Refeeding signal in fasting-incubating king penguins: changes in behavior and egg temperature

This study is directed toward understanding the process of feeding stimulat ion ("refeeding signal") that has been suggested to operate below a body ma ss threshold or critical metabolic status in spontaneously fasting birds. B ehavior and egg temperature (T-egg) were continuously monitored by video mo nitoring and biotelemetry, respectively, in fasting-incubating king penguin s kept in a pen to prevent relief by the partner until spontaneous egg aban donment. Penned birds fasted 10 days more and lost 1.2 kg more than birds r elieved normally by their partner, abandoning the egg about 1 wk after reac hing a critical body mass. Definitive egg abandonment was preceded by trans itory abandonments of progressively increasing duration during which time t he birds went further and further away from their egg. There were marked in terindividual differences but on average transitory abandonments began 36 /- 5 h before the definitive abandonment and were paralleled by resumption of display songs signaling the readiness of the bird to depart for feeding. T-egg was maintained at around 35.7 degrees C during normal incubation but significantly decreased the last 2 days before egg abandonment. These chan ges are interpreted as reflecting a stimulation to refeed at a threshold bo dy mass corresponding to a critical fat store depletion. Thus the fasting-i ncubating king penguin appears to be an interesting animal model for unders tanding the long-term metabolic control of feeding behavior in relation to energy status.