Experimental field study of the relative costs and benefits to wild tamarins (Saguinus imperator and S. fuscicollis) of exploiting contestable food patches as single- and mixed-species troops

Several species of tamarins form stable mixed-species troops in which groups of each species feed, forage, rest, and travel together during much of the year. Although the precise set of factors that facilitate this ecological relationship remains unclear, predator detection and foraging benefits are presumed to play a critical role in maintaining troop stability. In this work we present data from an experimental field study designed to examine how factors such as social dominance and within-patch foraging decisions affect the costs and benefits to tamarins of visiting feeding sites as single- and mixed-species troops. Our data indicate that when they exploited contestable food patches (sets of eight feeding platforms, two of which contained a 100-g banana), each tamarin species experienced foraging costs when they arrived as part of a mixed-species troop. These costs were found to be less severe for emperor tamarins because they were socially dominant to saddle-back tamarins and could displace them at feeding sites. We conclude that the foraging benefits to tamarins residing in mixed-species troops are asymmetrical, and that at feeding sites in which the amount of food in a patch is insufficient to satiate all troop members, even minor differences in the timing of return to food patches and changes in troop cohesion have a measurable effect on the costs and benefits to participating tamarin species.     

Solitary male chacma baboons in a desert canyon

Solitary and paired adult (nine) and subadult (one) male chacma baboons, Papio ursinus, were observed over a period of years living in part of a wooded desert canyon not used by adjacent troops. These extratroop males were silent when alone and gave only one alarm vocalization, the “wa-hoo” call, when paired. The space occupied by them is unsuitable for use by troops according to criteria for adequate sleeping sites and access to water. But the foods available to them, especially figs, but also other fruits and fresh acacia seeds, were abundant. These foods are more highly preferred by baboons than those foods available to troop members. Troop members deplete these resources and shift to less preferred foods with lower water content and longer processing times. All of the adult members of the troop adjacent to these isolated males were infected with a skin disease. Isolated males were not so afflicted and so cannot have originated from, or ever been a part of, this troop. They probably moved to the space where they were observed from other inland troops, traveling to their current home range along the narrow canyon river course.     

Intertroop relationships among Japanese monkeys

Intertroop relationships among Japanese monkeys, which have been paid only scant attention for the past 20 years, are examined from several points of view. Japanese monkey troops are generally distributed in such a way as to concentrate locally, that is, to form a local concentration of troops (LCT). About 20% of the nomadic ranges of the troops within LCT's overlap; but in their natural state, they seldom approach but rather to avoid one another. From observations of intertroop encounters at Takasakiyama, where three troops are provisionized and use the same feeding place, it has been found that there exists a dominant-subordinate relationship among troops, that monkeys of each troop have a clear consciousness of belonging to their troop, and that monkeys of different troops rate one another on the basis of their capability. The frequency of male transfer between troops within LCT's is by far higher than between LCT's. In Japanese monkey society, a troop only is a social unit and a social order higher than a troop is not seen; however, it is not impossible to consider an LCT a consanguineally connected group by reason of the transfer of males among the troops within it.     

Intra-troop affiliative relationships of females with newborn infants in wild ring-tailed lemurs (Lemur catta)

To determine how the birth and development of infants influence their mothers' social relationships with other adult troop members, we observed two free-ranging troops of ring-tailed lemurs (Lemur catta) at the Berenty Reserve, Madagascar. The number of acts of affiliative contact that the mothers received from other adult troop members during the first and second months of infant life were significantly higher than those before they gave birth, and the values during the third month were as low as that before giving birth. Two mothers received acts of affiliative contact less frequently after their infants died, compared with the values while the infants were alive. On the other hand, more than 95% of all acts of licking of infants by adult troop members other than their mothers occurred when the infants were in contact with their mothers. These findings suggest that infants per se and mothers per se were not attractive, but rather the mother-infant pair was attractive to other troop members. Acts of infant-licking were observed in almost all mother-mother pairs and mother-non-mother adult female pairs, and in two thirds of mother-adult male pairs. Moreover, the frequency of infant-licking was not affected by female parity, female and male dominance rank, or infant sex. Therefore, acts of infant-licking, which are widespread among troop members, may function to make or maintain stable social relationships.     

