Copyright 1999. The Smithsonian Book of North American Mammals,
edited by Don E. Wilson and Sue Ruff. All rights reserved. http://www.discoverlife.org/nh/tx/Vertebrata/Mammalia/Soricidae/Cryptotis/parva/
Habitat
The least shrew primarily inhabits an area from southeastern Canada down through the southeastern United States. Additionally, the least shrew can be found in some parts of Central America, especially Mexico, and also spans across the midwestern United States. The least shrew is by no means a rare animal and is quite abundant in certain regions such as the marshes along the South Atlantic coast. Cryptotis parva is the only species of the genus Soricidae that is found in areas north of Mexico.
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Copyright 1999. The Smithsonian Book of North American Mammals, |
The least shrew lives predominantly in grassy fields populated by dense stands of weeds and other brush, but it can also be found in marshy or wooded areas occasionally. Researchers largely agree that least shrews are most commonly found in pastures, vacant lots, and fields. All of these areas are characterized by the abundance of dense grasses in which the least shrew can hide and dig burrows. Dense grass cover seems to be an important component of the least shrew habitat (Davis and Joeris 1945). Davis and Joeris also found that the soil type seems to have little effect on where the least shrew makes its home, but that only dense grass cover is needed for the least shrew to set up shop. The least shrew has been described as a habitat specialist, specializing in open grassy areas and in areas along streams. Most research has concluded that the least shrew usually makes its home in old fields and that it does not live in forested areas very often. However, one particular researcher did discover a significant number of least shrews in a forest in Florida, which demonstrates that least shrews can live in cool, moist forests under certain circumstances (Kale 1972).
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Image courtesy of Herbert W. Kale II from "A High Concentration of Cryptotis parva in a Forest in Florida." (Journal of Mammalogy) Permission pending. |
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Nests and Burrows
Many researchers have discovered nests containing large numbers of least shrews living colonially in one nest. A nest was found containing 31 individuals in eastern Texas (McCarley 1959). This number is the largest quantity of this species reported to be living in a single nest together to date. When McCarley discovered the shrew nest, he simply prodded it to flush the shrews out and then counted the number of shrews which came running out. The least shrew's group living style starkly contrasts with the largely solitary social behavior of most other species of shrews. Least shrews also construct burrows and build tiny runways through the soil by digging with their feet. Evidence of cooperative digging among the least shrew while creating these tunnels has been documented. Burrows typically go eight to ten inches below the surface and almost always culminate in a nest (Davis and Joeris 1945). The least shrew will use tunnels made by other small mammals as well. The nests are located in hidden areas and are composed mostly of dried grasses. The nests are roughly equivalent to a human fist in size and all adults help with building the nest. Least shrews are also known to keep their nests very clean and often groom and wash themselves thoroughly.
In one study, researchers created an artificial rain on boxes containing least shrew nests (Esher and Wolfe 1981). They discovered that the shrews living in underground burrows got soaked and came out and died at the surface of the burrow. Thus, it may be that rainstorms in the natural environment which lead to flooding of the burrow can produce a notable degree of death in a least shrew population. However, when the least shrews inhabited nests on the surface which they constructed themselves, they survived the artifical rainstorms and the subsequent flooding.
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Photo courtesy of Eric and David Hosking/Corbis http://www.britannica.com/eb/art/print?id=89360&articleTypeId=0 |
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Predators
Owls are the main predators of the least shrew. Many researchers have noted an abundance of least shrew remains in owl pellets, especially in those of barn owls. It is rare that an owl pellet will not contain at least some least shrew remains and in one study, up to 41% of the prey items in various owl pellets were of least shrew origin (Davis 1938). Other predators of least shrews include cats, hawks, raccoons, snakes, foxes, and weasels. Least shrews avoid predators not by running away, but by finding shelter or hiding in dense grass stands. Although owls are able to catch and consume least shrews on a regular basis, it is quite difficult to trap the least shrew to conduct captivity studies and learn more about this species.
This website was completed in partial fulfillment of the requirements for Biology 323, Animal Behavior, at Davidson College in the Spring Semester 2008.
© Copyright 2008 Department of Biology, Davidson College, Davidson, NC 28035
Please send any comments, questions, or suggestions regarding this website to Nate Geigle or Professor Verna Case.