Mothers modify the cost of reproduction by dynamic changes in antioxidant function and filial cannibalism.

Investment in current reproduction may negatively influence subsequent fitness. Oxidative stress has been proposed as a potential mediator of this trade-off between current and future reproductive success. However, evidence of reproduction causing oxidative stress is limited, possibly owing to compensatory mechanisms that counteract oxidative insults. Here we test the idea that organisms protect against oxidative challenges through a dynamic interaction between behavioural and physiological adjustments at different stages of reproduction. To test this idea, we manipulated maternal care in the mouthbrooding cichlid fish by allowing females to continue care (brooders) or by preventing care (non-brooders). We found that brooders depleted the pool of antioxidants as brood care progressed; however, we only observed increased oxidative DNA damage at the early stage of care relative to non-brooders, possibly owing to upregulated antioxidant protection during later stages of care. Most brooders adjusted parental investment by consuming some of their offspring during mouthbrooding. Intriguingly, the level of filial cannibalism was positively related to liver antioxidant function. These changes in antioxidant function and filial cannibalism allow parents to manage the cost of reproduction and are important for our understanding of how oxidative stress mediates life-history trade-offs.