Changes in dominance rank and division of a wild Japanese monkey troop in Arashiyama

This article forms the second report on the Arashiyama troop of Japanese monkeys and concerns a troop division which took place in June, 1966, and various problems of rank and consanguinity which accelerated the division. (1) The hypothesis advanced in the first report has been verified; (2) at the time of troop division, several consanguineal groups formed one unit; (3) among 16 consanguineal groups, those from 1st to 7th in rank joined the A troop, while those from 8th to 16th joined the B troop; (4) dominance relation between the two division troops was B troop>A troop, reflecting the former ranking between the leader males of the two troops; (5) shifting of monkeys from one troop to the other after division occurred frequently, but males began to make their own movements when they attained 4 or 5 years of age and rarely moved together with their mothers or other consanguineous-relatives; (6) monkeys which were continuously in the same troop after division almost always obtained higher ranks than did monkeys who frequently shifted from one troop to the other; (7) after division, some males joined neither of the two division troops but formed a group, a so-called all-male group or male party, and moved about independently.     

Troop-specific responses to long calls of isolated tamarins (Saguinus mystax)

Recently captured moustached tamarins (Saguinus mystax) were briefly separated from other members of their troop. Most separated animals emitted long calls that were, in general, similar in acoustic structure to those of sympatric tamarin species while retaining species distinctiveness. Individual differences also appeared in call structure. The long calls of a separated animal were responded to almost entirely by members of the animal's own troop rather than by other troops, and reciprocal calling occurred among troop members significantly more often than expected by chance. Although there was no evidence of troop-specific call structure or dialect, there were troop-specific responses to the calls of separated tamarins. This response implies the existence of a stable and integrated troop structure that allows troop members to learn and to respond to the individual specific features of each troop member's calls.     

Radio tracking of a male Japanese macaque emigrated from its group

A male Japanese macaque's ranging behavior before and after emigration from its group was investigated by using radiotelemetry techniques. The male's locations before leaving the troop were regarded as those of the troop, while those after leaving were regarded as those of a solitary male. Monthly home range sizes of the male with the troop were larger than those of the male moving alone, while the whole home range of the male with the troop for three months was much smaller than that of the male moving alone for five months. Overlaps between the male's home ranges with the troop between months were much greater than those between the ranges of the male moving alone. One neighboring troop's home range overlapped the male's range in August and September, and another neighboring troop's range overlapped the male's in October. The mean travel distance and speed of the male with the troop per day did not differ significantly from those of the male moving alone. The results suggest that emigrated males of Japanese macaques may visit home ranges of some troops and stay for a while without interacting troop monkeys before they decide to visit or join the troops.     

Social interactions among adult male langurs (Presbytis entellus) at Rajaji Wildlife Sanctuary

A population of langurs (Presbytis entellus)at the Rajaji Wildlife Sanctuary in northern India was investigated for 1820 hr throughout a 10-month period in 1978. Data were collected from four bisexual troops and the adult males that ranged outside of bisexual troops. Most (60%) of the observation hours occurred with a main study troop from which social and ecological data were collected. The langur population at Rajaji shows pronounced birth and mating seasons. The population density is high (ca. 80/km ²), with about 75% of the adult males living outside of bisexual troops, which typically are large and multimale. Males outside of bisexual troops occur in small all-male bands or as isolates. Relations between bisexual troops and all-male bands are characterized by relatively low levels of aggression, and members of all-male bands are able to associate with bisexual troops for prolonged periods during the mating season. As a result of these associations, nontroop males are about as successful as troop males in achieving reproductive access to troop females. These associations between bisexual troops and all-male bands occurred with a minimal amount of agonistic behavior and without mortality or injury to troop females or immatures.     

