Showing papers in "American Journal of Primatology in 1990"
TL;DR: This report describes the composition of the diet of lowland gorillas, Gorilla gorilla gorilla, at Lopé in central Gabon, which is the most frugivorous population studied so far.
Abstract: This report describes the composition of the diet of lowland gorillas, Gorilla gorilla gorilla, at Lope in central Gabon. This population inhabits mature evergreen tropical forest and is not habituated to human observers. Data were collected during 6 years of an ongoing long-term study, from feeding-trails and by direct observation, but mostly by fecal analysis. Gorillas ate 182 plant foods from 134 species and 36 families. The fruit diet was diverse: 95 species were consumed, most with succulent pulp, and some immature seeds were eaten. Fruit remains were recorded in 98% of dung. Vegetative parts of Aframomum and Marantaceae formed staple foods, as they were abundant, accessible, and available year-round. Soil and social insects were also ingested; remains of weaver ants were recorded in one third of feces. More foods have been recorded for gorillas at Lope than elsewhere and this is the most frugivorous population studied so far.
191 citations
TL;DR: Quantitative data on free‐ranging C. derbianus in Costa Rica demonstrate that it is highly arboreal, uses visually directed predation to capture arthropod prey, and makes extensive use of terminal branch foraging, where it feeds on small angiosperm products, thus suggesting that the hypotheses are not mutually exclusive but are interdependent.
Abstract: The didelphid Caluromys shows evolutionary convergence towards prosimians in having a relatively large brain, large eyes, small litters, slow development, and agile locomotion The selection pressures that favored the emergence of primate-like traits in Caluromys from a generalized didelphid ancestor may be analogous to the selection pressures favoring the initial divergence of primates from a primitive nonprimate ancestor, and thus Caluromys provides an independent test of the arboreal hypothesis (Smith: Annual Report of the Board of Regents of the Smithsonian Institution 1912:553-572, 1913), the visual predation hypothesis (Cartmill: The Functional and Evolutionary Biology of Primates, pp 97-122, 1972), and the angiosperm exploitation hypothesis (Sussman: American Journal of Primatology, in press) of primate origins Quantitative data on free-ranging C derbianus in Costa Rica demonstrate that it is highly arboreal, uses visually directed predation to capture arthropod prey, and makes extensive use of terminal branch foraging, where it feeds on small angiosperm products These observations are consistent with predictions from each model of primate origins, thus suggesting that the hypotheses are not mutually exclusive but are interdependent The initial divergence of primates probably involved exploitation of the rich angiosperm products and associated insects found in fine terminal branches; visually directed predation may have evolved as an efficient method of insect capture in the terminal branch milieu
187 citations
TL;DR: This review examines the diversity of avian mixed foraging flocks with the goal of relating the conclusions to primate polyspecific associations, and finds that a paucity of ecologically compatible combinations of species seems to limit primatepolyspecific associations geographically to regions in which the presence of monkey‐eating raptors provides a strong incentive for aggregation.
Abstract: This review examines the diversity of avian mixed foraging flocks with the goal of relating the conclusions to primate polyspecific associations. Mixed associations are considered as adaptations for achieving an optimal balance between predator protection and feeding efficiency. In open habitat, predator and prey are able to detect each other at a distance and feeding competition is low, especially in species that subsist on a homogeneously distributed food supply. These conditions favor large groups of variable composition. In closed habitats, predators attack at close range, so early warning alarm systems are at a premium. Feeding competition is often intense because food resources such as fruit, flushing leaves, and nectar are spatially concentrated. Since feeding competition is generally less between than within species, these conditions favor mixed associations composed of small numbers of several to many species, and the evolution of elaborate early warning systems to thwart predators. The primate polyspecific associations that have been studied to date share characteristics with the closed habitat model while exhibiting some important distinctions. Primate associations are made up of integral troops, not individuals, implying high incremental costs of joining. These costs, plus a paucity of ecologically compatible combinations of species, seem to limit primate polyspecific associations geographically to regions in which the presence of monkey-eating raptors provides a strong incentive for aggregation.
184 citations
TL;DR: A long‐term study was carried out on a black howler monkey population living in 150 ha of forest patches spread out in a 3,000 ha rural area in Northern Argentina.
