Northern short-tailed shrew

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Northern short-tailed shrew [1]
Blarina brevicauda.jpg
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Eulipotyphla
Family: Soricidae
Genus: Blarina
Species:
B. brevicauda
Binomial name
Blarina brevicauda
(Say, 1823)
Northern Short-tailed Shrew area.png

The northern short-tailed shrew (Blarina brevicauda) is the largest shrew in the genus Blarina , [3] and occurs in the northeastern region of North America. [4] It is a semifossorial, highly active, and voracious insectivore and is present in a variety of habitats like broadleaved and pine forests among shrubs and hedges as well as grassy river banks. [5] 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". [3]

Contents

Taxonomy

B. brevicauda is a red-toothed shrew, one of three or four species (depending on the authority) [3] in the genus Blarina. It was formerly considered to be a sister subspecies of the southern short-tailed shrew (B. carolinensis). [3] The species has been divided into 11 subspecies based on morphological characteristics, which are grouped into two semispecies: B. b. brevicauda and B. b. talpoides; these groupings were mirrored by a molecular systematics study of the mitochondrial cytochrome b sequence. [6] The two groups of subspecies are thought to have been kept isolated from each other by Pleistocene glaciers. [6]

Description

Northern short-tailed shrew Blarina brevicauda 2.jpg
Northern short-tailed shrew

This shrew has a total length of 108 to 140 mm (4.3 to 5.5 in), of which 18 to 32 mm (0.71 to 1.26 in) is tail; and weighs 15 to 30 g (0.53 to 1.06 oz). [5] The species exhibits slight sexual dimorphism in size, with the male being slightly larger than the female. [3] [4] 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. [5] 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. [3] The tail is quite short, amounting to less than 25% of the total length. [5] The dental formula is I 3-3/1-1, C 1-1/1-1, P 3-3/1-1, M 3-3/3-3 = 16/16 = 32. [3] Three well-developed scent glands 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. [3]

Distribution

Fossil record

Most records of B. brevicauda are from the Pleistocene, [7] though one record from the late Pliocene (Blancan land mammal age) is tentatively attributed to this species. [8] Another source indicates the earliest record of the genus Blarina is a specimen of B. b. talpoides, from the Blancan (early Pleistocene) in Kansas. The species is thought to have arisen in the middle or late Pliocene. [3] The B. b. brevicauda subspecies appeared later. [3]

Range

This shrew is found throughout central and eastern North America, from southern Saskatchewan to Atlantic Canada and south to northern Arkansas and Georgia. [4] [9] It is probably the most common shrew in the Great Lakes region. [3] [5] Population densities usually range from five to 30 shrews per hectare (two to 12 per acre), but rarely exceed 200/ha (80/ac). [5] The typical home range of a shrew is 2.5 ha, and may overlap slightly with the ranges of other shrews. [3]

Habitat

Both disturbed and undisturbed habitats are used by the northern short-tailed shrew, including grasslands, old fields, fencerows, marshy areas, deciduous and coniferous forests, and household gardens, [3] [4] [5] though the preferred habitats are those which are moist with leaf litter or thick plant cover. [3] [5] Burned-over forests are not quickly recolonized by B. brevicauda, [4] and shrews quickly depart clear-cuts. [3]

Diet

This shrew consumes up to three times its weight in food each day. [4] It eats small quantities of subterranean fungi and seeds, though it is mostly carnivorous. [5] It prefers insects, earthworms, voles, snails, and other shrews for the bulk of its diet, though salamanders and mice are also eaten. [5] This shrew consumes vertebrates more often than other shrews do. [5] The shrew mostly forages within a few hours after sunset, though it is also active during cloudy days. [5] 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. [3] The shrew often hoards food, especially in the fall and winter, or during a time of prey abundance; [3] one study found it caches 87% of the prey it catches, while 9% is eaten immediately and 4% is left where it was killed. [10]

Toxin

The saliva of the northern short-tailed shrew contains a kallikrein-like protease, used to paralyze and subdue its prey. [11] 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. [3] The venomous saliva is secreted from submaxillary glands, through a duct which opens at the base of the lower incisors, where the saliva flows along the groove formed by the two incisors, and into the prey. [3] [5] The toxin is very similar in structure to the one produced by the Mexican beaded lizard (Heloderma horridum) which independently developed its toxin from the same precursor protein. [12]