Movement patterns of yellow baboons (Papio cynocephalus): Central positioning of walking infants

According to DeVore and Washburn's protection theory of the spatial organization of moving baboon troops, walking infants, which are among the most vulnerable and least self-sufficient of all troop members, should tend to occupy the troop's center. The protection theory is an ultimate hypothesis from which persistently recurring behavior is expected. Two troops living in Mikumi National Park, Tanzania, were compared with troops studied at other locations. Walking infants tended to occupy the center of their troop and to be underrepresented primarily in the frontal portion of progressions and secondarily in the rear. The lead position of progressions was analyzed using 82 walking infants, 11 troops, three locations, two species, and three studies involving eight or more observers employing somewhat different procedures at the different study sites. Despite so many opportunities for variation, 1,317 observations from these 11 troops did not produce a single instance in which a walking infant led the troop and very few in which one was in the frontal twelfth.     

Habitual fission-fusion and social organization of the Hakone troop T of Japanese macaques in Kanagawa prefecture,Japan

To analyze the socioecological factors of habitual fission-fusion of troop members, which is an underreported phenomenon in Japanese macaques, the seasonal pattern of fission-fusion within the Hakone troop T in Kanagawa Prefecture, Japan, was examined. Although almost all the study troop members were included in a large-sized group in winter, a portion of its members of ten formed small subgroups from spring to autumn. The frequencies and age-sex composition of these subgroups changed seasonally. All troop members participated, more or less, in subgroup formation. Subgroups tended to be composed of animals of the same age-sex class. Troop members did not fission along matrilineal lines. Although the study troop members repeatedly joined with and parted from subgroups, the characteristic social structure of Japanese macaque troops was maintained. Habitual fission-fusion among troop members may be one of a number of foraging strategies that facilitate efficient food gathering when the population density exceeds and /or reaches the carrying capacity of the area. The seasonal variation of pattern and composition type of each subgroup could be attributed to alternation of attractive food plant species, as well as age, rank, and sexual activity of both sexes.     

Gm and Inv studies on baboons, Papio cynocephalus: analysis of serum samples from Kenya, Ethiopia and South Africa.

Serum samples from 526 baboons (Papio cynocephalus) from 10 troops from the Laikipia district of northern Kenya, from 60 baboons from two troops from the Awash National Park, central Ethiopia, and from 127 baboons from South Africa were tested for Gm and Inv allotypes. Four of the 10 troops from Kenya formed a western cluster and six formed an eastern cluster. The clusters were separated by approximately 10 miles. The samples were tested for Gm (1, 2, 3, 5, 6, 11, 13, 14, 15, 16, 17, 21, 24) and for Inv (1, 2, 3). All samples were negative for Gm (2, 6, 14, 16, 24). All from Kenya and Ethiopia were negative for Inv (2), and all were positive for Gm (11, 17) and for Inv (3). The south African samples differed from the others in that 10 were negative for Gm (11) and four were positive for Inv (2). Taking all animals into account, polymorphism was present for Gm (1, 3, 5, 11, 13, 15, 21) and for Inv (1, 2). No two Kenya troops had the same array of phenotypes or of haplotypes, but the four western troops were more similar to each other than to the six eastern troops. Three haplotypes were present in the eastern troops that were not present in the western troops and five were present in the western troops that were not present in the eastern troops. Five haplotypes appeared in at least some troops of each cluster of troops. The samples from each of the two troops from Ethiopia show the same three phenotypes but with significantly different frequencies. It is suggested that the variation in haplotype frequencies observed among the 10 troops from Kenya is the result of a founder effect deriving largely from fission of a large troop into two smaller troops. The data show that speculations about the evolutionary origin of the allotypes are premature. For most species, too few animals have been tested and except for those in this study their origins are not known. Finally, the samples have been from too restricted an area.     

Who is Responsible for Fission in a Free-ranging Troop of Baboons?

