We all know that having kids is expensive, but that truth is more universal than you might think. Across animal species, bearing offspring may be as much as 10 times as energetically costly as previously assumed, according to a new study published May 16 in Science. Specifically, the indirect metabolic costs for mothers carrying young have been seriously underestimated in past biological theories, according to the authors.
The studies included in the meta-analysis were ones containing data on how much energy individual animals were burning at baseline, energy used while carrying eggs or young, and/or offspring energy content. From this past research, the authors pooled the disparate data, and created a simple mathematical model for understanding both the direct and indirect costs of reproduction.