Duet-splitting and the evolution of gibbon songs

Unlike the great apes and most other primates, all species of gibbons are known to produce elaborate, species-specific and sex-specific patterns of vocalisation usually referred to as "songs". In most, but not all, species, mated pairs may characteristically combine their songs in a relatively rigid pattern to produce coordinated duet songs. Previous studies disagree on whether duetting or the absence of duetting represented the primitive condition in gibbons. The present study compares singing behaviour in all gibbon species. Various vocal characteristics were subjected to a phylogenetic analysis using previously published phylogenetic trees of the gibbon radiation as a framework. Variables included the degree of sex-specificity of the vocal repertoire, the occurrence of solo songs, and the preference for a specific time of day for song-production. The results suggest the following scenario for the evolution of gibbon songs: (1) The last common ancestor of recent gibbons produced duet songs. (2) Gibbon duets probably evolved from a song which was common to both sexes and which only later became separated into male-specific and female-specific parts (song-splitting theory). (3) A process tentatively called "duet-splitting" is suggested to have led secondarily from a duetting species to a non-duetting species, in that the contributions of the pair-partners split into temporally segregated solo songs. This appears to be the first time that a non-duetting animal can be shown to be derived from a duetting form. (4) The return to exclusive solo singing may be related to the isolated island distribution of the non-duetting species.     

Mechanical energy oscillations of two brachiation gaits: measurement and simulation

How do arm‐swinging apes locomote effectively over a variety of speeds? One way to reduce the metabolic energy cost of locomotion is to transfer energy between reversible mechanical modes. In terrestrial animals, at least two transfer mechanisms have been identified: 1) a pendulum‐like mechanism for walking, with exchange between gravitational potential energy and translational kinetic energy, and 2) a spring‐like mechanism for running, where the elastic strain energy of stretched muscle and tendon is largely returned to reaccelerate the animal. At slower speeds, a brachiator will always have at least one limb in contact with the support, similar to the overlap of foot contact in bipedal walking. At faster speeds, brachiators exhibit an aerial phase, similar to that seen in bipedal running. Are there two distinct brachiation gaits even though the animal appears to simply swing beneath its overhead support? If so, are different exchange mechanisms employed? Our kinetic analysis of brachiation in a white‐handed gibbon (Hylobates lar) indicates that brachiation is indeed comprised of two mechanically distinct gaits. At slower speeds in “continuous contact” brachiation, the gibbon utilizes a simple pendulum‐like transfer of mechanical energy within each stride. At faster speeds in “ricochetal” brachiation, translational and rotational kinetic energy are exchanged in a novel “whip‐like” transfer. We propose that brachiators utilize the transfer between translational and rotational kinetic energy to control the dynamics of their swing. This maneuver may allow muscle action at the shoulder to control the transfer and adjust the ballistic portion of the step to meet the requirements for the next hand contact. Am J Phys Anthropol 115:319–326, 2001. © 2001 Wiley‐Liss, Inc.     

被动声学监测技术在西黑冠长臂猿监测中的应用

近年来, 被动声学监测技术被广泛应用于陆生哺乳动物的监测, 它能以较低的价格和非侵入的方式在特定区域进行野生动物无人值守监测, 面临的主要问题是需要人工收回数据和后期数据分析整理较为困难。本研究设计了一套被动声学监测系统用于西黑冠长臂猿(Nomascus concolor)监测, 监测系统在野外由太阳能供电, 使用自研的指向性拾音器阵列采集鸣声数据, 并通过无线网桥实时传输数据至管护局办公楼的服务器进行存储, 通过后台的鸣声数据管理系统辅助研究人员识别鸣声和辨认鸣声来源方向, 简化数据采集和处理流程。该系统在哀牢山国家级自然保护区枇杷箐科研监听点对两个西黑冠长臂猿群体进行了351天的连续监测, 特点为: 系统运行长期稳定, 数据通过无线方式传输便捷高效且不受季节天气影响。指向性拾音器阵列能有效分辨长臂猿鸣声来源方向, 弥补了传统监测设备难以分辨鸣声方向的缺陷。该系统与现有人工监测方法相比在数据采集的持续性、连续性、完整度以及鸣声数据处理智能化和监测成本方面均具有一定优势, 符合西黑冠长臂猿持续长期监测需求, 未来可作为西黑冠长臂猿自动化监测的解决方案进行推广应用。     

