biology

Northern short-tailed shrew

Northern short-tailed shrew is a biology topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Northern short-tailed shrew rather than just read about it. In short: 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 like broadleaved and pine forests among shrubs and hedges as well as grassy river banks.

Key takeaways

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Reference excerpt

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 like broadleaved and pine forests among shrubs and hedges as well as grassy river banks. 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".

Taxonomy B. brevicauda is a red-toothed shrew, 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 (B. carolinensis). 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. The two groups of subspecies are thought to have been kept isolated from each other by Pleistocene glaciers.

Description

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). The species 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 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. 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.

Distribution

Fossil record Most records of B. brevicauda are from the Pleistocene, though one record from the late Pliocene (Blancan land mammal age) is tentatively attributed to this species. 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. The B. b. brevicauda subspecies appeared later.

Range This shrew is found throughout central and eastern North America, from southern Saskatchewan to Atlantic Canada and south to northern Arkansas and Georgia. It is probably the most common shrew in the Great Lakes region. Population densities usually range from five to 30 shrews per hectare (two to 12 per acre), but rarely exceed 200/ha (80/ac). The typical home range of a shrew is 2.5 ha, 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, deciduous and coniferous forests, and household gardens, though the preferred habitats are those which are moist with leaf litter or thick plant cover. Burned-over forests are not quickly recolonized by B. brevicauda, and shrews quickly depart clear-cuts.

Diet This shrew consumes up to three times its weight in food each day. It eats small quantities of subterranean fungi and seeds, though it is mostly carnivorous. It prefers insects (such as beetles), earthworms, voles, snails, and other shrews for the bulk of its diet, though salamanders, frogs, snakes, birds, and mice are also eaten. This shrew consumes vertebrates 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 it caches 87% of the prey it catches, while 9% is eaten immediately and 4% is left where it was killed.

Toxin The saliva 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 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. 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.

Epidemiology Northern short-tailed shrews in Alabama have been identified as carriers of the newly-discovered Camp Hill virus that is not known to cause disease but which is distantly related to Nipah virus. "Researchers at an Auburn University lab collected" the shrew, according to a news report, "that was found with a new species of henipavirus named after the Alabama town where the specimen came from". The research letter appeared in a scholarly publication, but was not peer reviewed.

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, but the shrew compensates by using echolocation and a fine sense of touch.

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Illustrations

Worked examples

Example 1 — a first encounter with Northern short-tailed shrew

Start with the simplest possible case. Write down what Northern short-tailed shrew claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Northern short-tailed shrew before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Northern short-tailed shrew ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Northern short-tailed shrew

In research: Northern short-tailed shrew appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Northern short-tailed shrew in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Northern short-tailed shrew is common in secondary-school and first-year university syllabi. It links to neighbouring topics Animals that use echolocation, Blarina, IUCN Red List least concern species, so understanding it makes those chapters shorter.
In everyday life: Look for Northern short-tailed shrew outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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Frequently asked questions

What is Northern short-tailed shrew in simple terms?

Why does Northern short-tailed shrew matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Northern short-tailed shrew?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

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