Abstract
Female mice construct nests of two general types depending upon the reproductive status of the animal. During pregnancy female mice build large, enclosed nests with multiple tunnels. This has been called the brood nest as opposed to the sleeping nest of the nonpregnant mice (2, 3). Also pseudopregnant mice displayed maternal nest building behavior (1). Their nests were smaller but qualitatively identical to those constructed by pregnant animals. Progesterone apparently is responsible for the maternal nest building in female mice, since the administration of progesterone can induce construction of brood nest in nonpregnant females (2, 4, 5).
The present study was planned to clarify whether high levels of progesterone are necessary for appearance of the maternal nest building behavior by measuring simultaneously plasma progesterone levels and the amount of nest built in pseudopregnant and pregnant mice.
