Reproduction includes two energy investments—the energy in the offspring and the energy expended to make them. The former is well understood, whereas the latter is unquantified but often assumed to be small. Without understanding both investments, the true energy costs of reproduction are unknown. We present a framework for estimating the total energy costs of reproduction by combining data on the energy content of offspring (direct costs) and the metabolic load of bearing them (indirect costs). We find that direct costs typically represent the smaller fraction of the energy expended on reproduction. Mammals pay the highest reproductive costs (excluding lactation), ~90% of which are indirect. Ectotherms expend less on reproduction overall, and live-bearing ectotherms pay higher indirect costs compared with egg-layers. We show that the energy demands of reproduction exceed standard assumptions.

中文翻译：

---

代谢负荷和后生动物繁殖的成本


繁殖包括两项能源投资——后代的能量和产生后代所消耗的能量。前者很好理解，而后者则无法量化，但通常被认为很小。如果不了解这两项投资，再生产的真正能源成本就不得而知。我们提出了一个框架，通过结合后代的能量含量（直接成本）和生育后代的代谢负荷（间接成本）的数据来估计繁殖的总能量成本。我们发现，直接成本通常只占繁殖所消耗能量的一小部分。哺乳动物付出的繁殖成本最高（不包括哺乳期），其中约 90% 是间接成本。总体而言，变温动物在繁殖上的花费较少，与卵生动物相比，活产变温动物支付的间接成本更高。我们表明，再生产的能量需求超出了标准假设。