Northern Short-tailed Shrew
Encyclopedia
The Northern Short-tailed Shrew (Blarina brevicauda) is the largest shrew
in the genus Blarina, and occurs in the northeastern region of North America
. It is a semifossorial
, highly active and voracious insectivore
and is present in a variety of habitats. It is notable in that it is one of the few venomous mammals
. The specific epithet, brevicauda, is a combination of the Latin
brevis and cauda, meaning "short tail".
, one of three or four species
(depending on the authority) in the genus Blarina. It was formerly considered to be a sister subspecies
of the Southern Short-tailed Shrew
(Blarina carolinensis). The species has been divided into eleven subspecies based on morphological
characteristics, which are grouped into two semi-species: brevicauda and talpoides. These groupings were mirrored by a molecular systematics study of the mitochondrial
cytochrome b
sequence. The two groups of subspecies are thought to have been kept isolated from each other by Pleistocene
glacier
s.
This shrew has a total length of 108 to 140 mm (4.3 to 5.5 inches), of which 18 to 32 mm (0.7 to 1.3 inches) is tail; and weighs 15 to 30 grams (0.5 to 1.1 ounces). The Northern Short-tailed Shrew exhibits slight sexual dimorphism
in size, with the male being slightly larger than the female. The dorsal
fur is thick and velvety, and can be black, brownish black, or silvery gray, with the ventral fur being a bit lighter and grayer. The shrew molts from a summer coat, which is shorter and paler than the winter pelage in October and November, and back again sometime in February through July. The tail is quite short, amounting to less than 25% of the total length. The species has one upper incisor
, five unicuspids (simple teeth that cannot be easily identified), a premolar
(the fourth), and three molars in the upper jaw. The lower dentition is identical, except that there is only one unicuspid. Three well-developed scent gland
s are present, one on each side of the animal and one ventral. The scent may be used for marking territories, though the shrew's sense of smell is thought to be poor.
, though one record from the late Pliocene
(Blancan
land mammal age) is tentatively attributed to this species. Another source indicates that the earliest record of the genus Blarina is a specimen of the talpoides subspecies of B. brevicauda, from the Blancan
(early Pleistocene
) in Kansas
. The species is thought to have arisen in the middle or late Pliocene
. The brevicauda subspecies appeared later.
, from southern Saskatchewan
to Atlantic Canada
and south to Nebraska
and Georgia
. It is probably the most common shrew in the Great Lakes
region. Population densities usually range from 5-30 shrews per hectare (2-12 per acre), but rarely exceed 200 per hectare
(80 per acre). The typical home range of a shrew is 2.5 hectares, and may overlap slightly with the ranges of other shrews.
and coniferous forests, and household gardens, though the preferred habitats are moist with a decent amount of leaf litter or thick plant cover. Burned-over forests are not quickly recolonized by B. brevicauda, and shrews quickly depart clear-cuts.
and seeds, though it is mostly carnivorous
. It prefers insects, earthworm
s, vole
s, snails, and other shrews for the bulk of the diet, though salamander
s and mice
are also eaten. This shrew consumes vertebrate
s more often than other shrews do. The shrew mostly forages within a few hours after sunset, though it is also active during cloudy days. High evaporative water loss requires the shrew to have access to a source of water, though it does obtain water from its food as well. The shrew often hoards food, especially in the fall and winter, or during a time of prey abundance. one study found that it caches 87% of the prey it catches, while 9% is eaten immediately and 4% is left where it was killed.
of the Northern Short-tailed Shrew contains a kallikrein
-like protease
, used to paralyze
and subdue its prey. The toxin is strong enough to kill small animals, up to sizes somewhat larger than the shrew itself, and results in painful bites to humans who attempt to handle the shrew. The poisonous saliva is secreted from submaxillary glands
, through a duct at the base of the lower incisor
s, where the saliva flows along the groove formed by the two incisors, and into the prey. The toxin is very similar in structure to the one used by the Mexican beaded lizard (Heloderma horridum), but evolved independently, however from the same precursor protein.
