Sexual play behavior in lambs androgenized in utero.

In lambs, play behavior, mainly including male-like sexual behavior patterns, is observed during weeks 4-8 following birth. The higher frequency of this behavior in male lambs has no obvious relationships with secretions of testosterone during infancy. In our experiment, pregnant ewes received subcutaneous implants of testosterone on gestation day 50. The frequency of male-like sexual patterns did not differ reliably between female lambs born to treated ewes and male lambs born to treated or control ewes. However, the frequency was lower for female control lambs. These results suggest that sexually dimorphic social play in lambs is dependent on prenatal exposure, which seems to have a masculinized effect.