Wild Long-tailed Macaques Research Articles

Social and Genetic Aspects of Paternity in Wild Long-Tailed Macaques (Macaca Fascicularis)

AbstractIn a field study of three groups of wild long-tailed macaques, Macaca fascicularis, observations on social behaviour could be related to genetically determined paternity. In contrast to what has been found in many previous studies on captive primate groups, we found a relatively strong correlation between male dominance rank and reproductive success. In a large group the high success of the alpha male compared to other males could be explained only partly by his higher copulation score. His success also resulted partly from better timing of his copulations during maximum fertility of the females, in comparison with other males. We must conclude either that the alpha-male has more access to fertile females, or that females have a preference for the alpha-male during their maximum fertility. The females clearly displayed promiscuous behaviour. This behaviour implies a risk to a female that a male other than the alpha-male with proven qualities will become the father of her offspring. One expects that there must be a social advantage related to this female strategy. In the absence of indications of any direct social advantages to the female of this sexual behaviour pattern, the ultimate explanation for this female promiscuity is most likely is aggression reduction. This could be either through the devaluating of any single copulation, or through the confusion of paternity and a resultant reduction in the risk of infanticide.

Male dominance rank and reproductive success in primate groups

The relationship between male dominance rank and reproductive success has been a topic of interest since the beginning of primatology. From a theoretical point of view the existence or absence of this relationship has great implications with respect to the meaning of dominance rank and more general of the social relationships between individuals within social groups. Until fairly recently mating behaviour has been used as an indicator of reproductive success, but these two variables need not be correlated. The relations between mating success, reproductive success, and dominance rank indicate whether selective mating is involved (different mating partners at different phases of fertility, for example through male contest or female choice). With the development of genetic techniques to determine reproductive success directly, it has now become possible to investigate these relations. In our study on wild long-tailed macaques (Macaca fascicularis) we find a relatively strong correlation between rank and reproductive success which is attributable to selective mating by the alpha male during fertile periods of the females. In most previous studies no such clear results have been obtained, and we discuss the differences in outcome in relation to the study conditions, group sizes, and possible differences between species in terms of reproductive strategies.

Post-conflict behaviour among wild long-tailed macaques (Macaca fascicularis)

A procedure originally developed for the study of post-conflict behaviour in captive groups was used to study a group of long-tailed macaques (Macaca fascicularis) in the wild. During 5 months, 156 post-conflict observations on victims of agonistic conflicts were collected and compared with matched-control observations. The findings reported previously for a captive group of the same species were confirmed. After a conflict victims scratched themselves more often and received more attacks than in control periods. Reconciliation and redirection were found to be characteristic of post-conflict situations. Their occurrence seemed to follow similar patterns in captivity and in the wild. The frequency of reconciliation, but not that of redirection, seemed to be lower after conflicts over food than in other situations. No evidence for consolation was found. In the wild, victims have the option of leaving the (sub)group in order to avoid the former aggressor. No evidence for this behaviour was actually found, but within the (sub)group victims tended to keep the former aggressor at a distance. Victims also seemed to suffer ecological costs in that they spent less time foraging than in control periods.

A preliminary study of vocal communication in wild long-tailed macaques (Macaca fascicularis). I. Vocal repertoire and call emission

Vocal communication in wild long-tailed macaques (Macaca fascicularis) is described in terms of (1) a preliminary vocal repertoire and the situations in which calls occur in the natural habitat of this species and (2) quantitative measurement of the natural occurrence of calls in the field. Although a number of calls are relatively discrete (e.g., a male loud call), gradation is pronounced for both wide-spectrum (“harsh”) and narrow-spectrum (“clear”) vocal signals. Thirteen general types of harsh calls are identified provisionally as elements of the vocal repertoire. The exact number of discrete clear calls contributing to the vocal repertoire could not be ascertained precisely, but these calls were classified operationally into six broadly acoustically different classes in order to measure natural vocal behavior. Vocalizations tended to occur in temporal “clusters” during sample, periods. Narrow-band clear or “coo” calls were more frequently performed by macaques than wide-band harsh calls. The possible functional implications of the correlated occurrence of multiple vocal signals are discussed.

