MATERNAL BEHAVIOR IN RAT - AN INVESTIGATION AND QUANTIFICATION OF NEST BUILDING

A technique has been developed to quantify nest building in rats. Small wooden dowels are provided as nest material. Rats shred the dowels, and the degree of nest building is determined by the amount shredded daily. Pregnant females show a marked increase in dowel shredding at or just prior to the time of parturition; shredding falls precipitously after parturition. Males and nonpregnant females show no such pattern over an equivalent period of time; their dowel shredding, in fact, decreases over time. A series of experiments were carried out involving hormone manipulations of pregnant and nonpregnant females. The only significant finding was that progesterone reduced the percentage of females which shredded dowels and also delayed the time of onset of this behavior. When nonpregnant females and males were exposed to cool ambient temperatures, dowel shredding increased markedly. On the other hand, exposing females to a warm temperature blocked dowel shredding behavior. Some similarities and differences between these findings and findings for the rabbit and mouse are discussed.