Abstract: A long-term study was carried out on a black howler monkey (Alouatta caraya) population living in 150 ha of forest patches spread out in a 3,000 ha rural area in Northern Argentina. A total of 22 different groups were located between 1980 and 1984 and 11 of these were monitored regularly during 28 months. Ecological density varied between 12.14 and 12.93 groups per sq km of thall dense forest (0.80 to 1.15 ind./ha; biomass 306 to 365 kg/sq km). Solitaries and small associations of adult or subadult individuals of both sexes were also recorded but occupied habitats of inferior quality. Mean sizes of reproductive groups varied from 6.4 to 8.4 and the range was 3 to 15 individuals. Reproductive groups had 1 to 3 adult males, 1 to 3 adult females, and several immatures. Sex ratio was biased toward females among the adults but it varied in other age classes. Births occurred throughout the year showing a peak in the colder and drier season. Subadult or young adult males and females dispersed from suspected natal groups and became solitaries or joined associations. Males invaded groups and displaced or coexisted with resident males. Infanticides and disappearances of infants were associated with male changes. Comparative censuses on an island not far from the main study area showed higher density and biomass (2.8 ind./ha; 1,117 kg/sq km) and different group sizes and composition. Habitat features as well as the history of each study site may account for the observed demographic differences.
182 citations
TL;DR: In prosimians, inter‐specific differences in sexual dimorphism were not correlated with variance in male reproductive success, and it is suggested that speed and agility of males, rather than size and strength, might have been favored by intra‐sexual selection in most prosimian primates.
Abstract: The four major hypotheses advanced to explain the evolution of sexually dimorphic characters invoke sexual selection, natural selection, allometry, and phylogenetic inertia. In this paper, each of these hypotheses is examined for its usefulness in explaining the inter-specific variation in sexual size dimorphism among prosimian primates. Data on body weight and the degree of sexual dimorphism were obtained for 32 prosimian and 95 simian species. Although prosimians exhibited significantly less sexual dimorphism than simians, there was nevertheless significant variation in dimorphism among them. The degree of sexual dimorphism in prosimians did not show significant variance at any taxonomic level, but the majority of variance occurred within genera. Thus, sexual dimorphism in size among prosimians is probably not constrained by phylogeny at the generic level and above. There was no significant correlation between body size and the degree of sexual dimorphism in prosimians, suggesting the absence of an allometric effect. Similarly there was no relationship between body size and sexual dimorphism among simians in this size range. This result suggested that the expression of sexual dimorphism may nevertheless be influenced by absolute size. In prosimians, inter-specific differences in sexual dimorphism were not correlated with variance in male reproductive success. It is suggested that speed and agility of males, rather than size and strength, might have been favored by intra-sexual selection in most prosimians. It seems also plausible that the relative monomorphism of most prosimians, especially in the Lemuriformes, might be a result of increased female size favored by natural selection. Consideration of all natural and sexual selective pressures that affect size in both sexes separately is required to understand the adaptive function and evolution of primate size dimorphism.
152 citations
TL;DR: The vervets' increased vulnerability to leopard predation in 1987 did not appear to be related either directly or indirectly to continued habitat deterioration because 1) mortality rates after 1987 decreased to pre‐1987 levels and 2) the vervetts' behavior did not appears to change to make them more vulnerable than in previous years.
Abstract: A substantial increase in mortality, due mainly to predation, occurred during 1987 in a population of vervet monkeys (Cercopithecus aethiops) studied from 1977 to 1989 in Amboseli National Park, Kenya. It has been shown that vervets moving into new and unfamiliar habitats are more at risk from predation. However, this does not entirely explain the increase in predation in 1987 because predation decreased after 1987 while movement into new areas continued. An increase in leopard alarm calls relative to previous years in four of five groups, and an association between disappearances and leopard alarm calls given by vervets in the same four groups, suggest that leopards, a main predator of vervets, accounted for the increase in mortality. The vervets' increased vulnerability to leopard predation in 1987 did not appear to be related either directly or indirectly to continued habitat deterioration because 1) mortality rates after 1987 decreased to pre-1987 levels and 2) the vervets' behavior did not appear to change to make them more vulnerable than in previous years. The increased vulnerability appeared to be due in part to an increase in the presence of leopards. However, it is unclear why predator presence temporarily increased.
132 citations
TL;DR: Proboscis monkey social organization was studied at the Tanjung Puting National Park in Kalimantan Tengah, Indonesia and one‐male groups appear to be “female bonded”; adult females direct affiliative behaviors towards their offspring and other adult females, not towards the male.
Abstract: Proboscis monkey (Nasalis larvatus) social organization was studied at the Tanjung Puting National Park in Kalimantan Tengah, Indonesia, for 12 months. Data were collected on one-male groups and all-male groups by using scan sampling and event sampling while following groups. Evening census surveys were also conducted. Proboscis monkeys were found to follow the typical Asian colobine pattern of one-male social groups, with extra-group males forming all-male groups. These groups appear stable, with few changes in membership. One-male groups appear to be "female bonded"; adult females direct affiliative behaviors towards their offspring and other adult females, not towards the male. Nearest-neighbor data indicate some peripheralization of juvenile animals.
