“…Last, samples were collected under relatively adverse conditions (from the ground, trunks, and leaves), which might have resulted in a higher nonphysiological variance in E1C measurements compared to the measurement of samples collected in a cage situation. Studies under more controlled conditions of sample collection (e.g., cage-housed animals) are thus needed to determine whether the measurement of urinary estrone conjugates is useful for monitoring estrogen excretion during the ovarian cycle in Tonkean macaques, as in other macaques [Shideler et al, 1983[Shideler et al, , 1993Monfort et al, 1986, 19871. Following conception, urinary progestin levels remain elevated beyond the length of the luteal phase, allowing pregnancy to be detected within the first months after conception, as in other primates [Eastman et al, 1984;Shideler et al, 1985Shideler et al, ,1993Monfort et al, 1986;Heistermann & Hodges, 1994;Jurke et al, 19941. A parallel evaluation of urinary E1C concentrations which are elevated by the third week after conception can be used to confirm pregnancy.…”