Graduate Program

Biological Sciences

Degree Name

Master of Science (MS)

Semester of Degree Completion

2007

Thesis Director

Zhiwei Liu

Thesis Committee Member

Gary Fritz

Thesis Committee Member

James Novak

Thesis Committee Member

Emily Latch

Abstract

The North American beaver, Castor canadensis, is an important wildlife species for a variety of reasons. As a furbearer, it provides income and recreation to trappers throughout the state. As a wetland engineer, it helps maintain functioning ecosystems (Naiman et al. 1986, McKinstry and Anderson 2002). Finally, the beaver serves as a model organism for studies of mating and kinship, as it has beed reported to be almost exclusively monogamous (Sun 2003).

Monogamy in mammals is generally restricted to the primates, canids, and rodents, and is defined as a mating system in which a pair remains together for at least one breeding season (Kleiman 1977, Reichard 2003). Beavers most often are found living in discrete colonies composed of a mated adult pair and their offspring from the previous 2­ 3 breeding seasons (Bradt 1938, Novak 1977, Busher et al. 1983, Svendsen et al. 1980, Sun 2003). Svendsen (1989) has reported that beaver pairs remained together for an average of2.5 years. Most pairs consisted of an older beaver paired with a younger one, and termination of the bond occurred upon the death of the older mate. The duration of pair bonds is highly variable among monogamous taxa. For example, the Malagasy giant jumping rat (Hypogeomys antimena) forms long-term associations that last until the death of a partner (Sommer 2003). The California mouse (Peromyscus califomicus) and the prairie vole (Microtus ochrogaster) also form long-term pair-bonds and, like beavers, exhibit many behavioral characteristics associated with a monogamous mating system (Lonstein and De Vries 2000). In contrast, some avian species fonn pairs that last only one breeding season (Birkhead and Moller 1995).

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