Krams Indrikis, Krama Tatjana
Department of Sciences, Daugavpils University, LV-5400 Daugavpils, Latvia.
Proc Biol Sci. 2002 Nov 22;269(1507):2345-50. doi: 10.1098/rspb.2002.2155.
When prey animals discover a predator close by, they mob it while uttering characteristic sounds that attract other prey individuals to the vicinity. Mobbing causes a predator to vacate its immediate foraging area, which gives an opportunity for prey individuals to continue their interrupted daily activity. Besides the increased benefits, mobbing behaviour also has its costs owing to injuries or death. The initiator of mobbing may be at increased risk of predation by attracting the predator's attention, especially if not joined by other neighbouring prey individuals. Communities of breeding birds have always been considered as temporal aggregations. Since an altruist could not prevent cheaters from exploiting its altruism in an anonymous community, this excluded any possibility of explaining mobbing behaviour in terms of reciprocal altruism. However, sedentary birds may have become acquainted since the previous non-breeding season. Migrant birds, forming anonymous communities at the beginning of the breeding season, may also develop closer social ties during the course of the breeding season. We tested whether a male chaffinch, a migrant bird, would initiate active harassment of a predator both at the beginning of the breeding season and a week later when it has become a member of a non-anonymous multi-species aggregation of sedentary birds. We expected that male chaffinches would be less likely to initiate a mob at the beginning of the breeding season when part of an anonymous multi-species aggregation of migratory birds. However, their mobbing activity should increase as the breeding season advances. Our results support these predictions. Cooperation among individuals belonging to different species in driving the predator away may be explained as interspecific reciprocity based on interspecific recognition and temporal stability of the breeding communities.
当被捕食动物发现附近有捕食者时，它们会一边发出吸引其他被捕食个体靠近的特征性声音，一边对捕食者进行围攻。围攻会使捕食者离开其当前的觅食区域，这为被捕食个体提供了继续被打断的日常活动的机会。除了增加的益处外，围攻行为也有其代价，比如受伤或死亡。围攻的发起者可能会因吸引捕食者的注意而面临更高的被捕食风险，尤其是在没有其他邻近被捕食个体加入的情况下。繁殖鸟类群落一直被视为临时聚集群体。由于利他主义者无法在一个匿名群体中阻止作弊者利用其利他行为（的好处），这就排除了用互惠利他主义来解释围攻行为的任何可能性。然而，定居鸟类可能自上一个非繁殖季节以来就已经相互熟悉。在繁殖季节开始时形成匿名群体的候鸟，在繁殖季节过程中也可能发展出更紧密的社会联系。我们测试了雄性苍头燕雀（一种候鸟）在繁殖季节开始时以及一周后（此时它已成为一个由定居鸟类组成的非匿名多物种聚集群体的一员）是否会主动骚扰捕食者。我们预计，当雄性苍头燕雀作为候鸟匿名多物种聚集群体的一部分时，在繁殖季节开始时发起围攻的可能性较小。然而，随着繁殖季节的推进，它们的围攻活动应该会增加。我们的结果支持了这些预测。不同物种个体之间在驱赶捕食者方面的合作可以解释为基于种间识别和繁殖群落时间稳定性的种间互惠行为。