One of the venom component, a peptide called Soricidin, has been patented and is being investigated in Canada for pain control and as an anti-cancer drug. Another component is being studied in Japan as an anti-hypertensive agent.
and a fine sense of touch.
.
The shrew constructs a nest up to 20 centimeters (8 inches) in diameter underground or underneath a log, and lines it with leaves or the fur of the Meadow Vole
(Microtus pennsylvanicus). This nest is kept clean, with wastes deposited outside the nest in a latrine area. Other parts of the burrow system are used for food storage.
Typically solitary, B. brevicauda exhibits several aggressive displays and vocalizations
to ward off other members of the species when encounters occur. Pairs of shrews introduced to a cage simultaneously coexisted for less than four months before one killed the other, and a new shrew placed in a cage containing an already established shrew is killed within a few hours.
s, raptor
s, canids, cat
s, mustelids, skunk
s, raccoon
s, and opossums, though mammal
ian carnivore
s appear to be deterred by the musky odor produced by the shrew's scent glands.
, as it is widespread, abundant, and its population is not declining.
Shrew
A shrew or shrew mouse is a small molelike mammal classified in the order Soricomorpha. True shrews are also not to be confused with West Indies shrews, treeshrews, otter shrews, or elephant shrews, which belong to different families or orders.Although its external appearance is generally that of...
in the genus Blarina, and occurs in the northeastern region of North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
. It is a semifossorial
Fossorial
A fossorial organism is one that is adapted to digging and life underground such as the badger, the naked mole rat, and the mole salamanders Ambystomatidae...
, highly active and voracious insectivore
Insectivore
An insectivore is a type of carnivore with a diet that consists chiefly of insects and similar small creatures. An alternate term is entomophage, which also refers to the human practice of eating insects....
and is present in a variety of habitats. It is notable in that it is one of the few venomous mammals
Venomous mammals
Venomous mammals are animals of the class Mammalia that produce venom, which they use to kill or disable prey, or to defend themselves from predators. In modern nature, venomous mammals are quite rare. Venom is much more common among other vertebrates; there are many more species of venomous...
. The specific epithet, brevicauda, is a combination of the Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
brevis and cauda, meaning "short tail".
Taxonomy
Blarina brevicauda is a red-toothed shrewRed-toothed shrew
The red-toothed shrews of the subfamily Soricinae are one of three living subfamilies of shrews, along with Crocidurinae and Myosoricinae . In addition, the family contains the extinct subfamilies Limnoecinae, Crocidosoricinae, Allosoricinae and Heterosoricinae...
, one of three or four species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
(depending on the authority) in the genus Blarina. It was formerly considered to be a sister subspecies
Subspecies
Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...
of the Southern Short-tailed Shrew
Southern Short-tailed Shrew
The Southern Short-tailed Shrew is a small, gray, short-tailed mammal that inhabits the eastern United States. The overall appearance is somewhat like a rodent, but is a member of the order Soricomorpha and should not be confused with a member of the order Rodentia. This shrew has a long, pointed...
(Blarina carolinensis). The species has been divided into eleven subspecies based on morphological
Morphology (biology)
In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....
characteristics, which are grouped into two semi-species: brevicauda and talpoides. These groupings were mirrored by a molecular systematics study of the mitochondrial
Mitochondrion
In cell biology, a mitochondrion is a membrane-enclosed organelle found in most eukaryotic cells. These organelles range from 0.5 to 1.0 micrometers in diameter...
cytochrome b
Cytochrome b
Cytochrome b/b6 is the main subunit of transmembrane cytochrome bc1 and b6f complexes. In addition, it commonly refers to a region of mtDNA used for population genetics and phylogenetics.- Function :...
sequence. The two groups of subspecies are thought to have been kept isolated from each other by Pleistocene
Pleistocene
The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....
glacier
Glacier
A glacier is a large persistent body of ice that forms where the accumulation of snow exceeds its ablation over many years, often centuries. At least 0.1 km² in area and 50 m thick, but often much larger, a glacier slowly deforms and flows due to stresses induced by its weight...
s.
