The endocrine basis of the reproductive cycle in the king penguin ( Aptenodytes patagonicus)

• Published in: Journal of Zoology
• Main Authors: Jouventin, P., Mauget, R.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1996
• Subjects: Crozet Islands
• Online Access: http://dx.doi.org/10.1111/j.1469-7998.1996.tb05421.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1469-7998.1996.tb05421.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1469-7998.1996.tb05421.x; https://zslpublications.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1469-7998.1996.tb05421.x

What is the breeding frequency of the king penguin? More than 30 years of study and five major investigations, did not answer this question owing to the length (14 months) and the spreading (four months of laying) of reproductive events. Following intensively during three consecutive years nearly 1000 tagged birds in a small colony, we obtained the individual history of a large part of the population. To these demographic and phenological studies, we have associated an endocrinological study validating blood samples and experiments in another colony. The success or failure of a breeding cycle determines the timing of the subsequent breeding attempt. At Crozet Islands, the king penguin can rear one chick every two years at best: a successful breeding is followed by unsuccessful late breeding (or by non‐breeding). So a large part of the population displays an annual periodicity of breeding attempts but with low individual breeding success. The restarting of the reproductive cycle appears basically to be annual, the pituitary responding to the photoperiod. Steroid patterns present classical variations of level according to the reproductive stage. Prolactin (PRL) and luteinizing hormone (LH) are antagonists but, in this species, PRL remains high without external stimulation. To relay after failure in the field. we have experimentally to break down endogenous PRL. So, we have demonstrated that PRL has a key role in the reproductive cycle. Paradoxically, the king penguin is an irregular breeder, quasi‐biennial, although physiologically an annual breeder. In winter, there is not enough food at sea to rear the chick and during four months, the chick fasts. So a successful breeding cycle, which can be shortened to only nine months in captivity, is extended to more than a year for ecological reasons.