Marmoset activity behaviors recorded during ten-minute behavioral observations. The average number per minute (± SE) of transitions between quadrants of the cage, leaping, grooming, hanging (stretch), scent mark and genital displays. Geriatric marmosets made significantly fewer transitions between quadrants of the cage than did young animals (F(1, 37)=14.126, p = 0.001), as well as performing fewer leaps (F(1,37) = 24.48, p = 0.0001).