Confirmation and location of the hybrid zone between wild populations of Macaca tonkeana and Macaca hecki in Central Sulawesi,Indonesia

Reports of hybridization between Macaca tonkeana and Macaca hecki were investigated in Central Sulawesi, Indonesia. We defined sets of morphological traits that were diagnostic for M. tonkeana and M. hecki and then located an areas where animals had intermediate or mosaic features. Hybridization as indicated by morphology was detected between M. tonkeana and M. hecki. The hybrid zone appeared to be strongly centered at the road that crosses the isthmus of Central Sulawesi from Tawaeli to Toboli. Macaques in this region were not morphologically uniform; animals from the western area of the Tawaeli–Toboli road resembled M. hecki, while animals from the eastern area resembled M. tonkeana. The hybrid zone was found to be smaller than previously thought, with maximum dimensions of approximately 15 and 7.5 km. Clines for diagnostic morphological features were broadly coincident, suggesting that the hybrid zone originated by secondary contact. Analysis of three museum specimens collected in 1916 provided evidence that the hybrid zone has been in existence since at least then. The narrow width of the hybrid zone, along with its age, suggested that some prezygotic or postzygotic barrier must exist to full introgression between M. tonkeana and M. hecki. Am. J. Primatol. 43:181–209, 1997. © 1997 Wiley-Liss, Inc.     

Population densities of Sulawesi crested black macaques (Macaca nigra) on Bacan and Sulawesi,Indonesia: Effects of habitat disturbance and hunting

Population surveys of Sulawesi crested black macaques (Macaca nigra) were conducted on the Indonesian islands of Sulawesi and Bacan in 1992–1994 to assess the status of natural populations and determine habitat and anthropogenic factors affecting their population densities. We surveyed five sites for primates, including undisturbed and disturbed habitats. Data were collected on habitat structure and composition at two undisturbed and one disturbed forest site in which the primates were surveyed. The highest density of macaques was found in primary forest at Gunung Sibela Nature Reserve on Bacan (170.3 individuals/km²). Population density in logged forest on Bacan was high but significantly less than primary forest (133.4 individuals/km²). The high density of crested black macaques in primary forest on Bacan is best explained by the high carrying capacity found in primary forest. The lower food quantity and quality of food resources found in logged forest correlated with lower primate densities compared to primary forest. However, the large population of macaques in logged forest demonstrates the conservation value of such forest. Densities on Sulawesi at Tangkoko-Batuangas-DuaSudara Nature Reserve (TBDS) showed a continuing decline since earlier surveys. Primate densities were highest near the protected center of Tangkoko Reserve (66.7 individuals/km²). The peripheral areas of Batuangas and DuaSudara, even though adjacent and continuous, showed lower population densities of 46.4 and 23.5 individuals/km², respectively. The best explanation for the continued decline of Macaca nigra populations at TBDS is hunting. Unless conservation measures are implemented immediately, M. nigra on Sulawesi risks extinction in the near future. Am. J. Primatol. 44:89–106, 1998. © 1998 Wiley-Liss, Inc.     

Group composition,home range,and diet of the maroon leaf monkey (Presbytis rubicunda) at Tanjung Puting Reserve,Central Kalimantan,Indonesia

Maroon leaf monkeys (Presbytis rubicunda) were studied at the Orangutan Research Conservation Project study area at the Tanjung Puting Reserve in Central Indonesian Borneo for approximately 15 months in 1974, 1975, and 1977. Over 250 observation hr involving 300 encounters with the monkeys were logged. Troop size ranged from three to eight individuals in the nine troops surveyed with only one adult male being present in each troop. Home range size varied from 0.33 km² to 0.99 km² and correlated with troop size. Forty-six different food types were observed eaten by the maroon leaf monkeys; of these foods, 52% consisted of fruits, 36% of leaves, and 12% of flowers.     

Growth and sexual dimorphism in a population of hybrid macaques

Growth and sexual dimorphism have long been the focus of investigation for researchers interested in the life history and socioecology of nonhuman primates. Previous research has shown that sex differences in the duration of growth, or bimaturism, are primarily responsible for the sexual dimorphism observed in anthropoid primates with multimale–multifemale social structure, such as macaques. The present study investigates sex differences in patterns of craniofacial and somatometric growth relative to head and body size and relative to dental development in a population of hybrid macaques (Cercopithecidae: Macaca ) from Sulawesi, Indonesia. How these patterns may contribute to sexual dimorphism in this hybrid population is also examined. The results of the study suggest that there is no substantial effect on the levels of sexual dimorphism associated with hybridization in these macaques. Although sex differences in patterns of size-related, or allometric, growth patterns play a significant role in the development of sexual dimorphism for some cranial dimensions in these hybrids, bimaturism seems to be the primary component in the ontogeny of sexual dimorphism in this hybrid population. The observed levels of hybrid dimorphism and the predominant ontogenetic pattern of bimaturism characterized by prolonged male growth are consistent with previously published reports on dimorphism and growth in other cercopithecine primates.     

