Figure 1.

Plasma corticosterone (A) and oxytocin (B) levels measured by radioimmunoassay and enzyme immunoassay respectively. For males, corticosterone levels were increased in short days whereas in females aggression testing increased corticosterone levels. In females oxytocin levels were increased by aggression testing under long days but not short days. * p < 0.05 planned comparison between control and aggression, † p< 0.05 effect of photoperiod