高黎贡山赧亢白眉长臂猿食性及日取食量

通过确定白眉长臂猿的取食特征及日取食量,探讨不同个体间和春、秋季间日取食量是否存在差异,分析影响日取食量和取食特征的因素,为白眉长臂猿日能量需求及其营养容纳量研究奠定基础。2007—2008年春、秋季,在高黎贡山赧亢采用焦点动物取样法观察和记录数据。结果发现,白眉长臂猿取食36种食物的40个部位,其果实的食物单元、取食速度、单个鲜重值等取食特征不同于嫩叶。春、秋季白眉长臂猿每日取食果实量所占百分比最高、嫩叶所占百分比次之、茎和花所占百分比最低。春、秋季家群中雌猿的日取食量均高于雄猿。与家群的雌猿相比,独猿(♀)春季的日取食量稍高。在春季,独猿取食果实持续时间约为家群的2倍,而取食嫩叶的则与家群几乎相等。相同个体秋季的日取食量高于春季的,且春、秋季日取食各部位的量所占百分比也不同。分析结果表明,食性及日取食部位的量反映了白眉长臂猿选择食物的最基本策略。雌雄个体大小差异、能量消耗、食物特征、动物生理需求等因素影响白眉长臂猿的日取食量。白眉长臂猿取食持续时间与觅食树的食物资源量相关。     

Infanticide and the evolution of pair bonds in nonhuman primates

Social relationships between adult males and females vary widely among mammals. In general, interactions between the sexes, particularly those of an affiliative nature, are associated with and, indeed, often limited to the period of copulation or female estrus.¹ Nevertheless, cohesive male-female bonds persist beyond estrus in some species, particularly nonhuman primates,² for reasons that remain largely obscure. Protection from male infanticide has been offered as a potential benefit to females of bonds with males in a variety of primates, including mountain gorillas and gibbons. Here I evaluate this hypothesis within a comparative framework that considers alternative costs and benefits of social relationships between the sexes.     

The bronchial tree and lobular division of the lung of the white handed gibbon

The bronchial tree and lobular division of the lungs of four white handed gibbons (Hylobates agilis) were examined from the viewpoint of comparative anatomy, based upon the fundamental structure of the bronchial ramifications of the mammalian lung (Nakakuki, 1975, 1980). The right lung of the white handed gibbon consists of the upper, middle, lower, and accessory lobes, whereas the left lung consists of the middle and lower lobes. Each lobe is separated by the interlobular fissure, on both sides. The right and left lungs have the dorsal bronchiole system, lateral bronchiole system, and ventral bronchiole system. The medial bronchiole system is lacking on both sides. In the right lung, the upper lobe is formed by the first branch of the dorsal bronchiole system. The middle lobe is formed by the first brach of the lateral bronchiole system, and the accessory lobe by the first branch of the ventral bronchiole system. The remaining bronchioles constitute the right lower lobe. In the left lung, the upper lobe bronchiole, which is the first branch of the dorsal bronchiole system, is lacking. Therefore, the middle lobe bronchiole, i.e. the first branch of the lateral bronchiole system, is well developed. The accessory lobe bronchiole, the first branch of the ventral bronchiole system, is also lacking. The remaining bronchioles constitute the left lower lobe. These features were compared with those of other apes and man.     

Type locality of Hylobates concolor leucogenys

Kloss [1929] restricted the type locality of the northern white-cheeked gibbon, Hylobates concolor leucogenys, on the basis of two specimens that were collected at Muang Khi, Laos, not at Muang Pak-Lay, Laos, as conventionally assumed. The locality difference is zoogeographically important because Muang Khi is east of the Mekong River, within the known range of H. c. leucogenys, whereas Muang Pak-Lay is west of the river, outside the known range of the subspecies. The type-locality restriction is appropriately amended.