Prolactin and parental behavior in adelie penguins: Effects of absence from nest, incubation length, and nest failure

Adelie penguin (Pygoscelis adeliae) males and females, nesting in Antarctic a, alternate attendance at the nest with absences of many days to forage at sea. We investigated the importance of tactile input from egg and chicks o n prolactin levels by observing nest attendance patterns and obtaining bloo d samples (1) during the first nest exchange of the incubation stage, (2) f rom birds whose incubation period was artificially increased or decreased b y about 10 days, and (3) from birds whose nests had failed, Prolactin level s in females after 8 to fl days of absence from the breeding colony did not differ from those in incubating males and did not change after females res umed incubation. Moving eggs between nests resulted in nests in which chick s hatched after about 26, 36 (normal), or 46 days. Duration of incubation d id not affect prolactin levels in the parents measured during incubation, a t the pip stage, hatch stage, or early brood Stage. Adults first left their Chicks unguarded on about the same calendar date, regardless of chick age. However, chicks from long incubation nests averaged 8 days younger when th ey were Left unguarded than chicks from control or short incubation nests. In females, there was no effect of nest failure on prolactin levels. In mal es, prolactin levels were slightly lower after nest failure than in males t ending nests. Testosterone was significantly higher in males after nest fai lure than in males still tending nests. Prolactin is elevated in Adelie pen guins as part of the program of cyclical hormonal changes that accompany th e lengthy reproductive season and is relatively independent of tactile inpu t. Sustained prolactin secretion is probably required for the maintenance o f parental behavior in offshore feeding species that must be absent from th e nest for many days at a time. (C) 2000 Academic Press.