When asked what we know about gibbons, most of us think of a long-armed non-human primate that makes a lot of noise. That’s pretty accurate. Gibbons are well known for their loud calls, which ring out across their forest homes in South-East Asia. Those of us who study them refer to these calls as ‘songs’, and a quick trip to the zoo at the right time of day explains why; these songs are not only loud, but elaborate, melodious and repetitive, giving them all the hallmarks of other animal song, including birdsong.
Although gibbons use song to communicate with distant individuals, they typically live in small family groups. Their short-range, quieter vocal communication between close relatives is something we know almost nothing about.
我们的团队是第一个从经验上调查野生白人吉本斯（Gibbons）的群体内部呼吁的人（Hylobates lar） 在泰国。虽然任何学习长臂猿的人都知道这些安静的电话无处不在，但我们对它们的含义和为什么使用它们的方式知之甚少。
更安静的呼叫是特定于上下文的，并且因性别而异
Our study表明一种类型的“ hoo”调用是由声学分析所揭示的，这是上下文特定的。这是令人惊讶的，因为在未经训练的人耳中，在所有情况下，Hoos听起来都很像。这种特异性意味着HOOS可能是在长臂猿之间有意义地传递信息的候选者。
HOO是在多种情况下生产的，包括喂食，遇到相邻的群体或捕食者，以及他们著名歌曲的前奏。我们的研究表明，所有这些之间存在细微的声学差异。
Of particular note, hoos given in response to raptor predators are acoustically distinct from all other hoos, including those produced to tigers and clouded leopards, making the raptor hoo a predator-specific hoo variant. Raptor hoos are the lowest frequency, lowest duration and most spread out temporally, making them the least audible.
This is in stark contrasts with gibbon responses to cat predators, which, although they begin with hoos, always escalate into loud song (see an earlier study of ours这里). Raptors have poor hearing at low frequency, and one possibility is that gibbons produce very quiet, low frequency calls in order to avoid detection.
有趣的是，我们还发现，雄性长臂猿声音明显高于女性声音。这与包括人类在内的其他哺乳动物的大多数证据相矛盾，并且更加令人困惑，因为吉本斯在身体大小上几乎没有性二态性。一种解释是，雌性长臂猿更喜欢倾斜声音较高的男性，而最近studyby Claudia Barelli and colleagues has suggested that male gibbon voice pitch increases with androgens.
Finding such subtle variation in just one call type – the hoo – makes the gibbons’ potential vocal repertoire much larger than previously thought. Playbacks are now needed to determine whether these differences are salient to conspecifics and therefore ‘referential’.
Helping us understand the evolution of communication
长臂猿歌曲是漫长，大声且复杂的，但我们才刚刚开始看到他们的交流曲目的程度，并暗示了基本的认知过程（请参阅我们的2006年研究这里).
A recentarticle在新的科学家中，展示了花费数小时的勤奋时间来收听安吉拉·达索（Angela Dassow）和迈克尔·科恩（Michael Coen）的长臂猿电话的回报。他们发现，白手手的长臂猿歌曲至少包含26个不同的单元（与最初描述的7个单元相比），这仅在到目前为止的一部分中。
Our study表明长臂猿的静态通话也很复杂，并且以非常微妙的方式变化：我们能够将HOO单元分成六个子单元，并且可能还有更多。与频率相关参数（例如音调）的微妙变化也可能是某些人类语言（例如泰语）的关键载体，这可能使它们变得棘手，因为它们使像我这样的西方人变得棘手。
Gibbons are extraordinarily vocal creatures, and because they are represented by 16 extant species, they give us the rare opportunity to study the evolution of complex vocal communication in a non-human primate. In the future, gibbon vocalisations may reveal much about the processes that shape vocal communication. And, because they are an ape species, they may be one of our best hopes at tracing the evolution of human communication as well.
注释