Long-distance calling is a common behaviour in animals, which has various important social functions. At a physiological level, calling is often mediated by gonadal hormones such as testosterone (T), particularly when its function is linked to intra-sexual competition for mates or territory. T also plays an important role in the development of vocal characteristics associated with dominance in humans. However, the few available studies of T and vocal behaviour in non-human primates suggest that in primates, T has less influence on call production than in other animals. We tested this hypothesis by studying the relationship between T concentrations and pant-hooting in wild male chimpanzees (Pan troglodytes schweinfurthii) of the Kanyawara community in the Kibale National Park, Uganda. We found three kinds of correlation. Hourly T averages were positively associated with hourly rates of pant-hooting. Monthly T levels were likewise correlated with monthly rates of pant-hooting after controlling for other influences such as fission-fusion rates. Finally, males with high T levels had higher peak frequency at the start of the call climax. These results suggest that T affects the production of pant-hoots in chimpanzees. This implies that the pant-hoot call plays a role in male-male competition. We propose that even in cognitively sophisticated species, endocrine mechanisms can contribute to regulating vocal production.Significance statementMany animals produce long-distance calls. The production of these calls is often modulated by gonadal hormones such as testosterone, especially if the calls are involved in competition between males for mates or territory. However, comparatively little is known about the influence of testosterone over the vocal behaviour of non-human primates, especially among great apes. In this study, we examined the relationship between testosterone and pant-hooting in wild male chimpanzees. We found that testosterone levels were associated with pant-hoot rates and one acoustic feature of the call. More specifically, males pant-hooted more often and produced pant-hoots with higher peak frequencies during periods of elevated testosterone levels. These results imply that gonadal hormones are involved in regulating vocal behaviour in chimpanzees and support the view that pant-hoots play a role in male-male competition.

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野生雄性黑猩猩睾酮与长途电话的关系

长途电话是动物的一种常见行为，具有多种重要的社会功能。在生理水平上，呼唤通常由性腺激素如睾酮 (T) 介导，特别是当它的功能与性内竞争配偶或领地有关时。T 在与人类支配地位相关的声音特征的发展中也起着重要作用。然而，关于 T 和非人类灵长类动物发声行为的少数可用研究表明，在灵长类动物中，T 对呼叫产生的影响比其他动物要小。我们通过研究乌干达基巴莱国家公园 Kanyawara 社区的野生雄性黑猩猩 (Pan troglodytes schweinfurthii) 的 T 浓度与喘气之间的关系来验证这一假设。我们发现了三种相关性。每小时 T 平均值与每小时的喘气率呈正相关。在控制裂变融合率等其他影响因素后，每月 T 水平同样与每月喘气率相关。最后，具有高 T 水平的男性在呼叫高潮开始时具有更高的峰值频率。这些结果表明，T 会影响黑猩猩发出的喘气声。这意味着喘气声在男性-男性竞争中起作用。我们提出，即使在认知复杂的物种中，内分泌机制也有助于调节声音的产生。意义陈述许多动物会产生长途呼叫。这些叫声的产生通常受到睾丸激素等性腺激素的调节，尤其是当这些叫声涉及雄性之间争夺配偶或领地时。然而，关于睾酮对非人类灵长类动物（尤其是类人猿）声音行为的影响，人们知之甚少。在这项研究中，我们检查了野生雄性黑猩猩的睾丸激素和喘气之间的关系。我们发现睾酮水平与喘气率和呼叫的一种声学特征有关。更具体地说，在睾酮水平升高期间，男性更频繁地发出喘气声，并产生具有更高峰值频率的喘气声。这些结果表明，性腺激素参与调节黑猩猩的发声行为，并支持这样的观点，即喘气在雄性与雄性竞争中发挥作用。我们检查了野生雄性黑猩猩的睾酮和喘气之间的关系。我们发现睾酮水平与喘气率和呼叫的一种声学特征有关。更具体地说，在睾酮水平升高期间，男性更频繁地发出喘气声，并产生具有更高峰值频率的喘气声。这些结果表明，性腺激素参与调节黑猩猩的发声行为，并支持这样的观点，即喘气在雄性与雄性竞争中发挥作用。我们检查了野生雄性黑猩猩的睾酮和喘气之间的关系。我们发现睾酮水平与喘气率和呼叫的一种声学特征有关。更具体地说，在睾酮水平升高期间，男性更频繁地发出喘气声，并产生具有更高峰值频率的喘气声。这些结果表明，性腺激素参与调节黑猩猩的发声行为，并支持这样的观点，即喘气在雄性与雄性竞争中发挥作用。