State-dependent decisions in long-term fasting king penguins, Aptenodytes patagonicus, during courtship and incubation

Gauthier-Clerc, M Le Maho, Y Gendner, JP Durant, J Handrich, Y

M. Gauthier-clerc et al., State-dependent decisions in long-term fasting king penguins, Aptenodytes patagonicus, during courtship and incubation, ANIM BEHAV, 62, 2001, pp. 661-669

32

INGLESE

Article

Animal Sciences","Neurosciences & Behavoir

ANIMAL BEHAVIOUR

0003-3472 → ACNP

62

2001

4

661 - 669

ISI

0003-3472(200110)62:<661:SDILFK>2.0.ZU;2-N

Using an automatic identification and weighing system, we investigated chan ges in adult body mass in relation to reproductive behaviour during courtsh ip and incubation in free-living king penguins. Despite stressful nutrition al conditions and variability of fast length, the majority of pairs incubat ed successfully by accumulating large body reserves before fasting, which p rovided flexibility in fasting strategies. Our data indicate a low body mas s during fasting below which males either delayed or stopped breeding: (1) at 12 kg, the mate interruped courtship to replenish his body reserves at s ea before re-engaging in courtship; and (2) when body mass dropped to 9 kg during incubation, the male deserted the egg. The behavioural decision to g o to sea was not controlled by the time spent fasting, but by the amount of body reserves. In deserting males, the depletion of body reserves during i ncubation before relief by the females was due to a lower stored energy ( - 2 kg) at the onset of courtship compared with successful males. Unsuccessf ul males weighed only 12 kg when they started to court, and consequently ha d no safety margin that allowed them to wait for a delayed female. The unus ual depletion of body reserves of male breeders caused only 3% of incubatio n attempts to fail. Compared with successful pairs, their female partners g ained less body mass at sea ( - 40 g/day) and made a slightly longer foragi ng trip (+5 days). We suggest that the deserting males had risked breeding with the lowest fasting safety margin possible, rather than breeding later that year. However, the low body mass at desertion did not affect the pengu ins' survival or their feeding capacity, and therefore did not compromise a nother breeding attempt during the next season. (C) 2001 The Association fo r the Study of Animal Behaviour.