Least shrews have thick, short hair that is dark or reddish brown on top in winter. In summer, their fur turns grayish brown. Their tail is dark brown on top, lighter on the bottom, and only 12 to 26 mm long. Their whole bodies are 70 to 92 mm long and weigh 3 to 6 g. Males and females both have scent glands on their flanks, and females have an extra set in front of their ears. (Choate, et al., 1994; Laerm, et al., 2007; Linzey, 1998; Schwartz and Schwartz, 1981; Whitaker, 1974; White and Seymour, 2003)
Least shrews live mostly in the eastern United States. They are found up the east coast from Florida to New York and as far west as Texas and South Dakota. They also live in Central America, and from northern Mexico to Costa Rica and Panama. (Laerm, et al., 2007; Linzey, 1998)
Least shrews are most commonly found in open fields with tall grasses and places that have fallen trees and brush for protection. They also live near saltwater marshes along the Atlantic Coast. Some are found in the forests of Florida, where they use small plants in the forest for cover. They live at elevations up to 2,100 m. (Choate, et al., 1994; Hafner and Shuster, 1996; Hamilton, 1944; Kale, 1972; Laerm, et al., 2007; Linzey, 1998; Schwartz and Schwartz, 1981)
Females stop releasing their normal pheromone chemicals right before they are ready to mate. If a female does not want to mate with a particular male, she can get aggressive, making loud noises and arching her back. Females may mate with multiple males in a season. If more than one male is present, the more aggressive ones mate first. (Choate, et al., 1994; Kivett and Mock, 1980; Schwartz and Schwartz, 1981; Whitaker, 1974)
Least shrews can reproduce several times during the mating season, which lasts all the way from February to November. Babies grow inside the mother for 21 to 23 days. Females give birth to 2 to 7 young, but 5 on average. Newborns weigh just .34 g, and drink their mother's milk for the first 23 days. Females are able to mate after 40 days, and males after 43 days. (Choate, et al., 1994; Hamilton, 1944; Kivett and Mock, 1980; Schwartz and Schwartz, 1981; Whitaker, 1974)
Female least shrews care for their young by nursing them for 20 to 23 days. Most adults keep them from getting lost by carrying them around in their mouths. Mothers show panic if separated from their young and, when reunited, gather all of their young together. (Kivett and Mock, 1980; Schwartz and Schwartz, 1981; Whitaker, 1974)
Least shrews are very social compared to other shrews. They live in large groups called colonies, which can have up to 31 least shrews living together. Their colonies are groups of tunnels that are 24.5 to 150 cm long. They work together to dig the tunnels. Occasionally, they take over tunnels dug out by other small mammals. Least shrews build their nests within the tunnels. Their small round nests are made from plant parts like fallen leaves and grasses. Nests have two or more openings into the tunnel system. (Choate, et al., 1994; Linzey, 1998; Schwartz and Schwartz, 1981)
Least shrews are active about 11 hours each day, during both the day and night. They are most active at night and least active during very hot and cold months. They spend most of their time staying hidden from predators and hunting. If they hunt down a larger animal, they share food. If food is very scarce, they might eat each other. (Choate, et al., 1994; Linzey, 1998; Schwartz and Schwartz, 1981)
Least shrews mostly look for food in an area of about 0.20 hectares. They defend their nests but not their whole home range. (Choate, et al., 1994)
Least shrews make lots of noises. They make make chirps and clicks, some of which humans can't hear. They also use ultrasonic sounds to explore tunnels, which is a kind of echolocation. Males and females also communicate through scent. Males announce their presence to females through their scent. Females only produce a scent when they are not ready to mate or are pregnant. (Schwartz and Schwartz, 1981)
Least shrews eat a ton of food: 60 to 100% of their own body weight every day. They eat mostly insects, specifically insect larva and centipedes. They can also eat snails, spiders, and crickets. They eat little bits of fungi and other green plants. Least shrews paralyze their prey by attacking their joints. (Choate, et al., 1994; Laerm, et al., 2007; Schwartz and Schwartz, 1981)
Owls are the most common predators of least shrews. Other common predators are rough-legged hawks, foxes, and snakes. House cats and spotted skunks also eat them. If food is scarce, least shrews may also eat each other. Their only defense against predators is camouflage. (Choate, et al., 1994; Linzey, 1998)
When least shrews burrow, they allow air and nutrients to flow through the soil. Least shrews can eat up to 100% of their body weight in a day and may therefore help control populations of insects. They are also eaten by a variety of predators, such as snakes and owls. Least shrews are known to host various fleas and mites such as Orycteroxenus soricis and Androlaelaps fahrenholzi. (Schwartz and Schwartz, 1981; Whitaker, 1974)
There are no known negative impacts of least shrews on humans.
Least shrews eat lots of insects, and may help protect crops from harmful insects. They also benefit farmers by loosening up soil when they burrow through it. (Schwartz and Schwartz, 1981)
The state of Michigan lists least shrews as threatened, though they have strong numbers in other states. Currently, scientists don't know why populations are declining in Michigan. (Laerm, et al., 2007)
Adam Ohl (author), Radford University, Catherine Kent (author), Special Projects, Karen Powers (editor), Radford University, Gail McCormick (editor), Animal Diversity Web Staff.
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