The Effect of Litter Size and Litter Size Manipulations on Energetic Costs of Lactation in Grasshopper Mice.

繁殖在能量上是昂贵的，哺乳动物的成本完全由母亲通过妊娠和哺乳来承担。母亲的努力随着产仔数的增加而增加，但速度缓慢，以至于大产仔中单个后代获得的可用资源比例小于与母亲照顾水平相关的后代，因此在产仔数和后代质量之间存在权衡。不幸的是，评估这种权衡并不简单，因为母亲生产后代的效率可能不同。本研究将对北方蚱蜢小鼠的胚胎和幼崽数量进行控制，以检验产仔数量与哺乳能量消耗之间的关系。能量数据将用于测试产仔数的个体优化和测试假设，即模态产仔数每单位努力产生最大的后代。繁殖效率和成本将取决于母鼠自然饲养的产仔和人工饲养的产仔大小。该项目的研究结果将为哺乳的能量消耗、产仔数的演变和产仔数的变异提供基础数据

Reproduction is energetically costly and, in mammals, the cost is born entirely by mothers through gestation and lactation. Maternal efforts increases with litter size, but at slow rate such that individual offspring in large litters receive a smaller percentage of available resources than offspring are tied to the level of maternal care, so there is a tradeoff between litter size and offspring quality. Unfortunately, assessing this tradeoff is not simple because mothers may differ in their efficiency of producing offspring. This study will manipulate the number of embryos and pups in northern grasshopper mice to examine the relationship between litter size and the energetic cost of lactation. Energetic data will be used to test for individual optimization of litter size and to test the hypothesis that the modal litter size produces the largest offspring per unit effort. Reproductive efficiency and costs will be determined in litters where the mother is rearing natural-sized litters, and in artificially larger and smaller litters. The results of this project will provide foundation data on the energetic cost of lactation and the evolution of litter size and litter size variability