Northern short-tailed shrew

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Northern short-tailed shrew[1]

Least Concern  (IUCN 3.1)[2]
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Eulipotyphla
Family: Soricidae
Genus: Blarina
Species:
B. brevicauda
Binomial name
Blarina brevicauda
(Say, 1823)

The northern short-tailed shrew (Blarina brevicauda) is the largest

venomous mammals. The specific epithet, brevicauda, is a combination of the Latin brevis and cauda, meaning "short tail".[3]

Taxonomy

B. brevicauda is a

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

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).

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

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,

clear-cuts.[3]

Diet

This shrew consumes up to three times its weight in food each day.

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

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;

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]

References

  1. OCLC 62265494
    .
  2. ^
    doi:10.2305/IUCN.UK.2016-3.RLTS.T41451A22292945.en
    . Retrieved 11 March 2022.
  3. ^ a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac ad ae af ag ah ai aj ak "Mammalian Species Accounts: Northern Short-tailed Shrew (Blarina brevicauda)" (PDF). Retrieved 2024-03-12. Includes a range map.
  4. ^ a b c d e f g h i j "Animal Diversity Web: Blarina brevicauda". Retrieved 2008-11-23.
  5. ^
    ISBN 978-0-472-06497-7
    .
  6. ^
    S2CID 8438791, archived from the original
    on 2013-01-05
  7. ^ "The Paleobiology Database - Blarina brevicauda". Retrieved 2008-11-23.
  8. ^ "The Paleobiology Database - Collection 19930". Retrieved 2008-11-23.
  9. S2CID 85875955
    .
  10. JSTOR 2425498
  11. PMID 15136743
  12. ^ Aminetzach et al. 2009
  13. ^
    JSTOR 2425523
  14. ^
    JSTOR 1381276
  15. ^
    JSTOR 2424868
  16. JSTOR 2425153
  17. ^ "The Naming of the Shrew". 11 December 2017.
  • Aminetzach, Yael T.; Srouji, John R.; Kong, Chung Yin & Hoekstra, Hopi E. (2009): Convergent Evolution of Novel Protein Function in Shrew and Lizard Venom. Current Biology
    doi:10.1016/j.cub.2009.09.022
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