Taraborelli Paula, Gregorio Pablo, Moreno Pablo, Novaro Andrés, Carmanchahi Pablo
Laboratorio de Desertificación y Ordenamiento Territorial, IADIZA, CCT-Mendoza, CONICET, Argentina.
Behav Processes. 2012 Sep;91(1):82-9. doi: 10.1016/j.beproc.2012.06.002. Epub 2012 Jun 13.
The concept of sociality has been associated with the effectiveness of antipredator mechanisms, like cooperative vigilance and the dilution effect. Lama guanicoe (guanaco) is a social native herbivore in South America and a social species. The objectives of this study were to evaluate the antipredator responses of different-sized groups of guanacos in areas with varying predation risks and to determine antipredator mechanisms in guanacos. For this, we measured different antipredator responses to a potential predator (human subjects). Detection of predator and flight distances from predator both increased with a greater number of guanacos per group and with greater distances among guanacos within the social group. Both buffer distance and flight time decreased with a greater number of guanacos per group, but increased with greater distances among guanacos inside the social group. Solitary adult males moved shorter distance and mixed groups moved greater distances. Flight distances were greater in areas with tall and dense vegetation than in areas with low vegetation. Buffer distance and flight time were shorter in undulating land than on flat lands, and groups were usually observed on hill slopes. Our results suggest that the benefit of social grouping in guanacos is the increased probability of avoiding predator with cooperative vigilance and not with the dilution effect. This means that a predator could be detected earlier when approaching a guanaco group than when approaching a solitary individuals and could thus be avoided.
社会性的概念一直与反捕食机制的有效性相关联，比如合作警戒和稀释效应。原驼是南美洲一种社会性的本土食草动物，也是一种群居物种。本研究的目的是评估在不同捕食风险区域中不同规模原驼群体的反捕食反应，并确定原驼的反捕食机制。为此，我们测量了对潜在捕食者（人类受试者）的不同反捕食反应。对捕食者的察觉以及与捕食者之间的逃跑距离均随着每组原驼数量的增加以及群居群体中原驼之间距离的增大而增加。缓冲距离和逃跑时间均随着每组原驼数量的增加而减少，但随着群居群体中原驼之间距离的增大而增加。单独的成年雄性移动距离较短，而混合群体移动距离较远。在植被高大茂密的区域，逃跑距离比植被低矮的区域更远。起伏地形中的缓冲距离和逃跑时间比平坦地形更短，并且通常能在山坡上观察到群体。我们的结果表明，原驼群居的益处在于通过合作警戒而非稀释效应来提高躲避捕食者的概率。这意味着，捕食者在接近原驼群体时比接近单独个体时能更早被察觉，从而得以被躲避。