127 citations
TL;DR: One possible interpretation for these results correlates the degree of bipedal behavior of a species in its natural environment with its readiness to exhibit a unilateral population‐level hand preference with a bimodal distribution on all tasks.
Abstract: Hand preference was assessed in 12 gorillas (Gorilla gorilla gorilla), 13 orang-utans (Pongo pygmaeus abelii), and 9 gibbons (Hylobates lar) by using a floor retrieval task and a mesh retrieval task. Hand preference was also assessed in 8 gorillas and 8 orang-utans by using a task involving the unfastening of a hasp. A bipedal requirement during testing (mesh retrieval task) facilitated detection of hand preferences. A significant left-hand preference was found for the gibbons with 6 of 6 gibbons preferring their left hand on the mesh retrieval task. Similarly, a significant right-hand preference was found for the gorillas with 10 of 12 gorillas preferring their right hand on the mesh retrieval task. The data for the orang-utan suggest a bimodal distribution on all tasks. Since the gibbon and gorilla in the wild engage in bipedal locomotion more frequently than the orangutan, one possible interpretation for these results correlates the degree of bipedal behavior of a species in its natural environment with its readiness to exhibit a unilateral population-level hand preference.
113 citations
TL;DR: To investigate habitat‐related size variation, skull lengths of wild‐caught adults were used to compare sizes of closely‐related conspecific and congeneric “sister taxa” to reveal a consistent pattern of size variation.
Abstract: The living Malagasy prosimians and their recently extinct subfossil relatives include about 20 genera and 8 families that can be considered one contemporenous fauna. They exhibit morphological, behavioral, and ecological differences comparable to living anthropoid primates. This diversity is matched by the equally varied topography, climate, and vegetation of Madagascar. To investigate habitat-related size variation, skull lengths of wild-caught adults were used to compare sizes of closely-related conspecific and congeneric "sister taxa." More than 1,550 museum specimens were examined representing virtually all known forms of extant and subfossil Malagasy prosimians. A total of 98 pairwise, sister-taxa comparisons among 76 different taxa from six broadly defined ecogeographic regions revealed a consistent pattern of size variation: (1) the smallest Malagasy prosimians inhabit the semiarid forests, bush, and thickets of the South; (2) next largest are those from the dry deciduous forests of the West and the humid but seasonal forests of the Sambirano; (3) larger yet are those from humid tropical and secondary forests of the East; and (4) the largest of all are the extinct forms of the central highlands that lived in what was probably a savanna-bush-woodland mosaic in the past but is now grasslands devoid of living prosimians. Taxa from the extreme North are more variable in size (small, intermediate, or large), which may reflect the mixture of local habitats in northern Madagascar. The ecogeographic size differences may be adaptive responses related to the carrying capacity of local environments such that smaller-sized species are favoured where the resources they exploit are more limited. Field observations on behavioral thermoregulation, home range size, and population densities offer some support for this hypothesis. Ecologically induced size differences among local populations were probably one factor in speciation events leading to the modern diversity of the Malagasy primates.
111 citations
TL;DR: The results suggest that the particular ecological setting greatly influences the nature of the interaction between species, through its effect on population structure, dietary overlap, food distribution, and community composition.
Abstract: Sympatric guenons in East Africa associate with one another in mixed-species groups to an intermediate degree. This makes it possible to compare a given group's ecology and behavior when it is part of an association to when it is unaccompanied, and to correlate association tendency with various ecological parameters. Two studies incorporating these approaches have been made of sympatric Cercopithecus ascanius and C. mitis monkeys in the Kakamega Forest, Kenya, and the Kibale Forest, Uganda. The pattern of and reasons for association in each site are reviewed. Compared to Kakamega, association between C. ascanius and C. mitis in Kibale occurs less often, and the species appear to benefit relative to one another in different ways. These results suggest that the particular ecological setting greatly influences the nature of the interaction between species, through its effect on population structure, dietary overlap, food distribution, and community composition. The major ecological differences between the two study areas probably reflect post-Pleistocene history and possibly climate, but they have important consequences for the present-day population structure and feeding ecology of each species, and hence affect relations between them as well.
107 citations
TL;DR: The data presented here, based on a 9 month study of a semifree‐ranging colony, supports the idea that females do indeed mate indiscriminately and at a high rate.
