Homosexual behaviour in wild white-handed gibbons (Hylobates lar)

Homosexual mounting in apes and prosimians is rare. Male-male mounting was observed between an adult male white-handed gibbon and an adolescent male in the same group. The behaviour is discussed in terms of the gibbon group's social structure and the development of the adolescent. It is suggested that this behaviour provides reassurance for the adolescent gibbon.     

云南元谋小河地区古猿地点的小型猿类化石

本文记述的云南元谋小河地区古猿地点发现的一种小型猿类。它的牙齿形态比晚中新世的禄丰粗壮池猿进步。而牙齿的某些形态介于粗壮池猿和现生长臂猿之间,它的发现为探讨现生长臂猿的起源与进货提供了新的化石依据。依哺乳动物群的初步研究,其时代稍晚于禄丰古猿地点的时代。鉴于它的形态特征和地史分布,作者将它订为一新属新种：进步滇猿Ｄｉａｎｏ ｐｉｔｈｅｃｕｓ ｐｒｏｇｒｅｓｓｕｓ ｇｅｎ．ｅｔ ｓｐ．ｎｏｖ。     

The yellow-cheeked gibbon (Hylobates gabriellae) in nam bai cat tien (southern vietnam) revisited

Data concerning the status, habitat, and vocalizations of yellow-cheeked crested gibbons (Hylobates gabriellae) were collected during a short field trip to the Nam Bai Cat Tien National Park (southern Vietnam). Nam Bai Cat Tien may be the southernmost locality where crested gibbons (i.e. theHylobates concolor group) still survive. Fewer songs were heard at Nam Bai Cat Tien National Park than at other crested gibbon sites visited by the author. At least two gibbon groups appear to have been greatly reduced in number since previous surveys in the park. There is some evidence that both the gibbon population and the gibbon habitat in Nam Bai Cat Tien are disturbed. The first case of a great call solo song in wild gibbons of theconcolor group is reported. Great calls ofH. gabriellae are described and documented with sonagrams for the first time. They differ from those previously described forH. leucogenys.     

利用染色体涂染方法建立人和白眉长臂猿(Hylobates hoolock)的比较染色体图谱

除人Y染色体外,本文采用生物素标记的人全部整条染色体特异探针与白眉长臂猿(Hylobates hoolock)有丝分裂中期分裂相进行染色体原位杂交即染色体涂染法以研究人和白眉长臂猿染色体之间的同源性。在白眉长臂猿18对常染色体上检测出了与人22对常染色体同源的59对染色体片段,确定了人和白眉长臂猿之间的精度较高的染色体连锁群。结果表明:自人与白眉长臂猿的祖先分歧以来,大量的染色体间重排(至少发生了39次易位)和染色体内的重排导致了二者核型的差异。根据杂交结果绘制了首份人和白眉长臂猿比较染色体图谱,并结合已有的人和白掌长臂猿(Hylobates lar)(2n=44)和合趾长臂猿(Hylobates syndactylus)(2n=50)的比较染色体图谱对长臂猿属的染色体进化作了初步的探讨。     

Lingual incisor traits in modern hominoids and an assessment of their utility for fossil hominoid taxonomy

The morphology of the anterior dentition has received scant attention for purposes of taxonomic discrimination. Recently, however, lingual incisor morphology was used in differentiating several Miocene ape species and genera. This paper assesses the utility of this morphology for taxonomic discrimination by examining the nature and patterns of variation in lingual incisor morphology in extensive samples of modern chimpanzees, gorillas, orangutans, and gibbons. This paper documents discrete morphological traits on the lingual side of incisors. Trait frequencies are used in univariate and multivariate analyses to examine the apportionment of variation in species, subspecies, and populations. A correlation between lingual incisor traits, tooth dimensions, and sex attempts to determine if such factors affect the manifestation of traits. Finally, the findings are applied to understanding patterns of variation in the Miocene hominids. The study demonstrates that: 1) lingual incisor morphology differs substantially between the hylobatids and great apes; 2) variation in incisor traits is high within species, and most of it is found within local populations; and 3) incisor traits do not correlate significantly with incisor dimensions or sex. Species and to some extent subspecies of extant hominoids can be differentiated statistically using lingual incisor traits, but the frequency of traits such as continuous or discontinuous cingulum, or the presence or absence of pillars, differentiates them. Given this pattern of variation, I argue that it is necessary to assume and document similar patterns of variation in Miocene apes before incisor morphology is used for differentiating taxa.     

