Troop Histories and Range Inertia of Lemur catta at Berenty,Madagascar: A 33-year Perspective

Lemur catta troops in a 1-km ² study area at Berenty Reserve have maintained fidelity to core areas since Budnitz and Dainis' study of 1972–1973, and for two troops possibly since 1963. Population in 1 km ² fluctuated from 155 to 105 to 282 individuals (excluding infants), and the number of troops increased from 12 to 21. Most troops retain the same core areas from year to year (170 observed troop-years). Ten troops derived from known fissions have settled in parts of their parent troop range or an adjacent neighbor's range. Five more troops may derive from similar matrilocal fissioning, inferred from behavior and ranging patterns. One has remained unchanged. Five have unknown parentage, in the ranges of four previously censused troops. Once a fissioned troop completely replaced another, one troop permanently extended its range, three times females joined a different troop, once a female remained nomadic for two years without stable home range. No fissioned troop has been seen to leapfrog others: to settle discontiuously from its parent. Intertroop antagonism may reflect benefits of long-term core area control.     

Social Relationships Among Ring-Tailed Lemurs (Lemur catta) in Two Free-Ranging Troops at Berenty Reserve, Madagascar

We observed two free-ranging troops of ring-tailed lemurs at the Berenty Reserve, Madagascar. Kinship affinities in these troops are known only for mothers and their offspring 4 years of age. We attempted to quantify social relationships. Almost all agonistic interactions were dyadic, and triadic agonistic interactions, such as alliances, were very rare. Dominance hierarchies in both sexes in the two troops were not linear. As in cercopithecine monkeys, mothers were dominant over their adult daughters. However, the daughters were not ranked immediately below their mothers. Close proximity and social grooming occurred more frequently between closely related females, such as mother–daughter and sister–sister dyads, than between unrelated females. Frequent-proximity relations also occurred between adult males that had emigrated from another troop and entered the present troop together, even though they did not rank closely to one another. Subordinates were likely to groom and to greet dominants more frequently than vice versa. During group encounters, particular females were involved in agonistic interactions with animals of other troops, regardless of dominance rank. Adult males, regardless of their dominance rank, but not adult females, constantly tried to drive solitary males away.     

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.”     

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.     

Survey of the black howler monkey,<Emphasis Type="Italic">Alouatta pigra</Emphasis>, population at the Mayan site of Palenque,Chiapas, Mexico

A survey of the population of the black howler monkey (Alouatta pigra) present at the Mayan site of Palenque was conducted during 2000. A total of 911 man/hours, spread over 112 days were spent surveying the 600 ha area of pristine forest at the site for howler troops. We detected the presence of 136 individuals of which 131 were members of 20 troops, the rest were 3 solitary adult males and 2 adult males travelling as a pair. Ecological density was estimated at 23 individuals/km². Mean troop size was 7.0 individuals and it ranged from 2–12 individuals; 60% of the troops were multimale. All sighting of howler monkeys were in evergreen rain forest and 75% were in trees ≥20 m in height. The reported densities and mean troop size are higher than those reported for the species in Guatemala and in central Quintana Roo, Mexico. The vegetation of the forest contains tree species reported to be used by species ofAlouatta in the Moraceae, Sapotaceae, Leguminosae, and Lauraceae plant families. Protection of a large perimeter area (ca 1700 ha) around the archeological site by the Mexican government ensures the conservation of the forest and of the black howler monkey population present at the site.     

Life history variables of wild troops of formosan macaques (Macaca cyclopis) in Kenting,Taiwan

A study on population dynamics of wild Formosan macaques (Macaca cyclopis) in Kenting, southern Taiwan, was conducted from March 1985 to August 1990. At first, only one monkey troop was studied. It fissioned in 1987 and both of the daughter troops have been observed since then. Total number of animals increased from 10 to 29 over the years, but the sizes of individual troops have never been more than 20. Seasonality in breeding has been detected: copulations were concentrated in the period from November to January and 75% of all the 28 births occurred between April and June. Time of birth by parous females without offspring from the preceding year was earlier than that of lactating females. Young females gave their first births at 4 or 5 years of age. Total birth rate over the study period was 0.8 infant per female per year. Hunting was the main cause of death while natural mortality rate was low for the animals. There was only one adult male in each troop for most of the time. Troop males in the two daughter troops have been replaced two or three times in the three years by some solitary males that moved around in the area. The reproductive parameters of Formosan macaques in Kenting were found to be more similar to that of rhesus monkeys than to Japanese macaques. And a case of higher reproductive success in a high-ranking matriline was reported.     