The study troop of chacma baboons (Papio cynocephalus ursinus) at Mkuzi Game Reserve, Zululand, South-Africa, comprised of about 76 members that split into two new troops. The events leading to this troop fission will be described and its possible causes will be discussed. Troop fission among baboons is generally attributed to the withdrawal of low-ranking females from the main group, as a result of the cost of food competition and its effect on their reproductive success. At Mkuzi, no evidence for food competition among females was recorded in terms of rank-related time spent feeding or other time—budget components, feeding-bout length, diet composition or context of female aggression. Moreover, no evidence for rank-related differential reproductive success was found in terms of inter-birth intervals or infant survival. Female mortality was, however, related to dominance rank, with circumstantial evidence suggesting that cause of mortality was predation by leopards. Rate of female disappearances, aggression levels among females, and the percentage of time they spent in proximity to other adult troop members increased after fission. Relatively short inter-birth intervals and extremely low infant mortality rate at Mkuzi resulted in a small number of receptive females at any one time, and therefore in high costs of male sexual competition as expressed in the high levels of male aggression and woundings, both reduced after fission. It is suggested that this troop fission may have been initiated by the resident males, triggered by the high cost of sexual competition, and forced on the females, who were, consequently, subjected to higher risk of predation. The troop fission was preceded by a long process of increasing tendency for sub-trooping. It was initiated by the four resident males who kept a large distance apart from each other, herded oestrous female associates away from others and were followed by other females. The females generally tended to stay close to associates, males and females. These parties were followed by the peripheral and immigrant males who had no female associates, and eventually two distinct daughter troops were formed.     

Socio-ecological study ofPresbytis aygula in West Java

Field studies of the Sunda Island leaf monkey,Presbytis aygula, were made in the montane forests of West Java at an altitude of 1,400–1,800 m between September 1976 and August 1981. The troop size ofP. aygula varied from 3 to 12 animals and the population density was about 35 animals/km² in Patenggang and 11–12 animals/km² in Kamojang. They were organized essentially in one male troops, though the troops in the Patenggang area usually consisted of only an adult pair and its offspring. Home range size was about 14 ha in Patenggang and about 35–40 ha in Kamojang. Some of those ranges overlapped with each other. The differences between these two areas were considered to be the result of recent habitat destruction and human impact in Patenggang. Animals spent more time in resting than other activities during a day.P. aygula in Java, consumed mainly leaves, eating less fruits and other parts of plants. Troop cohesion was tight, but social interactions between troop members were rather infrequent. The patterns of intertroop encounters and vocal sounds were described.     

Breeding behaviors in the black howler monkey (Alouatta pigra) of belize

Adulterous breeding between a female howling monkey (Alouatta pigra) of one troop with a male of an adjacent troop occurred despite territorial defense between the two troops. The specific behaviors are described as well as a synopsis of daily events which occurred between the female and two males from adjacent troops. A discussion of how this interaction and the behavior patterns relate to what is known about breeding in howler monkeys and related species follows.     

Comparative study of grooming relationships among wild Japanese macaques in Kinkazan A troop and Yakushima M troop

The influences of socionomic sex ratio (SSR; adult males/adult female) and troop size upon male-male, female-female, and male-female grooming relationships were examined and compared between two wild Japanese macaque troops (Kinkazan A and Yakushima M troops) in Japan. The Yakushima M troop was smaller and had a higher-SSR than the Kinkazan A troop. Between the troops, (1) the male-male grooming frequency and number of partners were greater in the Yakushima M troop than in the Kinkazan A troop; (2) the female-female grooming frequency and number of partners were not different; and (3) the male-female grooming frequency and number of partners were not different. Based on these features, the patterns of female-female and male-female grooming relationships appear to be independent of SSR and troop size variations. In contrast, male-male grooming relationships are influenced by both factors, especially SSR. Frequent grooming interactions among males may be useful for the continued coexistence of relatively many males especially in a higher-SSR troop.     

Reactions to fear as a proximate factor in the sociospatial organization of baboon progressions

The objective of this study was to test the hypothesis that fearfulness is a key proximate factor determining the nonrandom order repeatedly reported for baboon troops progressing from one location to another. According to this hypothesis, the most vulnerable troop members, the walking immatures, are expected in most circumstances to be cautious and to keep others between themselves and potential danger. The more confident adults, especially large powerful males, should tend toward the front and rear of progressing troops. The fear hypothesis predicts that in progressions toward a fear source, adult males should be near the front of the troop; on the other hand, when the troop is retreating from a frightening or tense situation, adult males should be found more toward the rear. Progressions of chacma baboons away from the location of a severe fright or in retreat from another troop were compared with other progressions. Adult males tended to be more rearward in these situations. The number of adults of either sex interposed between a fear source and the first walking immature was greater for retreating troops than for others. Some adult males continued to be near the front of the troop when retreating from tense situations.     

