Abstract
Summary
The trade‐off between reproductive investment and lifespan is the single most important concept in life‐history theory. A variety of sources of evidence support the existence of this trade‐off, but the physiological costs of reproduction that underlie this relationship remain poorly understood. The Free Radical Theory of Ageing suggests that oxidative stress, which occurs when there is an imbalance between the production of damaging Reactive Oxygen Species (ROS) and protective antioxidants, may be an important mediator of this trade‐off. We sought to test this theory by manipulating the reproductive investment of female mice (Mus musculus domesticus) and measuring the effects on a number of life history and oxidative stress variables. Females with a greater reproductive load showed no consistent increase in oxidative damage above females who had a smaller reproductive load. The groups differed, however, in their food consumption, reproductive scheduling and mean offspring mass. Of particular note, females with a very high reproductive load delayed blastocyst implantation of their second litter, potentially mitigating the costs of energetically costly reproductive periods. Our results highlight that females use strategies to offset particularly costly periods of reproduction and illustrate the absence of a simple relationship between oxidative stress and reproduction.
We test whether oxidative stress might represent an important cost of reproductive effort. We performed a two‐factor manipulation of reproductive effort in female house mice, manipulating the number of pups in their first brood as well as the chance of them becoming pregnant post‐partum. Females with elevated greater reproductive load showed no consistent increase in oxidative damage, despite differences in food consumption, reproductive scheduling, mean offspring mass and a delay in blastocyst implantation of their second litter.