A multivariate assessment of spontaneous locomotor activity in the Mongolian gerbil (Meriones unguiculatus): influences of age and sex.

A multivariate assessment of the spontaneous locomotor activity of male and female Mongolian gerbils (Meriones unguiculatus) was obtained using a Digiscan automated animal activity monitoring system. Spontaneous motor activity data were collected over 1 h (5-min samples) for groups of male and female gerbils ranging from 26-341 days of age (26, 38, 62, 116, 151, 172, 196, 247, and 341). Variables examined included: total distance travelled, average distance per movement, average speed, number of horizontal movements, time in horizontal movement, time per horizontal movement, number of vertical movements, time in vertical movement, and time per vertical movement. Age had a significant effect on spontaneous activity; all measures of horizontal activity increased from preadulthood (26 and 38 days) and remained relatively constant thereafter for adults (62+ days). Vertical activity (rearing) measures were found to increase from the 62-day-old group to the 151- and 172-day-old groups and then decrease among the older groups (196+ days). Across the 12 samples, within sessions, all horizontal and vertical activity measures (except average speed) declined for both males and females. Habituation was more rapid for the preadults than for the adults on all horizontal measures except average distance per movement. No consistent sex differences in locomotor activity were found.