Description
Sexual dimorphism
Sexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...
in size, with the male being slightly larger than the female. The dorsal
Dorsum (biology)
In anatomy, the dorsum is the upper side of animals that typically run, fly, or swim in a horizontal position, and the back side of animals that walk upright. In vertebrates the dorsum contains the backbone. The term dorsal refers to anatomical structures that are either situated toward or grow...
fur is thick and velvety, and can be black, brownish black, or silvery gray, with the ventral fur being a bit lighter and grayer. The shrew molts from a summer coat, which is shorter and paler than the winter pelage in October and November, and back again sometime in February through July. The tail is quite short, amounting to less than 25% of the total length. The species has one upper incisor
Incisor
Incisors are the first kind of tooth in heterodont mammals. They are located in the premaxilla above and mandible below.-Function:...
, five unicuspids (simple teeth that cannot be easily identified), a premolar
Premolar
The premolar teeth or bicuspids are transitional teeth located between the canine and molar teeth. In humans, there are two premolars per quadrant, making eight premolars total in the mouth. They have at least two cusps. Premolars can be considered as a 'transitional tooth' during chewing, or...
(the fourth), and three molars in the upper jaw. The lower dentition is identical, except that there is only one unicuspid. Three well-developed scent gland
Scent gland
Scent glands are found in the genital area of most mammals and in various other parts of the body, such as the underarms of humans and the preorbital glands of deer and muskox. They produce a semi-viscous fluid which contains pheromones. These odor-messengers indicate information such as status,...
s are present, one on each side of the animal and one ventral. The scent may be used for marking territories, though the shrew's sense of smell is thought to be poor.
Fossil Record
Most records of B. brevicauda are from the PleistocenePleistocene
The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....
, though one record from the late Pliocene
Pliocene
The Pliocene Epoch is the period in the geologic timescale that extends from 5.332 million to 2.588 million years before present. It is the second and youngest epoch of the Neogene Period in the Cenozoic Era. The Pliocene follows the Miocene Epoch and is followed by the Pleistocene Epoch...
(Blancan
Blancan
The Blancan North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology , typically set from 4,750,000 to 1,808,000 years BP, a period of .. It is usually considered to start in the early-mid Pliocene epoch and end...
land mammal age) is tentatively attributed to this species. Another source indicates that the earliest record of the genus Blarina is a specimen of the talpoides subspecies of B. brevicauda, from the Blancan
Blancan
The Blancan North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology , typically set from 4,750,000 to 1,808,000 years BP, a period of .. It is usually considered to start in the early-mid Pliocene epoch and end...
(early Pleistocene
Pleistocene
The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....
) in Kansas
Kansas
Kansas is a US state located in the Midwestern United States. It is named after the Kansas River which flows through it, which in turn was named after the Kansa Native American tribe, which inhabited the area. The tribe's name is often said to mean "people of the wind" or "people of the south...
. The species is thought to have arisen in the middle or late Pliocene
Pliocene
The Pliocene Epoch is the period in the geologic timescale that extends from 5.332 million to 2.588 million years before present. It is the second and youngest epoch of the Neogene Period in the Cenozoic Era. The Pliocene follows the Miocene Epoch and is followed by the Pleistocene Epoch...
. The brevicauda subspecies appeared later.
Range
This shrew is found throughout central and eastern North AmericaNorth America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
, from southern Saskatchewan
Saskatchewan
Saskatchewan is a prairie province in Canada, which has an area of . Saskatchewan is bordered on the west by Alberta, on the north by the Northwest Territories, on the east by Manitoba, and on the south by the U.S. states of Montana and North Dakota....
to Atlantic Canada
Atlantic Canada
Atlantic Canada is the region of Canada comprising the four provinces located on the Atlantic coast, excluding Quebec: the three Maritime provinces – New Brunswick, Prince Edward Island, and Nova Scotia – and Newfoundland and Labrador...
and south to Nebraska
Nebraska
Nebraska is a state on the Great Plains of the Midwestern United States. The state's capital is Lincoln and its largest city is Omaha, on the Missouri River....
and Georgia
Georgia (U.S. state)
Georgia is a state located in the southeastern United States. It was established in 1732, the last of the original Thirteen Colonies. The state is named after King George II of Great Britain. Georgia was the fourth state to ratify the United States Constitution, on January 2, 1788...
