Ruppli Charlène A, Dreiss Amélie N, Roulin Alexandre
Department of Ecology and Evolution, University of Lausanne, Building Biophore, 1015, Lausanne, Switzerland.
Anim Cogn. 2013 Nov;16(6):993-1000. doi: 10.1007/s10071-013-0634-y. Epub 2013 Apr 19.
Assessing the amount of rivals is crucial to optimally adjust investment into a contest. If laboratory animals show numerical abilities, little is known about the ecological implications particularly in young animals. The two to nine barn owl (Tyto alba) siblings vocally compete for priority of access to food resources before parents actually deliver them. In dyads, the individual that vocalizes at the highest rate in the absence of parents deters its siblings from competing for next delivered prey. We tested the novel hypothesis that to optimally adjust vocal investment, barn owl nestlings assess how many of their siblings are currently competing. To singleton owlets, we broadcasted a fixed global number of calls emitted by one, two or four pre-recorded unfamiliar nestlings. We could thus distinguish the independent effect on singletons' vocal behavior of the global number of calls produced by a brood from the number of competitors that produced these calls. Overall, nestlings retreated more from vocal contest when facing more competitors. However, in front of one highly motivated competitor, nestlings refrained from vocalizing to a larger extent than when competing against more but less motivated individuals. Therefore, young animals assess variation in the number of currently competing siblings based on individual-specific vocal cues.
评估对手数量对于在竞争中优化投资至关重要。如果实验动物表现出数字能力，那么对于其生态意义，尤其是在幼小动物中的生态意义，我们了解得还很少。两到九只仓鸮（Tyto alba）的兄弟姐妹会在父母实际提供食物之前，通过鸣叫争夺获取食物资源的优先权。在成对的情况下，在没有父母时鸣叫频率最高的个体能阻止其兄弟姐妹争夺下一次送来的猎物。我们测试了一个新的假设，即仓鸮雏鸟为了优化鸣叫投资，会评估当前有多少兄弟姐妹在竞争。对于单独的雏鸟，我们播放了由一、二或四只预先录制的陌生雏鸟发出的固定总数的叫声。这样我们就能区分一窝雏鸟发出的叫声总数对单独雏鸟鸣叫行为的独立影响，以及发出这些叫声的竞争者数量的影响。总体而言，当面对更多竞争者时，雏鸟会更多地从鸣叫竞争中退缩。然而，在面对一个积极性很高的竞争者时，雏鸟比在与更多但积极性较低的个体竞争时，更会抑制鸣叫。因此，幼小动物会根据个体特有的鸣叫线索来评估当前竞争的兄弟姐妹数量的变化。
