西藏拉萨越冬黑颈鹤家庭群的警戒同步性

以往关于动物警戒行为的研究多以经典随机独立模型为基础,然而,近期一些理论和实证研究则向该模型发出了挑战。根据警戒行为同步性程度的不同,集体警戒可能存在基于模仿的同步警戒和避免重复的协调警戒两种模式。研究了中国雅鲁藏布江自然保护区越冬黑颈鹤家庭群的警戒行为,通过独立样本t检验验证由于年龄和是否携幼所导致的个体警戒水平的差异,通过单因素方差分析比较不同类型家庭群的集体警戒水平,通过配对t检验比较集体警戒的实际观测值和独立假设下的预期值从而确定越冬黑颈鹤家庭群的警戒同步性。结果表明家庭群中的幼年黑颈鹤警戒行为时间显著低于成年黑颈鹤,但幼鹤的存在对成鹤的警戒水平没有显著影响。不同类型黑颈鹤家庭群的集体警戒水平没有差异,但并未如预期表现为同步警戒。警戒行为模式是动物在特定环境中的适应性表现,越冬黑颈鹤生境中不存在落后目标策略的捕食者和高强度的捕食风险,因而可能不足以诱发以降低捕食风险为主要功能的高强度的警戒行为同步性;同时,在资源匮乏的冬季对食物获取的优先性可能也削弱了对同步警戒的需求。

Vigilance synchronization of wintering black-necked crane (Grus nigricollis) families in Tibet

Most previous studies of animal vigilance behavior have been based on Pulliam''s classical model, which emphasizes that individuals'' vigilance occurs independently and is, therefore, unaffected by the vigilant state of other individuals in the same group. However, recent theoretical and empirical studies have challenged this model and have reported that, depending on the degree of vigilance synchronization, the collective vigilance can be either imitation-based synchronized vigilance or coordinated vigilance that avoids overlapping bouts. In the present study, we observed the vigilance behavior of wintering black-necked crane (Grus nigricollis) families in the Yarlung Zangbo River Nature Reserve. The black-necked crane is a globally endangered species that lives exclusively in the Tibetan Plateau. We captured videos in the field and then scanned 30-s intervals of the footage to record individual and collective vigilance behavior. Further, we used Student''s t-test to determine the effects of age and predation vulnerability at the individual level. The results indicated that juveniles spent significantly less time in vigilance than their parents, mainly owing to lack of vigilance and feeding experience, which necessitates juveniles to spend more time feeding to meet their energetic and developmental requirements. However, the presence of juveniles in family groups had no effect on the vigilance of adult cranes, and according to one-way ANOVA, there was no difference in the collective vigilance of different types of black-necked crane family groups. Meanwhile, a paired t-test, which was used to compare the observed and predicted collective vigilance values in order to determine the vigilance synchronization of wintering black-necked cranes, indicated that there was no synchronization tendency. The difference between the predicted and observed values was not significant between adult cranes, all family members, or adults and juveniles. Vigilance patterns are adaptive behaviors of animals in particular environments. In the wintering habitat of black-necked cranes, there is no targeting predator, and the black-necked cranes are generally protected as a symbol of auspiciousness in the Tibetan area. Although black-necked cranes that forage in farmland are inevitably disturbed by humans, the degree of interference and predation risk is insufficient to induce high-intensity vigilance synchronization that mainly function for reducing predator risk. In addition, when food availability becomes a key factor for survival, energy acquisition takes precedence over safety assurance, and as a result, the need for synchronized vigilance is reduced. Studying vigilance synchronization can reveal the vigilance pattern of black-necked cranes in the field and provide meaningful information for their management and conservation.