Thank you for visiting nature. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser or turn off compatibility mode in Internet Explorer. In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript. To reveal the complex mechanisms associated with reproduction and investment, it is necessary to examine variations in maternal investment across species.
Comparisons across species call for a standardised method to quantify maternal investment, which remained to be developed. This paper addresses this limitation by introducing the maternal investment metric β MI β for mammalian species, established through the allometric scaling of the litter mass at weaning age by the adult mass and investment duration i. Using a database encompassing hundreds of mammalian species, we show that the metric is not highly sensitive to the regression method used to fit the allometric relationship or to the proxy used for adult body mass.
The comparison of the maternal investment metric between mammalian subclasses and orders reveals strong differences across taxa. For example, our metric confirms that Eutheria have a higher maternal investment than Metatheria. We discuss how further research could use the maternal investment metric as a valuable tool to understand variation in reproductive strategies.
In mammals, maternal investment, i. The concept of maternal investment has thus played a pivotal role in the development of life-history theory 2 and population ecology 3. Understanding the intricate relationships associated with reproduction and maternal investment is essential for comprehending how an animal can achieve adequate fitness within a specific niche 4.
Maternal investment is shaped by genetically influenced factors connected to life-history traits such as metabolic rate, body mass, and longevity, which all scale with each other due to their relationship with body size 5 , 6.
