Cooperative vigilance: the guanaco´s (Lama guanicoe) key antipredator mechanism

TARABORELLI, P., GREGORIO, P., MORENO, P., NOVARO, A. AND CARMANCHAHI, P.

BEHAVIOURAL PROCESSES

ELSEVIER SCIENCE BV

Lugar: Inglaterra; Año: 2012 vol. 91 p. 82 - 89

0376-6357

The concept of sociality has been related to the effectiveness of antipredator mechanisms, including cooperative vigilance and the dilution effect. Lama guanicoe (guanaco) is a 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 on hill slopes. A benefit of social grouping in guanacos is the increased probability of survival with cooperative vigilance and not with the dilution effect. This means that a predator could be detected earlier when approaching a group than when approaching a solitary individual and could thus be avoided.