and the Caribbean, although some ''Agave'' species are also native to tropical areas of North America, such as Mexico. The genus is primarily known for ...
s.
Lifespan
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
snake
Snakes are elongated, limbless, carnivorous reptiles of the suborder Serpentes . Like all other squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales. Many species of snakes have skulls with several more j ...
s and
owl
Owls are birds from the order Strigiformes (), which includes over 200 species of mostly solitary and nocturnal birds of prey typified by an upright stance, a large, broad head, binocular vision, binaural hearing, sharp talons, and feathers a ...
s.
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.
References
{{Taxonbar, from=Q1762293
Crawford's Gray Shrew
Fauna of the Southwestern United States
Fauna is all of the animal life present in a particular region or time. The corresponding term for plants is ''flora'', and for fungi, it is ''funga''. Flora, fauna, funga and other forms of life are collectively referred to as '' biota''. Zool ...
Mammals of the United States
Mammals of Mexico
Mammals described in 1877