Population and social dynamics changes in ring-tailed lemur troops at Berenty,Madagascar between 1989 - 1999

In the present study, we recorded all births, immigrations, deaths, and emigrations for a population of ring-tailed lemurs at Berenty Reserve, Madagascar, between September 1989 and August 1999. In September 1989, three troops (C, B, and T) inhabited the study area of 14.2 ha. During the 10-year period, eight troop divisions, six evictions of females, and three troop takeovers of ranges by other troops occurred in and around the study area. Consequently, in August 1999, the number of troops in the same area increased to six (CX, C1, C2A, C2B, T1, and T2). The number of lemurs aged >1 year increased from 63 to 82, which resulted from 204 births, 58 immigrations, 125 deaths, and 118 emigrations. Of the 204 newborn lemurs during the study period, 103 died, 44 emigrated outside the study area, and 57 remained within the study area. The total number of lemurs that emigrated from natal troops was 69 (54 males and 15 females). Natal males left their troops around the age of 3. Non-natal males changed troops after a tenure varying from 1 to 7 years. Survival curves showed a fall in survival rates of both sexes to < 0.5 between the ages of 2 and 3. For females, the survival rate gradually decreased to < 0.2 at the age of 9. On the other hand, due to emigration, the survival rate of males could not be determined after the age of 5 yr. Since some males attained high-rank at the age of 6 – 10 yr, the prime age for male ring-tailed lemurs is thought to be around 7 – 10 yr. Ring-tailed lemurs are essentially female philopatric, because all cases of females leaving natal troops resulted from troop divisions or forced evictions. Such social changes may have resulted from competition among females. All cases of troop divisions or evictions occurred in larger troops consisting of ≥20 lemurs, and only a few females could rejoin their troops. When males joined such a female-group, a new troop was formed. Although promoted by an increase in population, frequent emigrations of females from original troops are the characteristics of ring-tailed lemurs at Berenty.     

Ecology and behavior ofPresbytis thomasi in Northern Sumatra

A field study of 23 bisexual troops, ranging in size from 3 to 21 members ( =8), and two all-male groups of the Thomas's leaf monkey (Presbytis thomasi) was conducted in North Sumatra from November 1981 to April 1984. Most troops (N=19 or 82.6%) contained only one adult male. Two troops and one group were most intensively studied. The home range was 12.3–15.7 ha for the two bisexual troops, and only 1.7 ha for the one, all-male, ten-member group. Fruits composed more than 50% of their diets. Vocalizations were classified into 13 types. Births occurred at any time of the year. Among three males of a bisexual troop, serious fights were observed: two males died of wounds and the former beta male became the new alpha male. After this social change, the home range area of this troop gradually shifted eastward. But, 3.5 months after the social change, a 9-month-old infant male stayed alone in the western part of its former range. Thereafter, he became a solitary male and sometimes went into the riverine area of the Bohorok river. The occurrence of male replacement suggests instability of multi-male organization in bisexual troops. Moreover, the different mortality rate between males and females and the unequal sex ratios forced by the formation of one-male troops, maintained high tension levels among males competing on females.     

Status of Trachypithecus geei in a Rubber Plantation in Western Assam, India

Golden langurs (Trachypithecus geei) are an endangered species in a limited area of Northeast India and Bhutan. They are confined to a forest belt in western Assam between the Manas River in the east, Sankosh in the west and Brahmaputra in the south along the Indo-Bhutan border. Due to habitat destruction, their populations are restricted to fragmented forest pockets, especially in India. We compared data on an isolated population of golden langurs in the rubber plantation of Nayakgaon in the Kokrajhar district of Assam, May 2002 with an earlier census in 1997. We counted a total of 52 individuals in 3 troops in 2002. The average troop size is 17.3 (r = 7–26). The ratio of adult male to adult females is 1:3.16. Of the total population 9.6% were adult males, 21.1% were adult females, 17.3% subadult males, 7.7% subadult females, 19.2% juveniles and 25% infants. In 1997 Srivastava et. al., recorded 38 individuals in 5 troops with an average troop size of only 7.6 . Apparently troop fusion has occurred. The increased population is encouraging.     

Survey and census of howler monkeys (Alouatta palliata) in the rain forest of “Los Tuxtlas,” Veracruz,Mexico

Howler monkey troops were censused at the biological reserve “Los Tuxtlas” in Veracruz, Mexico. The reserve includes 700 ha of rain forest. Twenty howler monkeys were also trapped, measured, marked, and released. Censuses were conducted for a period of 26 months, and they indicated the existence of 17 troops. The mean troop size was 9.12 (SD ± 2.93), and mean troop composition was 3.0 adult males, 4.12 females, 1.56 juveniles, and 1.54 infants. Ecological density was 0.23 howlers/ha or 23.29 howlers/km². The male to female ratio was 1:1.37. No discrete seasonality in births was noted. Howler monkeys in this locality inhabit the northernmost limit of the neotropical rain forest. The population parameters fall within those reported for Alouatta palliata at other sites.     

