Department of Biological Sciences, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia V5A 1S6, Canada.
Department of Biology, George Fox University, 414 N. Meridian Street, Newberg, OR 97132, USA.
J Exp Biol. 2021 Apr 15;224(8). doi: 10.1242/jeb.235846. Epub 2021 Apr 26.
Free-living animals often engage in behaviour that involves high rates of workload and results in high daily energy expenditure (DEE), such as reproduction. However, the evidence for elevated DEE accompanying reproduction remains equivocal. In fact, many studies have found no difference in DEE between reproducing and non-reproducing females. One of the hypotheses explaining the lack of difference is the concept of an 'energetic ceiling'. However, it is unclear whether the lack of increase 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 efforts followed by both groups breeding in the low foraging effort common garden condition. DEE was measured in both sexes throughout the experiment. We show sex-specific energy management strategies in response to training for increased foraging effort prior to reproduction. Specifically, males and females responded differently to the high foraging effort treatment and subsequently to chick rearing in terms of energy expenditure. Our results also suggest that there is 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.
自由生活的动物经常会进行高工作量和高日常能量消耗（DEE）的行为，例如繁殖。然而，伴随着繁殖而导致 DEE 升高的证据仍然存在争议。事实上，许多研究发现，繁殖和不繁殖的雌性之间 DEE 没有差异。解释这种差异的假设之一是“能量上限”的概念。然而，尚不清楚能量消耗的增加是否由于存在能量上限以及/或雄性在亲代养育期间进行补偿。为了研究是否存在能量上限，我们在圈养的斑马雀（Taeniopygia guttata）中实验性地操纵觅食努力，创建了两个具有高和低觅食努力的组，然后两组都在低觅食努力的公共花园条件下繁殖。在整个实验过程中测量了两性的 DEE。我们展示了在繁殖前为增加觅食努力而进行训练时，针对性别特异性的能量管理策略。具体来说，雄性和雌性对高觅食努力处理以及随后对育雏的反应不同，就能量消耗而言。我们的结果还表明，雌性存在能量上限，并且繁殖前发生的能量成本可以以性别特异性的方式延续到繁殖的后续阶段。
