American Journal of Primatology最新文献

Chimpanzees form social communities with memberships that change only with births, deaths, and female emigrations or immigrations and that are characterized by high fission-fusion dynamics. Relations between neighboring communities are intensely hostile, and males in the same community cooperate in potentially lethal intercommunity aggression. Permanent community fissions sometimes occur, but genetic data indicate that these are rare, and only a single case, from Gombe, had been known until recently. The unusually large Ngogo chimpanzee community in Kibale National Park, Uganda, observed continuously since 1995, underwent a gradual permanent fission during the 2010s that culminated in the inception of lethal intercommunity aggression in 2018. Males at Ngogo could be assigned to different socio-spatial neighborhoods based on association data before the permanent fission, but data on characteristics of grooming networks show that all belonged to a single community until around 2011. Subsequently, grooming networks showed clear differentiation between what became the Ngogo Central and Ngogo West communities. This preceded the first obvious behavioral signs of permanent fission. In principle, a model developed by Sueur et al. (2011; cf. Sueur and Maire 2014) to explain how increases in group size in papionin primates could lead to fracturing of female grooming networks and facilitate permanent fissions should apply to male chimpanzees, given the importance of male-male grooming for maintaining social bonds and cooperation in intergroup aggression. However, analysis of long-term data on male-male grooming indicates that increases in the number of females at Ngogo and variation in their residence decisions apparently had a greater effect on the dissolution of a community-wide male grooming network than did increases in the number of males. These results support the hypothesis that the main drover of the permanent fission was male reproductive competition, not constraints on the ability of males to maintain grooming networks.

Demographic analysis is often used for the effective management of wildlife, especially for species facing human-caused disturbances to their habitat, such as habitat fragmentation. The objective of this long-term study was, therefore, to gain insights into the status of a lion-tailed macaque (Macaca silenus) population, inhabiting the Puthuthottam estate near Valparai in the Western Ghats of southwestern India, by documenting demographic factors, such as group numbers, group size and age/sex composition, as well as estimating growth, birth, and mortality rates. We documented the demography of five resident groups of this species, comprising 5% of the remaining wild lion-tailed macaque populations. In this paper, we present a demographic history of the Puthuthottam population through comparisons with studies conducted by various research groups, beginning in the 1970s, and report a five-fold increase in population size over a period of four decades. Using Generalized Linear Mixed Models, we analyze and discuss the effects of population demographic parameters on birth rates, including a moderately reduced growth- and birth rate, as compared to previous records for the population. The most frequent contributor to mortality, especially of the vulnerable juvenile age class, was found to be roadkill deaths, followed by other anthropogenic causes, including electrocution on exposed electric lines. We also report a shift in the social system, pervasive across this population, from unimale–multifemale to multimale–multifemale social groups. We strongly believe that the observed drastic alterations to the socioecological profile of the study population, as a result of habitat fragmentation and increased utilization of human habitats, have major implications for the long-term survivability of this macaque population. We hope the information presented in this paper will aid in the effective management of the remaining lion-tailed macaque populations across their distribution range, particularly as they become increasingly exposed to human-altered habitats.

Howler monkeys are considered high-quality seed dispersers; however, the changes that seeds undergo after passing through their digestive tract, which influence their germination capacity, are still unknown. In this study, we assessed whether the consumption of seeds from three species of the Moraceae family by mantled howler monkeys results in seed coat scarification, and whether this treatment enhances their permeability to water and germination rate. Using seeds from fruits, we induced chemical scarification of their outer coat, and with these, intact seeds and seeds found in droppings, we conducted micromorphological analyses, water permeability tests and germination assays. We observed that the passage of seeds through the digestive tract of mantled howler monkeys did not scarify their outer coat, nor did it enhance their water absorption capacity. There was both a positive and negative effect on the germination of Ficus americana and Ficus insipida seeds, respectively. Chemical scarification of the seeds, although it reduced their coat thickness, did not increase water permeability, significantly decreased their viability, and prevented germination. These results suggest that, in the case of small seeds, scarification is not a relevant treatment for germination and may, in fact, be unfavorable. Therefore, the importance of seed consumption by mantled howler monkeys, and other frugivores, may lie in the removal of pulp in terms of the facilitation of germination. Thus, by moving, releasing and cleaning the seeds, these animals may increase the probability that they will encounter adequate environmental conditions for germination and establishment.

Vocal signals are the primary means of communication for most nonhuman primates. Quantitatively describing the vocal repertoire of specific species at specific age stages is a crucial step in studying their vocal communication, and it also provides a foundation for understanding the development and use of primate vocal signals. This study is the first attempt to establish a vocal repertoire for wild infant Tibetan macaques based on quantitative methods. We conducted continuous 5-month tracking observations on 18 wild Tibetan macaques aged 0–24 months living in the Yulinkeng A1 group (YA1 group) of the Wild Monkey Valley in Huangshan, collecting a total of 6667 vocal samples and defining common vocalization contexts in 8 categories. Through the quantitative analysis of 41 main acoustic parameters in 557 high-quality samples, we ultimately identified 10 call types (coo, loud coo, modulated tonal scream, whistle, bark, three-syllable chuck, rattle, squeal, noisy scream, and undulated scream). Four call types (three-syllable chuck, squeal, noisy scream, and undulated scream) were no longer used as the monkeys reached 14 months of age. Compared with adult individuals, there are three specific call types in the infant stage (three-syllable chuck, rattle, and undulated scream). Additionally, the vocalizations we collected from infant and yearling monkeys were mainly related to their communication with their mothers. Our study fills a gap in knowledge of the vocal behaviors of Tibetan macaques, particularly those of infants, and provides foundational data for the study of vocal development in Tibetan macaques. It also offers new perspectives on the evolution of primate vocal communication.

Goeldi's monkey (Callimico goeldii, the lone species in this genus) shows an array of characteristics that are typical for both New World primate families, the Cebidae and the Callitrichidae, and as such their taxonomic classification has remained in question. Based on DNA, the genus Callimico is regarded as a member of the monophyletic group of clawed New World monkeys (Callitrichidae). Callitrichids, as a rule, give birth to twins, which are blood chimeras due to placental blood vessel anastomoses. In contrast, wild and captive Callimico almost exclusively have singleton births, as in all cebids. To address whether Callimico shares chimeric twinning with other callitrichids, we did DNA profiling of the only presently available twin pair of captive Callimico. DNA banding patterns revealed distinct differences between the twins, indicating an absence of blood chimerism. We infer that predominantly single birth in Callimico most likely represents a derived state that evolved independently in this genus, rather than the ancestral callitrichid condition.