Calling in wild silvery gibbons (Hylobates moloch) in Java (Indonesia): behavior, phylogeny, and conservation

Hardly any behavioral data are available for the silvery gibbon (Hylobates moloch), an endangered primate that is endemic to the island of Java, Indonesia. We studied the singing behavior of the easternmost population of this species in the Dieng mountains, central Java, in 1998-1999. We aimed to document the timing of singing, quantify the amount of singing by the respective sexes, and explore the role of bioacoustics in density estimation. A total of 122 song bouts in at least 12 groups were monitored. No duet songs were heard. Most of the song bouts (91.5%) were female solo song bouts or female scream bouts. In contrast to an earlier study on the westernmost population of silvery gibbons, during which few if any male songs were heard, at least 8.5% of the song bouts in our study were male solo song bouts. They were significantly longer in duration than the female songs. All male song bouts uttered before dawn (0520 hr) were produced in a chorus fashion, with at least three individuals participating. Choruses occurred about once every 8.5 days, and lasted longer and occurred earlier than female solo song bouts. Most male songs (60%) started between 0355-0440 hr, when it was still dark. All female songs, in contrast, started after 0500 hr, and female singing activity peaked around 0600. Regular male singing, male chorusing, and regular predawn singing have not previously been reported for silvery gibbons. Similarly separated periods of male and female solo songs and the absence of duetting have been observed in Kloss's gibbons (H. klossii) on the Mentawai Islands, and may represent synapomorphies shared by both species. The pronounced individual-specific song characteristics of silvery gibbons allow accurate mapping of groups. The density of gibbons at our study site was established to be 1.9-3.7 groups/km2, corresponding to 6.7-13.1 individuals/km2. We reassess the suitability of gibbon songs as a means of estimating the density and size of gibbon populations, and discuss the proximate causes for the absence of duetting in silvery gibbons.     

Food Preferences and Nutrient Composition in Captive White-handed Gibbons, <Emphasis Type="Italic">Hylobates lar</Emphasis>

We aimed to assess spontaneous food preferences in captive white-handed gibbons and to analyze whether they correlate with nutrient composition. Via a 2-alternative choice test, we repeatedly presented 3 male Hylobates lar with all possible binary combinations of 10 types of food that are part of their diet in captivity and found the following rank order of preference: grape > banana = fig > apple > pear > honeydew melon > carrot > tomato > cucumber > avocado. Correlational analyses revealed a highly significant positive correlation between the food preference ranking and the total carbohydrate, fructose, and glucose contents of the foods (p < 0.01, respectively). With the exception of the trace mineral selenium (p < 0.05), there was no other significant correlation with any other macro- or micronutrient. In addition, the food preferences were stable across the day because rankings obtained from tests performed at 0900, 1200, and 1500 h, respectively, did not differ significantly (p > 0.05). Our results suggest that captive white-handed gibbons are not opportunistic, but selective feeders with regard to maximizing net gain of energy because only the content of carbohydrates, but not the contents of total energy, proteins, or lipids significantly correlate with the displayed food preferences. Further, the results suggest that captive Hylobates lar, in contrast to their free-ranging conspecifics, do not display marked changes in their food selection across the day.     

Fighting between two females for a male in the hoolock gibbon

I observed fighting between two adult females for an adult male in a group of hoolock gibbons (Hylobates hoolock)during fieldwork conducted between November 1988 and December 1990 at Lawachara in the West Bhanugach Reserve Forest, Sylhet, Bangladesh. I discuss the history of the episodes and the consequences of fighting.     

Estimation of density of gibbon groups by use of loud songs

The density of gibbon populations may be estimated by listening for the loud duetted songs of monogamous territorial groups. This method requires a correction factor which must be estimated from the frequency of singing of an adequate number of known study groups. The correction factor and its error were estimated for pileated gibbons (Hylobates pileatus) in Khao Soi Dao Wildlife Sanctuary in southeastern Thailand. Among 30 groups studied, 47% sang per day, on average, but the variation between days and the variation in singing frequency between groups were large. Weather conditions, especially windiness, explained some variation in singing. During an area-wide survey of groups in the sanctuary, unexplained variation in singing from day to day accounted for approximately half of the sample error of group density estimated from 1-day listening samples. Error due to day-to-day variability can be reduced by listening for more than one day at each site. Correction factors based on the cumulative proportion of groups heard during longer (2–5-day) sample periods of listening were closer to 1.0, therefore leaving less room for error and bias of the correction factor. © 1993 Wiley-Liss, Inc.