Sex differences in rats' stationary-cage activity measured by observation and automatic recording

Rats' stationary-cage activity was measured using simultaneous observational time sampling and automatic recording via photobeams, Females scored higher than males on the combined observational categories of rearing, ambulating, and sniffing, but lower on grooming, eating, and drinking, with these differences consistent across 9 days of confinement and across time of day of observation. There were no sex differences in the time spent inactive or in the number of photobeam breaks. Beam breaks were related positively to sniffing and inversely to inactivity. The results raise questions regarding the interpretation of sex differences in behavior in novel and familiar environments and provide evidence on the comparability of observational and automatic methods of activity measurement.