. It is probably the most common shrew in the Great Lakes
Great Lakes
The Great Lakes are a collection of freshwater lakes located in northeastern North America, on the Canada – United States border. Consisting of Lakes Superior, Michigan, Huron, Erie, and Ontario, they form the largest group of freshwater lakes on Earth by total surface, coming in second by volume...
region. Population densities usually range from 5-30 shrews per hectare (2-12 per acre), but rarely exceed 200 per hectare
Hectare
The hectare is a metric unit of area defined as 10,000 square metres , and primarily used in the measurement of land. In 1795, when the metric system was introduced, the are was defined as being 100 square metres and the hectare was thus 100 ares or 1/100 km2...
(80 per acre). The typical home range of a shrew is 2.5 hectares, and may overlap slightly with the ranges of other shrews.
Habitat
Both disturbed and undisturbed habitats are used by the Northern Short-tailed Shrew, including grasslands, old fields, fencerows, marshy areas, deciduousDeciduous
Deciduous means "falling off at maturity" or "tending to fall off", and is typically used in reference to trees or shrubs that lose their leaves seasonally, and to the shedding of other plant structures such as petals after flowering or fruit when ripe...
and coniferous forests, and household gardens, though the preferred habitats are moist with a decent amount of leaf litter or thick plant cover. Burned-over forests are not quickly recolonized by B. brevicauda, and shrews quickly depart clear-cuts.
Diet
The Northern Short-tailed Shrew consumes up to three times its weight in food each day. It eats small quantities of subterranean fungiFungus
A fungus is a member of a large group of eukaryotic organisms that includes microorganisms such as yeasts and molds , as well as the more familiar mushrooms. These organisms are classified as a kingdom, Fungi, which is separate from plants, animals, and bacteria...
and seeds, though it is mostly carnivorous
Carnivore
A carnivore meaning 'meat eater' is an organism that derives its energy and nutrient requirements from a diet consisting mainly or exclusively of animal tissue, whether through predation or scavenging...
. It prefers insects, earthworm
Earthworm
Earthworm is the common name for the largest members of Oligochaeta in the phylum Annelida. In classical systems they were placed in the order Opisthopora, on the basis of the male pores opening posterior to the female pores, even though the internal male segments are anterior to the female...
s, vole
Vole
A vole is a small rodent resembling a mouse but with a stouter body, a shorter hairy tail, a slightly rounder head, smaller ears and eyes, and differently formed molars . There are approximately 155 species of voles. They are sometimes known as meadow mice or field mice in North America...
s, snails, and other shrews for the bulk of the diet, though salamander
Salamander
Salamander is a common name of approximately 500 species of amphibians. They are typically characterized by a superficially lizard-like appearance, with their slender bodies, short noses, and long tails. All known fossils and extinct species fall under the order Caudata, while sometimes the extant...
s and mice
Mouse
A mouse is a small mammal belonging to the order of rodents. The best known mouse species is the common house mouse . It is also a popular pet. In some places, certain kinds of field mice are also common. This rodent is eaten by large birds such as hawks and eagles...
are also eaten. This shrew consumes vertebrate
Vertebrate
Vertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...
s more often than other shrews do. The shrew mostly forages within a few hours after sunset, though it is also active during cloudy days. High evaporative water loss requires the shrew to have access to a source of water, though it does obtain water from its food as well. The shrew often hoards food, especially in the fall and winter, or during a time of prey abundance. one study found that it caches 87% of the prey it catches, while 9% is eaten immediately and 4% is left where it was killed.
