Determinants of mating success in the golden hamster (Mesocricetus auratus): I. Male capacity.

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Abstract
Rested adult golden hamsters produced a mean of 13 ejaculations and then showed a modified copulatory pattern consisting of long intromissions (10-30 s of intravaginal thrusting) during which no sperm transfer occurs. When a 2nd (fresh) female was introduced, 58% of the males produced at least 1 more ejaculation, and 17% of the males produced 1 further ejaculation when placed with a 3rd female. In similar 3-female tests conducted 24 h later, all males ejaculated (M = 4 ejaculations); this level of ejaculatory output was maintained over a subsequent 10-day period of daily testing. Four ejaculations ensured a nearly 100% pregnancy rate and maximum ltter size in the 1st females. Second and 3rd females, however, received fewer ejaculations and subsequently showed reduced fertility and produced smaller litters. Most males showed high levels of long intromissions on all days and with all females. The physiological significance of these long intromissions may be to trigger the progestational response. Examination of the rate of recovery from sexual exhaustion indicated that 2 or 8 h of rest resulted in fewer than 50% of the males being capable of 1 further ejaculation. However, most of these single ejaculations were accompanied by long intromissions and resulted in successful pregnancies. Four to 8 days were required for full recovery of ejaculatory capacity. This study showed that the male golden hamster has a higher ejaculatory output and more rapid recovery from sexual exhaustion than other small rodents studied. Thus, the limits of male capacity appear to vary widely among species.