Diet
The least shrew is primarily an insectivore, feeding on centipedes, beetle larvae, crickets, grasshoppers, and other insects. Cryptotis parva is a solitary forager and does not engage in group hunting, presumably because with such a voracious appetite and high metabolism, sharing a prey item with others is simply not feasible. Due to their small body size and high metabolism, they spend a large majority of their time actively foraging. They do eat some vegetation on rare occassions and have been known to consume frogs and lizards in captivity. Least shrews are also known to search beehives for larvae and pupae and consequently are often called “bee shrews” (Bonta 1997, Evermann and Butler 1984). After consuming all the bee larvae, they sometimes then will make their nest out of the empty beehive.
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© Copyright The Smithsonian Book of North American Mammals, edited by Don E. Wilson & Sue Ruff, 1999. All rights reserved. http://www.discoverlife.org/nh/tx/Vertebrata/Mammalia/Soricidae/Cryptotis/parva/ |
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The least shrew attacks by rushing at its prey and then biting the prey numerous times to immobilize it. Smaller prey items do not need to be immobilized as much and thus least shrews readily chomp down small insects, but shrews do have a reputation for attacking prey species that are larger than their own body size. One researcher asserts that sight and smell in the least shrew are both subpar and that the tactile sense is the most important for finding prey items (Hamilton 1944). The least shrew uses its vibrissae and sensitive snout for finding insects and other food. It pokes around in loose soil and leaf litter, making use of its vibrissae in this process of detection. However, other authors believe that the least shrew relies mostly on smell in the process of prey detection and tracking (Moore 1943). Contrasting research results have demonstrated that the least shrew has a keen sense of smell and possesses large olfactory bulbs in the brain.
Video: Shrew attacks and eats scorpion
Feeding Behavior
Research results have demonstrated that fighting does not usually occur between least shrews, even when they desire the same piece of food. However, fights over food do occur rarely among the least shrews. Moreover, the presence of partial cannibalistic behavior among the least shrews has been observed. A shrew that had died in captivity was gnawed on and then eaten by the other least shrews in the cage. Researchers also discovered that in one instance when two shrews were caught together in the same trap, one shrew had been partially eaten by the other shrew. In captivity studies, four shrews in one cage only fought when one piece of food was offered among all four (Davis and Joeris 1945). Through observing least shrews in captivity, Davis and Joeris also noted that the least shrews slept and ate together most of the time. They noted that in several instances, a smaller shrew would carry food into the nest for a larger shrew. This only occurred when food was in abundance, and did not occur when food was scarce. These researchers also note that it is very likely that these shrews act similarly in nature as in captivity.
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Photo courtesy of Bob Gress and gpnc.org. Accessed March 25, 2008. http://www.gpnc.org/shrewl.htm |
Some cutting-edge research has also suggested that mutant shrews sometimes prey on humans? The Killer Shrews Trailer
Hoarding Behavior
Least shrews do in fact store extra food in their burrows for later use. When a surplus of food has been presented in captivity studies, the shrews immediately kill the prey items and fill their bellies to capacity. The prey items that are not consumed are cached in a corner of the cage. One least shrew hoarded 12 black crickets in a corner of the cage in about 5 minutes time (Davis and Joeris 1945). In another study, researchers closely examined the hoarding behavior of male and female least shrews (Formanowicz et. al 1989). The authors first noted that Cryptotis parva is primarily a larder hoarder. Larder hoarders hoard food by creating a larder and concentrating food resources at a specific, protected, and defendable location (Formanowicz et. al 1989). Larger prey (crickets) were hoarded nearer to the nest, while smaller prey (mealworms) were hoarded farther away from the nest.
Why Hoard?
Storing the larger, higher value prey near the nest lessens the likelihood of its loss to other foragers or scavengers. Least shrews also preferred to hoard the crickets over the mealworms, indicating a significant hoarding preference for larger insects. Futhermore, female least shrews hoarded more than the males. The authors of the study hypothesize that this is the case because females require much more energy for parental care and reproduction than do the males. Female least shrews also need to have a higher foraging efficiency because of the higher energetic demands of pregnancy. For a pregnant female or for a female nursing her young, a larder full of hoarded food drastically decreases the amount of foraging time needed and thus decreases the amount of time the mother is away from her young.
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.