Life-history characteristics of a wild population of vervets (Cercopithecus aethiops sabaeus) in Barbados,West Indies

Life history data are presented for a population of vervets, Cercopithecusaethiops sabaeus, in Barbados, West Indies. The data were obtained from two habituated troops and from vervets captured during a large-scale trapping program. Individuals of known age from one troop were weighed periodically, and separate growth curves generated for males and females. The mean weight of captured adult females was 3.3 kg; that of adult males, 5.3 kg. The average age at sexual maturity is estimated at 34 months for females and 60 months for males. Vervets give birth throughout the year, but most infants are born between April and July. The average interbirth interval following a surviving infant is 11.8 months. The mortality of juveniles is heaviest between birth and 2 years of age and decreases thereafter. Males emigrate from their natal troops at sexual maturity and one incident of a juvenile female emigrating is reported.     

Social stability and change among forest hanuman langurs (Presbytis entellus)

The social organization of hanuman langurs (Presbytis entellus, Colobinae) was studied in Kanha Tiger Reserve, Central Indian Highlands between 1980 and 1983, followed by six brief return visits over ten years. Censuses of the 7 km² Kanha meadows demonstrated little change in population density and structure between 1982 and 1990; the population was consistently composed of one-male troops and all-male bands. During the return visits the focal C troop extended its known 74.5 ha range by only 5.6%. By 1993 two identified, habituated, adult females remained within the troop. The adult male was resident in C troop for ≥nine years and eight months.     

Population structure,demography, and dynamics of mountain baboons: An interim report

Counts of 61 baboon troops (Papio cynocephalus ursinus) at four localities in the Drakensberg mountains confirmed earlier reports of a small mean troop size. This troop size of 22.49 animals changed neither with latitude nor elevation. Data from two of the sites suggested that population density increases from south to north, while a working assumption of 2.5 animals/ km² allowed us to set the population size at 7,540 animals, living in 335 troops. Both the adult sex ratio of 2.07 females/male and the immature/ adult female ratio of 1.17 were unaffected by troop size. Repeated counts from nine known troops revealed that the population is at equilibrium. © 1995 Wiley-Liss, Inc.     

Socio-sexual factors of troop fission in wild Japanese monkeys (Macaca fuscata yakui) on Yakushima Island,Japan

The troop fissions which occurred in a wild population of Japanese monkeys (Macaca fuscata yakui) were observed from 1977 to 1979 on Yakushima Island. The fissions were initiated in the breeding season by non-troop males who established a consort relation with estrous females. In order to analyze the socio-sexual factors which accelerated the fissions, the male emigrations and immigrations before and after two successive fissions, and the copulation frequencies, competition among males and preferences of mating partners in both sexes in the 1977–78 breeding season after the first fission were examined. The results indicated that three factors (a large number of non-troop males, a shortage of troop males and the females' choice of mating partners) effectively influenced on the establishment of consort relationships between non-troop males and estrous females. It is suggested that these factors may exert different effects on the troop disorganization in relation to troop size. In small-sized troops, a large number of non-troop males and a shortage of troop males may lead to stronger competition between them, and the females' choice affected by prolonged intimate relations with the dominant TMs may reduce their priority of access to estrous females. This situation possibly stimulates fission or male emigration in small-sized troops under the natural conditions on Yakushima Island. In contrast, in large-sized troops under isolated conditions, a surplus rather than a shortage of troop males may contribute to troop disorganization, as most former studies have suggested. A higher socionomic sex ratio may decrease the mating activities of subordinate troop males and increase the competition among them. This situation possibly accelerates the fission of large-sized troops through prolonged interactions between females and subordinate or peripheral troop males. A lower ratio and the females' choice, however, raise the mating chances of subordinate troop males and may not promote the fission of large-sized troops under isolated conditions. This study was financed in part by a Grant-in-Aid for Special Project Research on Biological Aspects of Optimal Strategy and Social Structure from the Japan Ministry of Education, Science and Culture, and by the Cooperative Research Fund of the Primate Research Institute, Kyoto University.     

Effects of contextual and social variables on contact call production in free-ranging ringtailed lemurs (Lemur catta)

Ringtailed lemurs (Lemur catta)often emit a characteristic vocalization when resting as a troop. This “meow call” is believed to serve an intragroup contact function. I investigated the effects of behavioral context and proximity on call production and acoustic features of the vocalization in a free-ranging troop in the Berenty Reserve, Madagascar. When group members were dispersed, the meow call was given frequently, and the acoustic features of the call probably increased the locatability of the emitter. I evaluated social relationships among the troop members from grooming interactions and spacing data. I also studied the call exchange network among the troop members, the results of which indicate that calls are exchanged between the two subgroups of females, which they connect.     

