Social Relationships

Compared to most species of shrews, least shrews are quite social. Nests with many individuals living together communally have been documented on many occasions. Most species of shrews are territorial and solitary. However, a noted lack of territoriality, group living, and cooperation characterize the least shrew. Researchers observing least shrews in captivity have found that the shrews spent a lot of time together and sleep and eat together. Kivett and Mock agree with other researchers that compared to other shrews, the least shrews’ social behavior can be described as "amicable" (Kivett and Mock 1980). In times of food excess, a smaller shrew sometimes will bring food to a larger shrew (Davis and Joeris 1945). Although this behavior may hint at a latent dominance hierarchy within the least shrews, this only occurred when food was in abundance, and did not occur when food was scarce.Watching the behavior of these shrews in captivity also has enabled researchers to observe least shrews digging tunnels in the glass vivarium in which they were housed (Davis and Joeris 1945). Two shrews cooperated in digging a burrow in which one did most of the digging, while the other removed the loosened earth and packed down the walls of the tunnel. The two shrews worked at this project together continuously for almost two hours.



	Cryptotis parva in a nest box. Photo courtesy of Danielle Garneau, Colgate University. http://danielle.garneau.googlepages.com/teachingexperiences-colgate

High-pitched sounds and echolocation also may be involved in their social behavior and in the least shrew communication system. Fighting among least shrews is rare, contrasting with the behavior of other shrew species, which are usually aggressive and often fight among each other. While analyzing the behavior of least shrews in captivity, one researcher observed that no fighting took place between least shrews and that they lived in close proximity without fighting (Springer 1937). In captivity, one corner of the cage is used as colonial nest, while the other corner of the cage is used for defecation and urination (Conaway 1958). The least shrews maintain a very organized and cleanly nest space.

The least shrew is a solitary forager and its prey does not require group hunting. Thus no dominance hierarchy is needed in order to organize and control group hunting. Territoriality and dominance may be able to be eschewed in this species due to the energy-saving practice of communal nesting. Due to this practice, less food resources are needed to enable the least shrew to survive. A solid and stringent dominance hierarchy is also not needed for breeding purposes, as the least shrew exhibits overlap promiscuity. However, there is some data to suggest that the least shrew males may set up a very short-lived dominance hierarchy when breeding in which social status plays a role (Kivett and Mock 1980). For a more in depth explanation of this phenomenom, see the mating behavior section of the website. So, the least shrew is not territorial, does not exhibit a dominance hierarchy, and is suprisingly social and cooperative in its behavior for a shrew. Kin-selection and altruism have not yet been recorded or researched extensively in the least shrew, and studies looking into these areas would be informative. Kin selection is most likely to occur in species that produce numerous offspring at the nest and in species which live in close proximity to one another. The least shrews do live in close proximity to each other within the communal nest, so kin selection may be a possibilty when looking at this criterion. However, with an average litter size of five, the size of the litter is not quite large enough to make kin selection feasible among the least shrews.

A large degree of information regarding the least shrew comes from observing the behavior of captured shrews or the social interactions and behavior of shrews raised in captivity. After observing the least shrew extensively in captivity, one researcher came to the conclusion that “this species is remarkably social in behavior” (Conaway 1958). In the community cages, Conaway did not observe any agonistic or aggressive behavior whatsoever among the shrews. However, when a new shrew was introduced, an immediate violent conflict did ensue on rare occassions. This demonstrates that least shrews are not entirely always amicable and non-violent toward each other. But on most occassions when a new shrew was introduced to the cage, the new shrew was incorporated into the existing colony with little trouble, indicating the high degree of amicability and sociability within the least shrew (Conaway 1958). Furthermore, first-hand reports and field observations have discovered that they act similarly in nature and are just as social in the wild as they are in captivity.

References Page

Least Shrew Home Page

This website was completed in partial fulfillment of the requirements for Biology 323, Animal Behavior, at Davidson College in the Spring Semester 2008.

Please send any comments, questions, or suggestions regarding this website to Nate Geigle or Professor Verna Case.