Population organization of wild pig-tailed macaques (Macaca nemestrina nemestrina) in West Sumatra

A field study on wild pig-tailed macaques was conducted in West Sumatra, Indonesia, during three periods from January 1985 to February 1987. During the nine months of the first two periods, unprovisioned monkeys were traced and observed. During the eight months of the last period, monkeys were provisioned and observed mainly at baiting sites. Three troops and ten solitary males appeared at the two baiting sites. Some males immigrated into and emigrated from the troops. The troops had a multi-male multi-female composition. The size of the various troops was 74, 49, and 81 individuals, respectively, and the mean adult sex ratio in the troops was 1:6.3; that is, markedly biased towards females. The home ranges of two of the troops overlapped considerably. When the troops encountered each other at the baiting sites, a clear dominance relationship was recognized. The troops differed in their integration as ranging units: two of the troops did not form subgroups (temporary fission and fusion of each troop), while the other troop frequently split into subgroups. Recent field studies on pig-tailed macaques have suggested a multi-leveled society with harem-type unit groups. However, in the present study, the troops observed had neither a substructure similar to harem-type groups nor a superstructure that emerged as a result of fusion of the troops. The unit group of the pig-tailed macaques appears to be a multi-male, matrilineal group.     

The variable social organization of hanuman langurs(Presbytis entellus), infanticide,and the monopolization of females

Data from 24 wild populations of hanuman langurs (Presbytis entellus)in south Asia are used to test hypotheses seeking to explain variation in troop structure and the incidence of infanticide. The occurrence of infanticide is associated with a one-male troop structure and not with a high density. The density, predation, and economic-advantage hypotheses, as explanations for the occurrence of one-male and multimale troops, are not supported by the review. However, the monopolization hypothesis is not contradicted; the number of adult males per troop is significantly correlated with troop size and with the number of adult females per troop. Therefore it is suggested that a one-male troop structure will arise if a male is able to monopolize a group of females, a multimale troop if he cannot. One-male troops may predispose to infanticide because of high variance in male mating success and high intermale competition between groups rather than within troops. If female dispersion determines troop structure, it is speculated that females could manipulate males to form a multimale society if the advantages in terms of infant survival and intertroop conflict exceeded the costs in terms of not producing infanticidal “sexy sons.”     

Patterns of movement by baboons in the Drakensberg mountains: Primary responses to the environment

The movement patterns of two chacma baboon troops in the Drakensberg mountains of South Africa were studied over an 18-month period. One of these troops (HIGH) lived on the escarpment slopes (1920–2980 m), while the other (LOW) lived primarily in the montane belt (1560–2000 m). In this paper we analyze the effects of environmental variables on day journeys and home range use. We found the troops to be similar in the temporal patterning of their daily movement, in the resistance of travel speed to variations in local climatic conditions, and in their response to the nutritional bottleneck at the end of the austral winter. While both troops traveled farther as food became scarcer, HIGH troop undertook longer day journeys than LOW troop. This was probably due to the interactive effects of absolutely lower food availability and lower ambient temperatures. HIGH troop traveled farther when food was scarcer and when minimum temperatures were higher. Neither variable accounted for variance in the day journeys of LOW troop. Both troops used some areas of their home ranges preferentially. For LOW troop this preference followed the spatial distribution of food. While the same was generally true for HIGH troop, its home range use was complicated by the adverse temperatures of winter and spring. It abandoned the higher, more productive part of its range once temperatures became severe, returning only after minimum ground temperatures had risen above 0°C. These usage patterns differ from those described for eastern African baboon populations and reflect both the severity and sesonality of climate and the poor quality and extreme dispersion of food that characterize these southern mountains.