In a replicated experiment, nonbreeding winter populations of Microtus montanus were given supplements of rolled oats coated with 6-methoxybenzoxazolinone, a naturally occurring plant derivative. After 3 weeks of this feeding regime, samples from the populations demonstrated a high incidence of pregnancy in females and testicular hypertrophy in males. Control populations receiving rolled oats coated only with the solvent showed no reproductive activity. These results demonstrate that the presence of 6-methoxybenzoxazolinone in the plant food resource acts as the ultimate cue to trigger reproductive effort in Microtus montanus.

A plant-derived cyclic carbamate, 6-methoxybenzoxazolinone, that stimulates reproductive activity in Microtus montanus has been isolated. This nonestrogenic compound may be a naturally occurring environmental cue affecting reproductive cycles in many mammals.

Naturally occurring cinnamic acids and their related vinylphenols were found to inhibit reproductive function in Microtus montanus. When fed on these compounds, the rodents exhibited decreased uterine weight, inhibition of follicular development, and a cessation of breeding activity. It is suggested that these animals utilize plant compounds as a cue to terminate their reproductive effort in natural populations.