The Inyo shrew (''Sorex tenellus'') is a species of

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 diffe ...

found in the western

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., federal district, five ma ...

. Not much is known about its behavioral and reproductive habits. It is small, very similar in appearance to the related dwarf shrew (''Sorex nanus''), but smaller and paler. It can be found in many different habitats, from rocky, mountainous regions to wetlands and riparian areas. While barely studied, their population is believed to be stable and not under any threat.

Taxonomy

''Sorex tenellus'' was first described by

Clinton Hart Merriam Clinton Hart Merriam (December 5, 1855 – March 19, 1942) was an American zoologist, mammalogist, ornithologist, entomologist, ecologist, ethnographer, geographer, naturalist and physician. He was commonly known as the 'father of mammalogy', a ...

in 1895. He identified two subspecies, one of which, ''Sorex tenellus nanus'', has since been elevated to species status as '' Sorex nanus''. He studied three specimens of the

nominate subspecies In biological classification, subspecies is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics ( morphology), but that can successfully interbreed. Not all spec ...

and four of ''S. t. nanus''. The type locality, Lone Pine Creek, is located in

Inyo County, California Inyo County () is a county in the eastern central part of the U.S. state of California, located between the Sierra Nevada and the state of Nevada. In the 2020 census, the population was 19,016. The county seat is Independence. Inyo County i ...

. In 1902, from specimens collected the previous summer, he identified two new subspecies — ''S. t. lyelli'' and ''S. t. myops''. The former is now given species status as '' Sorex lyelli'', while the latter temporarily received the same from Hartley Harrad Thompson Jackson in 1928. Later, in 1941, a study published in the

Journal of Mammalogy The ''Journal of Mammalogy'' is a bimonthly peer-reviewed scientific journal published by Oxford University Press on behalf of the American Society of Mammalogists. Both the society and the journal were established in 1919. The journal covers rese ...

concluded ''Sorex myops'' to simply be a synonym of ''S. tenellus''. It is sometimes referred to as the Great Basin dwarf shrew to distinguish it from ''Sorex tellenus'', the dwarf shrew or Rocky Mountain dwarf shrew.

Description

The Inyo shrew is small and pale in color. Its upper regions are a light ash gray, while its lower regions and feet are white. The tail is bicolored, with the top darker than the white underside. Its

skull The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, t ...

is small, narrow, and extremely flat. The

braincase In human anatomy, the neurocranium, also known as the braincase, brainpan, or brain-pan is the upper and back part of the skull, which forms a protective case around the brain. In the human skull, the neurocranium includes the calvaria or skul ...

is depressed to the rostrum and the

palate The palate () is the roof of the mouth in humans and other mammals. It separates the oral cavity from the nasal cavity. A similar structure is found in crocodilians, but in most other tetrapods, the oral and nasal cavities are not truly s ...

is slender. There is no major

sexual dimorphism Sexual dimorphism is the condition where the sexes of the same animal and/or plant species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction. The condition occurs in most an ...

. In size, it ranges from long, with a tail length of and a weight of . Compared to the dwarf shrew (''Serox nanus''), with which it was once considered

conspecific Biological specificity is the tendency of a characteristic such as a behavior or a biochemical variation to occur in a particular species. Biochemist Linus Pauling stated that "Biological specificity is the set of characteristics of living organ ...

, ''S. tenellus'' is slightly bigger, with a longer tail. It is also paler and grayer. Like other small shrews, it molts biannually — to its summer coat in mid-to-late July and its winter coat most likely in October. Due to its intermediate size and body mass between the larger dwarf shrew and smaller ornate shrew, as well as the potential that their ranges overlap (although this has not been observed so far), it is possible that the three form a single species.

Distribution and habitat

The Inyo shrew lives exclusively in the

. According to 2016 data by the

International Union for the Conservation of Nature The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natu ...

(IUCN), they are found only in the states

California California is a state in the Western United States, located along the Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the most populous U.S. state and the 3rd largest by area. It is also the ...

and

Nevada Nevada ( ; ) is a state in the Western region of the United States. It is bordered by Oregon to the northwest, Idaho to the northeast, California to the west, Arizona to the southeast, and Utah to the east. Nevada is the 7th-most extensive, ...

. However, a specimen was recorded in 2014 in Granite Creek Canyon, Deep Creek Range, Juab County,

Utah Utah ( , ) is a state in the Mountain West subregion of the Western United States. Utah is a landlocked U.S. state bordered to its east by Colorado, to its northeast by Wyoming, to its north by Idaho, to its south by Arizona, and to its ...

, the easternmost discovery of a ''Serox tenellus'' individual at that time, as well as the first in Utah. It dwells in a variety of habitats, including

riparian zones A riparian zone or riparian area is the interface between land and a river or stream. Riparian is also the proper nomenclature for one of the terrestrial biomes of the Earth. Plant habitats and communities along the river margins and banks ...

, canyon bottoms, rocky and mountainous areas, and communities of

red fir ''Abies magnifica'', the red fir or silvertip fir, is a western North American fir, native to the mountains of southwest Oregon and California in the United States. It is a high-elevation tree, typically occurring at elevation, though only rare ...

s. They may have a relatively high tolerance for drier environments. They are usually found at altitudes above . While a more marginal habitat, they can also inhabit

wetlands A wetland is a distinct ecosystem that is flooded or saturated by water, either permanently (for years or decades) or seasonally (for weeks or months). Flooding results in oxygen-free ( anoxic) processes prevailing, especially in the soils. The ...

. The species has been found living in

sympatry In biology, two related species or populations are considered sympatric when they exist in the same geographic area and thus frequently encounter one another. An initially interbreeding population that splits into two or more distinct species s ...

with Preble's shrew (''Sorex preblei'') at California's

Lassen Volcanic National Park Lassen Volcanic National Park is an American national park in northeastern California. The dominant feature of the park is Lassen Peak, the largest plug dome volcano in the world and the southernmost volcano in the Cascade Range. Lassen Vol ...

Behavior and ecology

Essentially nothing is known about the Inyo shrew's ecology, behavior, or reproduction, due to how little study it has received. It mainly consumes

insects Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (head, thorax and abdomen), three pairs ...

(possibly wind-borne insect bodies left at high altitudes), as well as other small

invertebrates Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordate ...

(such as

worm Worms are many different distantly related bilateral animals that typically have a long cylindrical tube-like body, no limbs, and no eyes (though not always). Worms vary in size from microscopic to over in length for marine polychaete worm ...

mollusks Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is esti ...

, and

centipedes Centipedes (from New Latin , "hundred", and Latin , "foot") are predatory arthropods belonging to the class Chilopoda (Ancient Greek , ''kheilos'', lip, and New Latin suffix , "foot", describing the forcipules) of the subphylum Myriapoda, an ...

). It remains active the entire year.

Conservation

There are most likely well over 10,000 individuals alive today, and their population is stable. The IUCN has identified no threats and declared there to be no need to introduce new protection measures. It is found in multiple

protected areas Protected areas or conservation areas are locations which receive protection because of their recognized natural, ecological or cultural values. There are several kinds of protected areas, which vary by level of protection depending on the ena ...

References

{{Taxonbar, from=Q548651 Sorex Endemic fauna of California Endemic fauna of Nevada Fauna of the Great Basin Fauna of the Sierra Nevada (United States) Mammals of the United States Natural history of Inyo County, California Great Basin National Park Lassen Volcanic National Park Least concern biota of the United States Taxonomy articles created by Polbot Mammals described in 1895