Diurnal patterns of scent-marking, serum testosterone concentration and heart rate in male Mongolian gerbils.

ABSTRACT

The diurnal rhythms of scent marking behavior in an open-field test as well as the diurnal rhythms of serum testosterone concentration and heart rate under home cage conditions were investigated in male Mongolian gerbils. The behavioral measures of scent marking activity, sniffing frequency and locomotor activity in the open field showed a clear rhythm during the 24 hour period with a significant maximum during the dark. In contrast to this, the mean testosterone concentration was lower during the dark as compared to the light phase. The heart rate was not different during light and dark phase of the diurnal cycle, instead, bursts of increased frequency occurred approximately once per hour, both during light and dark phase.