Factors affecting spontaneous ejaculation of male guinea-pigs.

Dominance or submissiveness of grouped male guinea-pigs was a factor in their spontaneous ejaculation rate when the males were later isolated. The ejaculation output of the dominant males was greater and more frequent than that of the submissive males. The mounting of submissive males by their dominant partners before isolation may explain the difference in their ejaculation rates. The frequency peak of spontaneous ejaculations was in the morning.