Department of Zoology, University of Melbourne, Parkville, Victoria 3010, Australia.
Biol Lett. 2011 Dec 23;7(6):859-62. doi: 10.1098/rsbl.2011.0526. Epub 2011 Jul 6.
Lactation is the most energetically expensive component of reproduction in mammals. Theory predicts that reproducing females will adjust their behaviour to compensate for increased nutritional demands. However, experimental tests are required, since comparisons of the behaviour of naturally reproducing and non-reproducing females cannot distinguish between true costs of reproduction, individual differences or seasonal variation. We experimentally manipulated reproduction in free-ranging, eastern grey kangaroos (Macropus giganteus), using a fertility control agent. Our novel field experiment revealed that females altered their behaviour in direct response to the energetic demands of reproduction: reproducing females increased bite rates, and thus food intake, when the energetic demands of lactation were highest. Reproducing females did not reduce the time spent on vigilance for predators, but increased their forage intake on faecal-contaminated pasture, thereby increasing the risk of infection by gastrointestinal parasites-a largely unrecognized potential cost of reproduction.
哺乳是哺乳动物繁殖中最耗费能量的环节。理论预测，繁殖雌性动物会调整行为以适应营养需求的增加。然而，由于自然繁殖和非繁殖雌性动物行为的比较不能区分繁殖的真正成本、个体差异或季节性变化，因此需要进行实验测试。我们使用一种生育控制剂，对自由放养的东部灰袋鼠（Macropus giganteus）进行了繁殖的实验操作。我们新颖的野外实验表明，雌性动物会直接对繁殖的能量需求做出行为上的改变：当哺乳的能量需求最高时，繁殖的雌性动物会增加咀嚼速度，从而增加食物摄入量。繁殖的雌性动物并没有减少对捕食者的警戒时间，但增加了对粪便污染牧场的采食，从而增加了感染胃肠道寄生虫的风险——这是一个很大程度上被忽视的繁殖潜在成本。