Diversification of Sulawesi macaque monkeys: decoupled evolution of mitochondrial and autosomal DNA

Abstract. In macaque monkeys, females are philopatric and males are obligate dispersers. This social system is expected to differently affect evolution of genetic elements depending on their mode of inheritance. Because of this, the geographic structure of molecular variation may differ considerably in mitochondrial DNA (mtDNA) and in autosomal DNA (aDNA) in the same individuals, even though these genomes are partially co-inherited. On the Indonesian island of Sulawesi, macaque monkeys underwent an explosive diversification as a result of range fragmentation. Today, barriers to dispersal have receded and fertile hybrid individuals can be found at contact zones between parapatric species. In this study, we examine the impact of range fragmentation on Sulawesi macaque mtDNA and aDNA by comparing evolution, phylogeography, and population subdivision of each genome. Our results suggest that mtDNA is paraphyletic in some species, and that mtDNA phylogeography is largely consistent with a pattern of isolation by distance. Autosomal DNA, however, is suggestive of fragmentation, in that interspecific differentiation across most contact zones is significant but intraspecific differentiation between contact zones is not. Furthermore, in mtDNA, most molecular variation is partitioned between populations within species but in aDNA most variation is partitioned within populations. That mtDNA has a different geographic structure than aDNA (and morphology) in these primates is a probable consequence of (1) a high level of ancestral polymorphism in mtDNA, (2) differences between patterns of ancestral dispersal of matrilines and contemporary dispersal of males, and (3) the fact that female philopatry impedes gene flow of macaque mtDNA.     

Hybridization and population genetics of two macaque species in Sulawesi, Indonesia

This study investigates hybridization and population genetics of two species of macaque monkey in Sulawesi, Indonesia, using molecular markers from mitochondrial, autosomal, and Y-chromosome DNA. Hybridization is the interbreeding of individuals from different parental taxa that are distinguishable by one or more heritable characteristics. Because hybridization can affect population structure of the parental taxa, it is an important consideration for conservation management. On the Indonesian island of Sulawesi an explosive diversification of macaques has occurred; seven of 19 species in the genus Macaca live on this island. The contact zone of the subjects of this study, M. maura and M. tonkeana, is located at the base of the southwestern peninsula of Sulawesi. Land conversion in Sulawesi is occurring at an alarming pace; currently two species of Sulawesi macaque, one of which is M. maura, are classified as endangered species. Results of this study indicate that hybridization among M. maura and M. tonkeana has led to different distributions of molecular variation in mitochondrial DNA and nuclear DNA in the contact zone; mitochondrial DNA shows a sharp transition from M. maura to M. tonkeana haplotypes, but nuclear DNA from the parental taxa is homogenized in a narrow hybrid zone. Similarly, within M. maura divergent mitochondrial DNA haplotypes are geographically structured but population subdivision in the nuclear genome is low or absent. In M. tonkeana, mitochondrial DNA haplotypes are geographically structured and a high level of nuclear DNA population subdivision is present in this species. These results are largely consistent with a macaque behavioral paradigm of female philopatry and obligate male dispersal, suggest that introgression between M. maura and M. tonkeana is restricted to the hybrid zone, and delineate one conservation management unit in M. maura and at least two in M. tonkeana.     

Population survey of macaques in northern Sulawesi

A field survey of 25 sites in Sulawesi Utara (north Sulawesi) in 1987 and 1988 found macaques in 16 of these sites. The most viable population of Macaca nigra was found in the Tangkoko reserve at an estimated density of 76.2 monkeys/km², which is less than one-third the abundance reported in the late 1970s by the MacKinnons. The adjacent reserves of Batuangus and Duasudara had only 22 monkeys/km², yielding a population estimate for these three contiguous reserves of only 3,655 individuals. Maccaca nigrescens were found in the central and western portions of Dumoga-Bone National Park in densities of 15.5 and 16.4 monkeys/km², significantly below the density of 27/km² reported by the MacKinnons. The more peripheral areas of Dumoga-Bone had only 8.15 monkeys/km², yielding a population estimate of M. nigrescens in Dumoga-Bone of less than 34,000. Our total population estimate for M. nigra and M. nigrescens combined is less than 50,000 individuals, which is considerably below that reported in recent litreture. M. hecki were observed in only two locations, Tangale and Panua Reserves, at low densities of 3.3 to 5.2 monkeys/km², suggesting its range and abundance have declined since the observations of Groves (pp. 84–124 in THE MACAQUES: STUDIES IN ECOLOGY, BEHAVIOR AND EVOLUTION. D. G. Lindburg, ed. New York, Van Nostrand Reinhold, 1980). Several factors have contributed to population decline in these species: habitat shrinkage, increasing human population pressure, and drought conditions. Group sizes were significantly smaller in our study than in previous ones, and we found a shortage of juveniles and infants.