Physiology

Senses

Their sense of smell is thought to be poor, and their eyes are degenerated and vision is thought to be limited to the detection of light, [3] but the shrew compensates by using echolocation and a fine sense of touch. [4] [5]

Energetics

Its ability to consume almost anything it can catch allows the northern short-tailed shrew to survive the cold winters of temperate regions. [3] The thermoneutral zone of this species is from 25 to 33 °C, [3] meaning no extra energy must be expended by the animal to maintain its body temperature (which averages 38.0–38.5 °C [3] ) when the ambient temperature is within this range. Food consumption is 43% higher in winter than in summer, [3] as the shrew must increase its metabolic rate to maintain its body temperature under the cold conditions. Temperatures at or above 35 °C are lethal for this shrew. [3] A study of captive shrews found, though they were primarily nocturnal, the degree of nocturnality changed with the season; that is, during the colder winter, the shrews exhibited more out-of-burrow activity earlier in the evening, but were active later in the night during the summer. [13] This seasonal pattern was due to solar radiation and changing daily temperatures, and it allows the shrews to minimize the energy needed for thermoregulation. [13] Other winter adaptations include the creation of a lined nest which aids the shrew in conserving heat, the 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. [14] 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 tissue. [14]

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. [3] [5] Bouts of frenzied activity, lasting around five minutes, are followed by longer periods of resting, with the total active time amounting to only 16% of a 24-hour day. [3] This animal is capable of digging at a rate of 2.5 cm/min, in between resting. [3]

The shrew constructs a nest up to 20 cm (8 in) in diameter underground or underneath a log, and lines it with leaves or the fur of the meadow vole (Microtus pennsylvanicus). [3] [5] This nest is kept clean, with wastes deposited outside the nest in a latrine area. [3] [5] Other parts of the burrow system are used for food storage. [5]

Typically solitary, [4] B. brevicauda exhibits several aggressive displays and vocalizations to ward off other members of the species when encounters occur. [15] Pairs of shrews which were 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 will be killed within a few hours. [16]

Reproduction

Mating occurs from March through September, though most births occur early or late in that period. [5] Male shrews in captivity were observed to make clicking sounds while courting a female. [15] During copulation, the male and female are locked together, and the female drags the male along with her. [3] Gestation lasts 21–24 days, and after birth, the six to eight young are suckled for up to 25 days before the babies are weaned. [3] [5] Two litters per season are typical, though three are possible. [4] The female strengthens the nest when the young are nursing, and is more active to support her increased nutritional needs. [3] The young, which were born hairless and blind and 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 they were born. [3] [5] The juvenile pelage is pale and quite similar to the adults' summer fur, and is molted when the young reaches adult size. [3]

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; [4] only 6% of a marked group of shrews survived to the next year, [5] and winter mortality of 90% has been recorded, probably due to cold stress. [3] This shrew is consumed by many predators: trout, snakes, raptors, canids, cats, mustelids, skunks, raccoons, and opossums, [3] [5] though mammalian carnivores appear to be deterred by the musky odor produced by the shrew's scent glands. [5]

Conservation

The northern short-tailed shrew is considered a species of least concern in the IUCN Red List, as it is widespread, abundant, and its population is not declining. [2]

Relationship with humans

Northern short-tailed shrews cannot be domesticated. [17]

Related Research Articles

<span class="mw-page-title-main">Shrew</span> Family of mammals

Shrews 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 different families or orders.

<span class="mw-page-title-main">Common planigale</span> Species of marsupial

The common planigale, also known as the pygmy planigale or the coastal planigale, is one of many small marsupial carnivores known as "marsupial mice" found in Australia. There they fill a similar niche to the insectivores of other parts of the world.

<span class="mw-page-title-main">Rough-legged buzzard</span> Species of bird

The rough-legged buzzard (Europe) or rough-legged hawk is a medium-large bird of prey. It is found in Arctic and Subarctic regions of North America, Europe, and Russia during the breeding season and migrates south for the winter. It was traditionally also known as the rough-legged falcon in such works as John James Audubon's The Birds of America.

