Family effects on early survival and variance in long-term reproductive success of female cheetahs.

1. While it is generally accepted that the survival of offspring within families may be correlated, the extent of correlation has been largely untested. Furthermore, the impact of such correlation on the estimated variance in females' reproductive success has rarely been quantified. 2. Here we use an exceptional data set from a long-term study of individually recognized cheetahs from the Serengeti National Park in Tanzania to formally quantify family effects in carnivores. 3. We show (i) that cubs from the same litter exhibit more similar fates than unrelated cubs when it comes to first-year survival; and (ii) that the observed variance of the long-term reproductive success of females is twice the variance expected under the assumption of complete independence of fates between cubs. 4. We suggest that family effects are likely to be widespread in vertebrates with average litter sizes > 1, and could have important consequences for population dynamics and population viability analyses.