Toxin
The salivaSaliva
Saliva , referred to in various contexts as spit, spittle, drivel, drool, or slobber, is the watery substance produced in the mouths of humans and most other animals. Saliva is a component of oral fluid. In mammals, saliva is produced in and secreted from the three pairs of major salivary glands,...
of the Northern Short-tailed Shrew contains a kallikrein
Kallikrein
Kallikreins are a subgroup of serine proteases, enzymes capable of cleaving peptide bonds in proteins. In humans, plasma kallikrein has no known homologue, while tissue kallikrein-related peptidases encode a family of fifteen closely related serine proteases...
-like protease
Protease
A protease is any enzyme that conducts proteolysis, that is, begins protein catabolism by hydrolysis of the peptide bonds that link amino acids together in the polypeptide chain forming the protein....
, used to paralyze
Paralysis
Paralysis is loss of muscle function for one or more muscles. Paralysis can be accompanied by a loss of feeling in the affected area if there is sensory damage as well as motor. A study conducted by the Christopher & Dana Reeve Foundation, suggests that about 1 in 50 people have been diagnosed...
and subdue its prey. The toxin is strong enough to kill small animals, up to sizes somewhat larger than the shrew itself, and results in painful bites to humans who attempt to handle the shrew. The poisonous saliva is secreted from submaxillary glands
Submandibular gland
The paired submandibular glands are salivary glands located beneath the floor of the mouth. In humans, they account for 70% of the salivary volume and weigh about 15 grams. Unstimulated in humans, the percentage contribution to whole saliva; ~25% Parotid, Submandibular and Sublingual ~ 67% and...
, through a duct at the base of the lower incisor
Incisor
Incisors are the first kind of tooth in heterodont mammals. They are located in the premaxilla above and mandible below.-Function:...
s, where the saliva flows along the groove formed by the two incisors, and into the prey. The toxin is very similar in structure to the one used by the Mexican beaded lizard (Heloderma horridum), but evolved independently, however from the same precursor protein.
One of the venom component, a peptide called Soricidin, has been patented and is being investigated in Canada for pain control and as an anti-cancer drug. Another component is being studied in Japan as an anti-hypertensive agent.
Senses
The sense of smell is thought to be poor, and the eyes are degenerate and vision is thought to be limited to the detection of light, but the shrew compensates by using echolocationAnimal echolocation
Echolocation, also called biosonar, is the biological sonar used by several kinds of animals.Echolocating animals emit calls out to the environment and listen to the echoes of those calls that return from various objects near them. They use these echoes to locate and identify the objects...
and a fine sense of touch.
Energetics
Its ability to consume almost anything it can catch allows the Northern Short-tailed Shrew to survive the cold winters of temperate regions. The thermoneutral zone of this species is from 25 to 33 degrees Celsius—meaning that no extra energy must be expended by the animal to maintain its body temperature (which averages 38–38.5 degrees Celsius) when the ambient temperature is within this range. Food consumption is 43% higher in winter than in summer, as the shrew must increase its metabolic rate in order to maintain its body temperature under the cold conditions. Temperatures at or above 35 degrees Celsius are lethal for this shrew. A study of captive shrews found that though they were primarily nocturnal, the degree of nocturnality changed with the season. That is, during the colder winter months the shrews exhibited more out-of-burrow activity earlier in the evening, but were active later in the night during the summer. The study indicated that this seasonal pattern was due to solar radiation and changing daily temperatures, and that it allows the shrews to minimize the energy needed for thermoregulation. Other winter adaptations include the creation of a lined nest, which helps the shrew conserve heat, caching of food in case of prey shortages, foraging below the leaf litter or snow where the temperature is milder, and decreasing activity levels during cold periods. Along with these behavioral adaptations, the Northern Short-tailed Shrew increases its ability to generate body heat during the winter by nonshivering thermogenesis in brown adipose tissueBrown adipose tissue
Brown adipose tissue or brown fat is one of two types of fat or adipose tissue found in mammals....
.
