Urinary oestrogen excretion in the female cotton-topped tamarin (Saguinus oedipus oedipus)

Daily urinary oestrogen excretion was measured by radioimmunoassay in 6 adult female cotton-topped tamarins. Four females showed obvious cyclicity in oestrogen excretion and the mean cycle length for 10 complete cycles was 22.7 +/- 1.7 days with a range of 19-25 days. In 3 of the 6 females a dip-and-read test for blood in the urine gave positive readings which were distributed during trough and mid-cycle periods although females of this species are believed not to menstruate.