Summary: Thünken et al. 2010

Offspring survival and future reproduction can be enhanced through the provision of parental care, which also serves to increase the inclusive fitness of the parents. Parental investment theory predicts that parents should alter the level of care they provide to young based on the quality of the brood (i.e. the reproductive value) and should trade-off current investment with future care if this is likely to enhance their own lifetime reproductive success. Thünken et al. (2010) investigated this theory in the cichlid fish Pelvicachromis taeniatus, a species characterised by intense biparental brood care. They manipulated offspring quality by altering food availability (not for adults) and compared the response of parents to offspring over a period of 4 weeks. Although females generally showed higher levels of care than males, overall parental care decreased with time as offspring matured and became less vulnerable to predation. Interestingly, parents of low-quality broods (smaller average body size) showed a greater reduction in care than parents of high-quality broods, providing support for parental investment theory. Furthermore, females raising high-quality broods were more aggressive to their mating partners than females raising low-quality broods. By adjusting care relative to brood quality, parents can conserve energy for subsequent reproductive events.