<span class="mw-page-title-main">Great horned owl</span> Species of owl

The great horned owl, also known as the tiger owl or the hoot owl, is a large owl native to the Americas. It is an extremely adaptable bird with a vast range and is the most widely distributed true owl in the Americas. Its primary diet is rabbits and hares, rats and mice, and voles, although it freely hunts any animal it can overtake, including rodents and other small mammals, larger mid-sized mammals, birds, reptiles, amphibians, and invertebrates.

<span class="mw-page-title-main">Broad-winged hawk</span> Species of bird

The broad-winged hawk is a medium-sized hawk of the genus Buteo. During the summer, some subspecies are distributed over eastern North America, as far west as British Columbia and Texas; they then migrate south to winter in the Neotropics from Mexico south to southern Brazil. Other subspecies are all-year residents on Caribbean islands. As in most raptors, females are slightly larger than males. Broad-winged hawks' wings are relatively short and broad with a tapered, somewhat pointed appearance. The two types of coloration are a dark morph with fewer white areas and a light morph that is more pale overall. Although the broad-winged hawk's numbers are relatively stable, populations are declining in some parts of its breeding range because of forest fragmentation.

<span class="mw-page-title-main">Etruscan shrew</span> Species of mammal

The Etruscan shrew, also known as the Etruscan pygmy shrew or the white-toothed pygmy shrew, is the smallest known extant mammal by mass, weighing only about 1.8 g (0.063 oz) on average.

<span class="mw-page-title-main">Cinereus shrew</span> Species of mammal

The cinereus shrew or masked shrew is a small shrew found in Alaska, Canada, and the northern United States. This is the most widely distributed shrew in North America, where it is also known as the common shrew.

<span class="mw-page-title-main">American pygmy shrew</span> Species of mammal

The American pygmy shrew is a small shrew found in Northern Alaska, Canada, and the northern United States, south through the Appalachian Mountains. It was first discovered in 1831 by naturalist William Cane in Georgian Bay, Parry Sound.

<span class="mw-page-title-main">North American least shrew</span> Species of mammal

The North American least shrew is one of the smallest mammals, growing to be only up to 3 inches long. It has a long pointed snout and a tail never more than twice the length of its hind foot. The dense fur coat is either grayish-brown or reddish-brown with a white belly. Its fur becomes lighter in the summer and darker in the winter. Although similar in appearance to several species of rodents, all shrews are members of the order Eulipotyphla and should not be mistaken for a member of the order Rodentia. The North American least shrew's eyes are small and its ears are completely concealed within its short fur, giving it very poor eyesight and hearing.

<span class="mw-page-title-main">Marsh shrew</span> Species of shrew

The marsh shrew, also known as the Pacific water shrew, Bendire's water shrew, Bendire's shrew and Jesus shrew is the largest North American member of the genus Sorex. Primarily covered in dark-brown fur, it is found near aquatic habitats along the Pacific coast from southern British Columbia to northern California. With air trapped in its fur for buoyancy, marsh shrews can run for three to five seconds on top of the water. It measures about 16 cm (6.3 in) in length, including a 7-centimetre (2.8 in)-long tail, and weighs an average of 14.5–16 g (0.51–0.56 oz). The marsh shrew's diet consists mainly of invertebrates, which it hunts on land and in the water. They are rare; their populations are thought to be in decline, and they are considered endangered in parts of their range.

<span class="mw-page-title-main">Southern short-tailed shrew</span> Species of mammal

The southern short-tailed shrew is a gray, short-tailed shrew that inhabits the eastern United States.

<span class="mw-page-title-main">Vagrant shrew</span> Species of mammal

The vagrant shrew, also known as the wandering shrew, is a medium-sized North American shrew. At one time, the montane shrew and the Orizaba long-tailed shrew were considered to belong to the same species.

<i>Blarina</i> Genus of mammals

The genus Blarina, commonly called short-tailed shrews, is a genus of relatively large shrews with relatively short tails found in North America.

<span class="mw-page-title-main">Eastern meadow vole</span> Species of mammal

The eastern meadow vole, sometimes called the field mouse or meadow mouse, is a North American vole found in eastern Canada and the United States. Its range extends farther south along the Atlantic coast.

<span class="mw-page-title-main">Eurasian water shrew</span> Species of mammal

The Eurasian water shrew, known in the United Kingdom as the water shrew, is a relatively large shrew, up to 10 cm (4 in) long, with a tail up to three-quarters as long again. It has short, dark fur, often with a few white tufts, a white belly, and a few stiff hairs around the feet and tail. It lives close to fresh water, hunting aquatic prey in the water and nearby. Its fur traps bubbles of air in the water which greatly aids its buoyancy, but requires it to anchor itself to remain underwater for more than the briefest of dives.

