Reproduction and mortality rates in ecologically distinct species of murid rodents

The trade-off between reproduction and somatic maintenance is one of the most studied concepts of modern evolutionary ecology. This theory predicts a negative relationship between maximum species longevity and total reproductive output. However, studies performed on natural animal populations have found contradictory results, probably due to the unlikelihood of wild animals gaining both maximum longevity and maximum potential fecundity. A comparison of the mortality rates and reproductive output of four ecologically distinct rodent species of Cricetidae family that were maintained in the laboratory in controlled conditions revealed the different life-history tactics of subterranean social mole voles and three related aboveground species: hydrophilic water voles, arid dwarf hamsters and steppe lemmings. Regardless of the relatively higher mortality rates at early ages in mole voles, this species has considerably higher maximum species longevity and smaller litter sizes that do not depend on calendar age, whereas in dwarf hamsters and water voles clear negative correlations between female age and litter size were detected. Steppe lemmings, as a semi-social arid species, shared some life-history tactics with both mole voles and aboveground non-social rodents.