A preliminary study of vocal communication in wild long-tailed macaques (Macaca fascicularis). II. Potential of calls to regulate intragroup spacing

This study is a preliminary assessment of the potential of long-tailed macaque (Macaca fascicularis) calls to operate in systems of within-group spacing. Covariation in the rate of occurrence of calls with party spread, size, and activity among wild individuals of one group suggested that four classes of calls may function in intragroup spacing. Two of them are “clear” calls of long duration and pronounced frequency modulation. Calling rate increased with party spread for low- and high-frequency variants of these calls during resting and feeding respectively, suggesting possible utility in maintenance of spatial relations over moderately long distances. A third “harsh” call was negatively correlated with party spread during foraging and may thus function to increase dispersion among foraging individuals. Another harsh call with a tonal onset was unique among all calls in the vocal repertoire in being more frequently performed by lone, isolated individuals than by macaques accompanied by others, suggesting a possible function in reestablishing contact that has been severed. The functional significance of these calls with respect to their acoustic structures is discussed. Macaques that use calls to regulate intragroup spacing can control communication distance and direction by their choice of acoustically different vocalizations. This choice may be affected not only by varying environmental constraints on sound transmission, but also by social and ecological factors such as intragroup competition.

Wild long-tailed macaques (Macaca fascicularis) in Thailand are highly infected with gamma herpes virus but not with simian T-lymphotropic retrovirus of type 1.

Wild long-tailed macaques (Macaca fascicularis) in Thailand are highly infected with gamma herpes virus but not with simian T-lymphotropic retrovirus of type 1.

A pilot study of the social correlates of levels of urinary cortisol, prolactin, and testosterone in wild long-tailed macaques (Macaca fascicularis)

Urine samples were collected from individuals in a wild population of Sumatran long-tailed macaques (Macaca fascicularis), and the levels of cortisol, immunoreactive prolactin, and (for males) testosterone were determined. The amount of foraging during the 2 hr preceding urine collection were found to affect the levels of urinary cortisol, but not those of the other hormones. Immigration into a new group and having one's infant kidnapped led to increased levels of cortisol. Levels of cortisol and testosterone were correlated both within and between individuals, whereas prolactin varied independently. The effects of age, reproductive status, and social rank on the mean values of individuals were also examined. Lactating females had higher prolactin levels than non-lactating ones; reproductive state interacted with the age effect on prolactin and possibly cortisol. No effects of social status were found in spite of a small, but consistent effect of rank on birth rate in this population. Among males, age and rank are strongly linked. The low ranking old males had increased levels of cortisol, even though the younger high-ranking males were involved in the fiercest conflicts.

Changes in the Behaviour of Wild Long-Tailed Macaques (Macaca fascicularis) after Encounters with a Model Python

Changes in the Behaviour of Wild Long-Tailed Macaques (Macaca fascicularis) after Encounters with a Model Python

The Effect of Some Non-Social Factors On Mother-Infant Contact in Long-Tailed Macaques (Macaca Fascicularis)

Mother-infant dyads were studied among wild long-tailed macaques in North Sumatra (Indonesia). The influence of arboreality and mother's immediate activity on physical contact was examined during the first 5 months of infant life. Both factors were found to be contingent on the contact probability. It was suggested that mother long-tailed macaques might intensify protective behaviour when staying high in the canopy to prevent the infant from falling. Though mothers were very rarely observed rejecting their infants, the infants seemed to learn that they could be in or out of contact a particular times depending on their mother's activity. The development of this relationship is suggested to be based upon economical principles.

Male migration and rank acquisition in wild long-tailed macaques ( Macaca fascicularis)

In a 3-year study of a wild population of long-tailed macaques ( Macaca fascicularis), 52 male migrations from and into six study groups were observed. Two hypotheses derived from the literature were confirmed: (1) younger males immigrate more often into adjacent groups than older males, who immigrate more often into groups further away; and (2) younger males migrate more often together with group-mates than older males do. Two types of immigrants were distinguished: ‘unobtrusive’ and ‘bluff’. The unobtrusive immigrants entered low in the male dominance hierarchy and were males of all age classes, whereas the bluff immigrants attempted to take over the highest dominance rank of their new group and were all young adult males. Take-overs of dominance were also attempted by resident young males who had just reached full adulthood during a period of semi-solitariness. They behaved in a way similar to the bluff immigrants but were more successful than the bluff immigrants, who only succeeded in taking over small groups. The results indicate that knowing the other resident males might be the most important determinant of take-over success in multi-male groups.

The effect of group size on time budgets and social behaviour in wild long-tailed macaques (Macaca fascicularis)

A comparison of data on ranging, activity budgets and frequencies of social behaviour gathered over a range of group sizes for an omnivorous, forest-living monkey, the long-tailed macaque (Macaca fascicularis), showed that the length of the day journey, the time spent travelling and searching for dispersed food items, as well as social tension, show a monotonic increase with group size. A behavioural mechanism behind these patterns is the “puhing forward” effect: foraging animals tend to move away when approached by others, presumably because they reduce the availability of dispersed food items in patches they have searched. By avoiding being overtaken animals are not forced to search in depleted patches. An alternative mechanism, the limited capacity of fruit trees, does not operate in the present case. It is concluded that theories postulating feeding advantages to be the primary factor favouring group living do not apply in this case.