<span class="mw-page-title-main">Elliot's short-tailed shrew</span> Species of mammal

Elliot's short-tailed shrew is a small, slate grey, short-tailed species of shrew. Its common name comes from Daniel Giraud Elliot, who first described the species in 1899.

<span class="mw-page-title-main">Short-tailed field vole</span> Species of rodent

The short-tailed field vole, short-tailed vole, or simply field vole is a grey-brown vole, around 10 cm in length, with a short tail. It is one of the most common mammals in Europe, with a range extending from the Atlantic coast to Lake Baikal. These voles are found in moist grassy habitats, such as woodland, marsh or on river banks. Although they make shallow burrows, they usually build nests above ground. They are an important food source for owls and some other predators and their population size tends to peak and trough cyclically. Field voles breed prolifically, mainly in summer, but often all year round, even under snow. Females produce up to seven litters a year, each averaging from four to six young which are weaned after about fourteen days. The short-tailed field vole is both widespread and common and is listed as being of "Least Concern" by the IUCN.

<span class="mw-page-title-main">Venomous mammal</span> Venom-producing animals of the class Mammalia

Venomous mammals are animals of the class Mammalia that produce venom, which they use to kill or disable prey, to defend themselves from predators or conspecifics or in agonistic encounters. Mammalian venoms form a heterogeneous group with different compositions and modes of action, from four orders of mammals: Eulipotyphla, Monotremata, Primates, and Chiroptera. To explain the rarity of venom delivery in Mammalia, Mark Dufton of the University of Strathclyde has suggested that modern mammalian predators do not need venom because they are able to kill quickly with their teeth or claws, whereas venom, no matter how sophisticated, requires time to disable prey.

Soricidin is a paralytic oligopeptide found in the venomous saliva of the northern short-tailed shrew ; in the wild, shrews use it to paralyze their prey. Its name is a reference to "Soricidae", the family to which shrews belong.

References

  1. Hutterer, R. (2005). Wilson, D.E.; Reeder, D.M. (eds.). Mammal Species of the World: A Taxonomic and Geographic Reference (3rd ed.). Johns Hopkins University Press. p. 269. ISBN   978-0-8018-8221-0. OCLC   62265494.
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  6. 1 2 Brant, Sara V.; Orti, Guillermo (2003), "Phylogeography of the Northern short-tailed shrew, Blarina brevicauda (Insectivora: Soricidae): past fragmentation and postglacial recolonization", Molecular Ecology, 12 (6): 1435–1449, doi:10.1046/j.1365-294x.2003.01789.x, PMID   12755873, S2CID   8438791, archived from the original on 2013-01-05
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  10. Robinson, Denise E.; Brodie, Edmund D. Jr. (1982), "Food Hoarding Behavior in the Short-tailed Shrew Blarina brevicauda", American Midland Naturalist, 108 (2): 369–375, doi:10.2307/2425498, JSTOR   2425498
  11. Kita, Masaki; Nakamura, Yasuo; Ohdachi, Satoshi D.; Oba, Yuichi; Yoshikuni, Michiyasu; Kido, Hiroshi; Uemura, Daisuke (2004), "Blarina toxin, a mammalian lethal venom from the short-tailed shrew Blarina brevicauda: Isolation and characterization", PNAS, 101 (20): 7542–7547, Bibcode:2004PNAS..101.7542K, doi: 10.1073/pnas.0402517101 , PMC   419642 , PMID   15136743
  12. Aminetzach et al. 2009
  13. 1 2 Martin, Irwin G. (1983), "Daily Activity of Short-tailed Shrews (Blarina brevicauda) in Simulated Natural Conditions", American Midland Naturalist, 109 (1): 136–144, doi:10.2307/2425523, JSTOR   2425523
  14. 1 2 Merritt, Joseph F. (1986), "Winter Survival Adaptations of the Short-tailed Shrew (Blarina brevicauda) in an Appalachian Montane Forest", Journal of Mammalogy, 67 (3): 450–464, doi:10.2307/1381276, JSTOR   1381276
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