Behavioural and physiological effects of prolactin in incubating ring doves.

The role of prolactin in the maintenance of incubation behaviour in ring doves was re-examined and the dose-response relationships for behavioural, target tissue and body weight changes induced by injections of prolactin were compared in doves tested during the incubation phase of the breeding cycle. Doves given injections of prolactin twice a day starting on day 4 of incubation, during a 10-day period of isolation from their mates and nests, showed a higher persistence of incubation behaviour than doves injected with saline vehicle. However, the prolactin treatment failed to maintain incubation behaviour to the same extent as that observed in non-isolated untreated breeding pairs. Liver and body weights were higher and testicular weights lower in birds treated with high doses of prolactin than in non-isolated birds which had been incubating for 14 days. Good dose-response relationships were established between body, liver, crop and testes weights and the dose of prolactin administered. However, only a weak dose-response relationship was observed between prolactin and the maintenance of incubation behaviour. Overall, females injected with prolactin displayed more quiet sitting behaviour, less body weight gain and more gonadal regression than males injected with prolactin. Males in untreated breeding pairs had higher liver weights and lower crop weights than females. It is concluded that prolactin plays a role in maintaining readiness to incubate in doves, but that other factors may also contribute to this response. Further, it appears that prolactin mediates several target tissue changes which are sex-specific during incubation.