An ecological study of troop fissions of Japanese monkeys (Macaca fuscata yakui) on Yakushima Island,Japan

Wild, habituated, Japanese monkeys were observed from 1975 to 1979 on Yakushima Island, Southern Japan. The monkey troops had a continuous distribution in a warm temperate forest. Demographic data on local populations was collected. The population density was 33 animals/km². The growth rate of the studied troop was 3.0% per year. A significant correlation between home range areas (R) and troop size (P) was found (r=0.955,p<0.005), using anR-P equation,R=1.84P. One troop split into three troops through two successive fissions. Twenty-one intertroop encounters were observed. Five types of encounters were distinguished. The encounters were apparently territorial defence. Increases in birth rate and socionomic sex ratio after the fissions were prominent. The following four factors had a direct effect upon the dispersion of the troops after fission: (1) dominance relation between the fission troops; (2) social pressure of the neighbors; (3) troop's attachment to its home range; and (4) structure of the environment. The home range of Japanese monkeys is a territory, and territoriality is a population regulating mechanism which serves to reduce competition for food.     

Spawning habitat selection and suitability for Japanese dace, Tribolodon hakonensis

We have investigated the effects of three current velocities and three substrate sizes (gravel to cobble) on the spawning behavior of Japanese dace, Tribolodon hakonensis, in spawning-induction and habitat-selection experiments. In the spawning-induction experiment under laboratory conditions the number of females induced to spawn was significantly fewer at low current velocity (ca. 5 cm s^–1) than at medium (ca. 30 cm s^–1) or high (ca. 50 cm s^–1) current velocity. Females spawned independently of substrate size in the experimental tank, and did not bury their eggs in the substrate bed. In the habitat-selection experiment under field conditions, females selected the substrate microhabitat and spawned more frequently at a site with medium substrate size (very coarse gravel; major axis ca. 40 mm) than at sites with small (fine gravel; ca. 8 mm) or large (cobble; ca. 70 mm) substrate size. We conclude that Japanese dace select spawning sites at least partly on the basis of current velocity and substrate size, which affects the survival rate of eggs.     

Population ecology and life history of the diurnal skink Morethia boulengeri in arid Australia

Summary The life history and population ecology of the skink Morethia boulengeri were studied from September 1985 to May 1987 in populations in a riverine woodland habitat and at an abandoned homestead in Kinchega National Park. The population dynamics and life histories of the two populations were remarkably similar. Yearly mortality (including emigration) ranged from 0.84–0.89. The yearly emigration rate was 0.01–0.03. Size-and body-condition-dependent mortality could be demonstrated for the population in riverine woodland. Average spring time densities were similar in both study sites but varied between years and ranged from 421-1823 individuals/ha. M. boulengeri females laid on average 2.8 eggs per clutch and usually produced three clutches per year. Egg mass was significantly correlated with female snout-vent-length, but relative clutch mass and egg size were not. All surviving juveniles reproduced for the first time in their first year. Some activity occurred throughout the year. Preferred body temperatures decreased in the cooler months. The data fit demographic models of life history evolution.     

Daytime deliveries observed for the ring-tailed lemurs of the berenty reserve, Madagascar

In the Berenty Reserve, Southern Madagascar, of the 16 deliveries recorded for ring-tailed lemurs from 1995 and 1997, 10 cases occurred during daytime hours (07:00 – 16:59). Four mothers lost contact with their troop members during parturition, but were able to rejoin them after about one hour. No attack from the individuals of the neighboring groups or predators on the mothers or their newborn infants was observed, whereas, other females of the mother’s own troop attacked them after delivery in two cases. Such daytime delivery may have originated from the circadian rhythm of the species’ nocturnal ancestors, who might have given birth during the daytime. This pattern may now be a non-adaptive feature, in agreement with the “evolutionary disequilibrium hypothesis (EVDH).”     

Vertical distribution of wild Yakushima macaques (Macaca fuscata yakui) in the western area of Yakushima Island, Japan: Preliminary report

A census of wild Yakushima macaques (Macaca fuscata yakui) was carried out in a 23-km² area of the western coast of Yakushima Island, Japan. We analyzed the census data to investigate changes in monkey distribution associated with the vertical distribution of vegetation. In the lowland coastal zone of 0–300 m above sea level (a.s.l.), 4.8 troops and 62.4–99.8 monkeys are estimated to have existed per km². In the mountainside zones of 300–900 m a.s.l., the troop density decreased to 1.3–1.6 troops/km². Since there was no difference in size between the coastal and mountainside troops, population density should decrease with altitude to about 30–36 monkeys per km². On the other hand, 2.4 troops and about 36 monkeys were estimated to have inhabited per km² in the mountain summit zone of 900–1,323 m a.s.l. Nature Conservation College