Behavior
Other shrews spend more time above ground than does the Northern Short-tailed Shrew, which prefers to tunnel along below ground, through the leaf litter, or at the snow/ground interface. Bouts of frenzied activity, lasting approximately five minutes, are followed by longer periods of resting, with the total active time amounting to only 16% of a 24-hour day. This animal is capable of digging at a rate of 2.5 centimeters per minute, in-between resting.The shrew constructs a nest up to 20 centimeters (8 inches) in diameter underground or underneath a log, and lines it with leaves or the fur of the Meadow Vole
Meadow Vole
The Meadow Vole , sometimes called the Field Mouse or Meadow Mouse, is a North American vole found across Canada, Alaska and the northern United States. Its range extends further south along the Atlantic coast. One subspecies, the Florida Salt Marsh Vole , is found in Florida, and is classified as...
(Microtus pennsylvanicus). This nest is kept clean, with wastes deposited outside the nest in a latrine area. Other parts of the burrow system are used for food storage.
Typically solitary, B. brevicauda exhibits several aggressive displays and vocalizations
Animal communication
Animal communication is any behavior on the part of one animal that has an effect on the current or future behaviour of another animal. The study of animal communication, is sometimes called Zoosemiotics has played an important part in the...
to ward off other members of the species when encounters occur. Pairs of shrews introduced to a cage simultaneously coexisted for less than four months before one killed the other, and a new shrew placed in a cage containing an already established shrew is killed within a few hours.
Reproduction
Mating occurs from March through September, though most births occur early or late in that period. B. brevicauda is promiscuous. Male shrews in captivity were observed to make clicking sounds while courting a female. During copulation the male and female are locked together, and the female drags the male along with her. Gestation lasts 21–22 days, and after birth the 4-7 young are suckled for up to 25 days. Two litters per season are typical, though three is possible. The female strengthens the nest when the young are lactating, and is more active to support her increased nutritional needs. The young, which were born hairless and blind, weighing less than a gram, may become sexually mature in as soon as 2–3 months. Those born in the spring mature more quickly than those born late in the season, and may themselves reproduce in the same year that they were born. The juvenile pelage is pale and quite similar to the adults' summer fur, and is molted when the young reaches adult size.Predation
The Northern Short-tailed Shrew has a high mortality rate, though it attempts to escape predation by remaining hidden under vegetation, soil, leaf litter, or snow; in a study only 6% of a marked group of shrews survived to the next year, and winter mortality of 90% has been recorded, probably due to cold stress. This shrew is consumed by many predators: snakeSnake
Snakes are elongate, legless, carnivorous reptiles of the suborder Serpentes that can be distinguished from legless lizards by their lack of eyelids and external ears. Like all squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales...
s, raptor
Bird of prey
Birds of prey are birds that hunt for food primarily on the wing, using their keen senses, especially vision. They are defined as birds that primarily hunt vertebrates, including other birds. Their talons and beaks tend to be relatively large, powerful and adapted for tearing and/or piercing flesh....
s, canids, cat
Cat
The cat , also known as the domestic cat or housecat to distinguish it from other felids and felines, is a small, usually furry, domesticated, carnivorous mammal that is valued by humans for its companionship and for its ability to hunt vermin and household pests...
s, mustelids, skunk
Skunk
Skunks are mammals best known for their ability to secrete a liquid with a strong, foul odor. General appearance varies from species to species, from black-and-white to brown or cream colored. Skunks belong to the family Mephitidae and to the order Carnivora...
s, raccoon
Raccoon
Procyon is a genus of nocturnal mammals, comprising three species commonly known as raccoons, in the family Procyonidae. The most familiar species, the common raccoon , is often known simply as "the" raccoon, as the two other raccoon species in the genus are native only to the tropics and are...
s, and opossums, though mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...
ian carnivore
Carnivore
A carnivore meaning 'meat eater' is an organism that derives its energy and nutrient requirements from a diet consisting mainly or exclusively of animal tissue, whether through predation or scavenging...
s appear to be deterred by the musky odor produced by the shrew's scent glands.
Conservation
The Northern Short-tailed Shrew is considered a species of least concern in the IUCN Red ListIUCN Red List
The IUCN Red List of Threatened Species , founded in 1963, is the world's most comprehensive inventory of the global conservation status of biological species. The International Union for Conservation of Nature is the world's main authority on the conservation status of species...
, as it is widespread, abundant, and its population is not declining.