Methyl thiolbutyrate: a reliable correlate of estrus in the golden hamster

A volatile sulfur-containing compound that is characteristic of estrous (Day 1) hamster vaginal discharge has been identified as methyl thiolbutyrate (MTB). From numerous measurements of MTB concentration on each day of the estrous cycle, it is clear that this compound could well serve as a natural chemical signal of the estrous state of the female. Both the ability of MTB to attract male hamsters and its ability to facilitate copulatory behavior toward female surrogates were evaluated in behavioral experiments. The responses to MTB were compared to those elicited by dimethyl disulfide (DMDS), by a mixture of MTB and DMDS, by a grand mixture of MTB and DMDS with thirteen other known volatile constituents of the vaginal discharge, and by fresh vaginal discharge. In contrast to fresh vaginal discharge, none of the identified compounds or mixtures facilitated male copulatory behavior. Most of the attraction observed in the behavioral experiments could be attributed to the DMDS in the test samples. The MTB is readily converted to DMDS and may serve as a precursor of DMDS in the vaginal discharge.