Behavior
Photo by Thomas C. Merigan
House Construction
N. macrotis builds conical, highly structured houses from sticks, bark, plant cuttings, and miscellaneous objects (Vreeland and Tietje, 2004; Lindsdale and Tevis, 1951; English, 1923). The amount of amassed debris may be so large that the tree trunk supporting the structure is completely obscured (Carraway and Vert, 1991). Openings are commonly found where trees protrude (Carraway and Verts, 1991). These openings occur throughout different heights of the house and allow air and sunlight to penetrate the house’s interior (Carraway and Vert, 1991). Woodrats prefer areas with lots of cover (Vreeland and Tietje, 2004) and will spend the majority of their time in houses that have 75-100% cover (Cranford, 1977). Woodrats frequently incorporate bay leaves into their houses and it is thought to reduce the amount of parasites present within the house (Hemmes et al, 2002).
House Characteristics
Houses are 2-8 feet in height and diameter and conical in shape (English, 1923). Large houses are divided in to as many as five compartments (English, 1923). These compartments serve as nursery, living room, storage chambers, and a place to pile dung (Vestal, 1938; English, 1923). All compartments are connected by a series of runways, making communication easy (English, 1923). Each compartment has an exit (English, 1923). With the exception of the dung chamber, all other compartments are very clean and lined with softer materials (English, 1923). Various openings occur at all heights because of protruding tree limbs (English, 1923).
House Maintenance
Houses are often occupied by several successive generations of N. macrotis (English, 1923). Each successive generation adds new material to each nest and this explains why some nests become so large (English, 1923). When houses fall into disrepair, they are often no longer used (Wallen, 1982) and fully decompose. Woodrats actively engage in housekeeping. Woodrats take care not urinate within their house and will remove excrement when the chamber that holds it becomes too full (Vestal, 1938; English, 1923).
Conspecific Interactions
Female-female encounters are non-agonistic (Wallen, 1982). If the females are familiars, they will usually ignore each other and self-groom (Wallen, 1982). If the females are strangers, the dominant female will make contact with the less dominant female (Wallen, 1982). Male-female interactions can have three outcomes that are male-specific. In the first outcome, the female will cross over to the male and be affiliative (Wallen, 1982). In the second outcome, the male will cross to the female and an agonistic encounter will ensue (Wallen, 1982). In the third outcome, the male and female will ignore each other (Wallen, 1982). The outcome from a male-female interaction depends on the personality of the male; less aggressive males will have the first or third outcome whereas more aggressive males will have an agonistic encounter (Wallen, 1982). In male-male interactions, stranger males do not interact (Wallen, 1982). Interactions between familiar males depend on whether the males are aggressive or not (Wallen, 1982). It is not clear what kind of diminance structure, if any, is in place, but there is social polarization between more aggressive and less aggressive individuals of both sexes (Wallen, 1982). Males visit more whereas females are visited more, but woodrast avoid visiting each other at their occupied residences (Wallen, 1982).
Tail Rattling
A common noise heard around woodrat houses are tail rattles. The tail rattle is produced by the rapid vibration of the distal third of the tail against a substrate (Vestal, 1938). Each rattle lasts approximately three seconds and will be repeated at ten-second intervals (Vestal, 1938). There are two theories about the reason woodrats exhibit tail rattling behavior. The first theory is that tail rattling is a response to a disturbance (Hamm et al, 2002). Whether the woodrats detect a disturbance through olfaction, auditory perception, vision, or some combination of the three is unclear (Vestral, 1938). Both sexes and juveniles exhibit tail rattling behavior (Hamm et al, 2002).
This website was completed in partial fulfillment of the requirements for Biology 323, Animal Behavior, at Davidson College in the spring semester 2008
Please direct questions, comments, or suggestions regarding this site to Carolyn Kiss or Dr. Verna Case