Sex-specific energy management strategies in response to training for increased foraging effort prior to reproduction

Free-living animals often engage in behaviour that involve high rates of workload and result in high daily energy expenditure (DEE), such as reproduction. However, the evidence for elevated DEE accompanying reproduction remain equivocal. In fact, many studies have found no difference in DEE between reproducing vs. non-reproducing females. One of the hypotheses explaining the lack of difference is the concept of energetic ceiling. However, it is unclear whether the lack of increases in energy expenditure is due to the existence of an energetic ceiling and/or compensation by males during parental care. To investigate whether an energetic ceiling exists we experimentally manipulated foraging effort in captive zebra finches, Taeniopygia guttata, creating two groups with high- and low foraging effort followed by both groups breeding in a low foraging effort common garden condition. DEE was measured in both sexes throughout the experiment. Our findings showed sex-specific energy management strategies in response to training for increased foraging effort prior to reproduction. Specifically, males and females responded differently to high foraging effort treatment and subsequently to chick rearing in terms of energy expenditure. Our results also suggested that there appears to be an energetic ceiling in females and that energetic costs incurred prior to reproduction can be carried over into subsequent stages of reproduction in a sex-specific manner.