Animal Behaviour, Zoological Institute, University of Zurich, Winterthurerstrasse 190, Zurich, Switzerland.
Am Nat. 2009 Mar;173(3):400-10. doi: 10.1086/596541.
A major evolutionary force driving functionally referential alarm calls is the need for different strategies to escape various predator types in complex structured habitats. In contrast, a single escape strategy appears to be sufficient in less-structured open habitats, and under such conditions urgency-dependent alarm calls may be favored. Nevertheless, some species, such as meerkats (Suricata suricatta), have evolved functionally referential alarm calls despite living in open areas, using only bolt-holes for retreat. To understand the evolution of different alarm call systems, we investigated the calls of sympatric Cape ground squirrels (Xerus inauris) and compared their antipredator and foraging behavior with that of meerkats. Cape ground squirrels emitted urgency-dependent alarm calls and responded to playbacks depending on urgency, not predator type. Vigilance behavior and habitat use differed between the two species. Meerkats roam widely to find prey and for efficient foraging depend on coordinated predator vigilance and escape behavior. As herbivores with smaller territories, Cape ground squirrels depend less on coordinated antipredator behavior, and urgency-dependent alarm calls encode all essential information. We conclude that habitat complexity does not explain the evolution of functionally referential alarm calls in all species, and other constraints, such as the need to coordinate group movements to maintain foraging efficiency, could be more relevant.
推动具有功能意义的警报叫声进化的主要力量是在复杂结构的栖息地中，不同的物种需要不同的策略来逃避各种捕食者。相比之下，在结构较少的开放栖息地中，似乎只需要一种单一的逃避策略，在这种情况下，依赖紧急程度的警报叫声可能更有优势。然而，有些物种，如猫鼬（Suricata suricatta），尽管生活在开放区域，只使用藏身之处作为撤退的地方，但它们已经进化出了具有功能意义的警报叫声。为了理解不同警报叫声系统的进化，我们调查了同域分布的海角地松鼠（Xerus inauris）的叫声，并将它们的捕食防御行为与猫鼬进行了比较。海角地松鼠发出依赖紧急程度的警报叫声，并根据紧急程度而不是捕食者类型做出反应。两种物种的警戒行为和栖息地使用方式不同。猫鼬广泛漫游以寻找猎物，为了有效地觅食，它们依赖于协调一致的捕食者警戒和逃跑行为。作为拥有较小领地的食草动物，海角地松鼠较少依赖协调一致的捕食防御行为，而依赖紧急程度的警报叫声则可以传达所有必要的信息。我们的结论是，栖息地的复杂性并不能解释所有物种中具有功能意义的警报叫声的进化，其他限制因素，如协调群体运动以维持觅食效率的需求，可能更为重要。
