Increased vulnerability to predation results in young individuals of many species experiencing higher predation pressure than adults. Consequently, the production of antipredator-related calls by young can differ from that of the same vocalizations given by adults. Sentinel behaviour is a coordinated vigilance behaviour, where one individual climbs on an elevated position and scans the surroundings for predators, while the rest of the group is mainly foraging. Meerkat, Suricata suricatta, sentinels produce six distinct sentinel call types, which inform other group members about the perceived predation risk, resulting in the adjustment of personal vigilance behaviour in foraging group members. Here, we investigated the onset of sentinel behaviour and the ontogeny of the different sentinel call types as well as the development of individual vocal signatures in meerkats. We found that meerkats started acting as a sentinel around 200 days of age, but this was highly dependent on group size, with individuals from smaller groups exhibiting sentinel behaviour earlier than individuals from larger groups. All six sentinel call types were already present in the repertoire upon first emergence of the behaviour; however, call rates of ‘all-clear’ calls increased while ‘warning’ calls decreased with increasing experience as sentinel. Analysis of one of the most frequent sentinel calls, the double note calls, indicated that fundamental frequency, mean amplitude, duration and entropy differed consistently between individuals, but we found no effect of age. Rather, our results provide evidence that individual signatures in this call type were already developed when young meerkats first started to act as sentinel and changed little with age. To conclude, we showed little ontogenetic change in overall sentinel behaviour as well as in its vocal coordination, indicating potentially high selection pressures on antipredator behaviours, such as the sentinel system, resulting in consistent behavioural responses upon first emergence.

中文翻译：

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群体规模和经验对猫鼬哨兵呼叫行为个体发育的影响

对捕食的脆弱性增加导致许多物种的年轻个体比成年人经历更高的捕食压力。因此，年轻人发出的与反捕食者相关的呼叫可能与成年人发出的相同发声不同。哨兵行为是一种协调警戒行为，其中一个人爬上高处并扫描周围环境寻找捕食者，而其他人主要是觅食。Meerkat、Suricata suricatta，哨兵产生六种不同的哨兵叫声类型，告知其他群体成员感知到的捕食风险，从而调整觅食群体成员的个人警觉行为。这里，我们研究了哨兵行为的开始和不同哨兵呼叫类型的个体发育以及猫鼬个体声音特征的发展。我们发现猫鼬在 200 天左右开始充当哨兵，但这在很大程度上取决于群体规模，来自较小群体的个体比来自较大群体的个体更早地表现出哨兵行为。首次出现该行为时，所有六种哨兵呼叫类型都已存在于曲目中；然而，随着哨兵经验的增加，“全部清除”呼叫的呼叫率增加而“警告”呼叫减少。对最常见的哨兵呼叫之一的分析，双音符呼叫，表明基频、平均振幅、持续时间和熵在个体之间始终存在差异，但我们没有发现年龄的影响。相反，我们的结果提供的证据表明，当年轻的猫鼬开始充当哨兵并且随着年龄的增长几乎没有变化时，这种呼叫类型的个体特征已经形成。总而言之，我们在整体哨兵行为及其声音协调方面几乎没有表现出个体发生变化，这表明对反捕食者行为（例如哨兵系统）的潜在选择压力很大，导致首次出现时的行为反应一致。