Abstract: The mating behavior of female Barbary macaques (Macaca sylvanus) has been called "promiscuous" because females mate with multiple males in rapid succession. The data presented here, based on a 9 month study of a semifree-ranging colony, supports the idea that females do indeed mate indiscriminately and at a high rate. Five hundred six copulations were recorded for 21 females during the breeding season, and 358 of these copulations occurred when females were in extended estrous cycles. As the days that females spent in estrus increased, either because they had longer cycles or more cycles than some other females, the number of different male partners also increased. There was no association between mating behavior and either male-female friendships or male care of infants born the following birth season. Promiscuity cannot be explained by selection to confuse paternity. There is also no evidence that females exchange copulations for support or affiliation. Female Barbary macaques mate with multiple males because males are unable, or are unwilling, to stop them.
TL;DR: Estradiol was the predominant urinary estrogen, however both estrone and estradiol were excreted in extremely high concentrations and LH peaks were discrete with urinary estrogens increasing at the time of the LH peak and remaining elevated throughout the luteal phase of the cycle.
Abstract: By retrospective review of colony records and determinations of urinary hormones we have described the reproductive profile of the female pygmy marmoset (Cebuella pygmaea). The pygmy marmoset is a nonseasonal breeder and gives birth to twins 76% of the time with single births occurring 16% and triplet births 8% of the time. Interbirth intervals ranged from 149-746 days. First births occurred to females between 24-42 months of age and 5-27 months post pairing. We measured urinary estrone, estradiol and estrone conjugates along with immunoreactive luteinizing hormone/chorionic gonadotropin (LH/CG). The postpartum LH peak occurred a mean of 15.6 days following parturition. The conception rate was 69% following the postpartum ovulation. Levels of CG rose a mean of 19 days following the LH peak in conceptive cycles and remained elevated for a mean of 76 days. Gestational length was a mean of 141.9 days from the LH peak to parturition. Only one female of the five studied displayed ovarian cycles which were a mean of 27 days in length. Estradiol was the predominant urinary estrogen, however both estrone and estradiol were excreted in extremely high concentrations. LH peaks were discrete with urinary estrogens increasing at the time of the LH peak and remaining elevated throughout the luteal phase of the cycle.
TL;DR: Both tamarin species appeared to occupy a similar ecological niche, but differences were highlighted in their methods of insect foraging, their preferred height in the forest, and their mode of travel.
Abstract: A 5 month field study was conducted in the Pando Department of northern Bolivia, on two tamarin species: the red-bellied tamarin, Saguinus l. labiatus, and the saddle-back tamarin, S. fuscicollis weddelli. Data were collected both by observation and radio-location on the group sizes, ranging behavior, daily activity patterns, and intergroup interactions. The two tamarin species formed stable mixed associations and each mixed species troop shared a common home range which they jointly defended against neighboring mixed species troops. Both species appeared to occupy a similar ecological niche, but differences were highlighted in their methods of insect foraging, their preferred height in the forest, and their mode of travel.
TL;DR: Observations are not compatible with the idea that ruffed lemurs live in small pair‐bonded groups, as other researchers have suggested, but alloparental care may increase the likelihood of infant survival.
Abstract: Parental behavior and infant development of black and white ruffed lemurs (Varecia variegata) were studied on Nosy Mangabe Island in northeast Madagascar. Ruffed lemur females produced twins, prepared nests for neonates in the trees, transported infants by mouth, and parked them in the trees. During two consecutive birth seasons, the average birth rate for nine females was 0.58. Two females reproduced in one social group. Lactating females spent most of their time resting with their infants or foraging for food. Infants developed rapidly and were fully mobile by 3-4 months. No female reproduced successfully in 2 consecutive years. In 1988, infant mortality within 3 months of birth was very high (64%). Accidental falls may have been one major cause. Adults of both sexes, including a reproductive female, exhibited alloparental behavior such as guarding infants and nonmaternal nursing. Alloparental care may increase the likelihood of infant survival. Some of these observations are not compatible with the idea that ruffed lemurs live in small pair-bonded groups, as other researchers have suggested.
TL;DR: It is suggested that olive colobus has a strong tendency to associate with other monkeys as part of an evolved strategy; that observed association patterns depend on the ranging habits and group dispersion patterns of the other species in the area; and that this strategy reduces predation risk for a small‐bodied monkey that forages in small, dispersed groups.
Abstract: Close association between olive colobus (Procolous verus) and other monkeys (especially Cercopithecus species) has been observed throughout the range of P. verus in the forest zone of West Africa. To investigate the basis of this association, we made new observations in Sierra Leone, concentrated at Tiwai Island. We obtained data on the association patterns of monkeys over a large area of the island from line-transect samples, and studied association behavior via long-term observational sampling of habituated groups of olive colobus and Diana monkeys (C. diana). During transect sampling, olive colobus always were seen less than 50 m from monkeys of other species, especially Cercopithecus. In studies of habituated groups, we found that one groups of olive colobus associated closely with a larger groups of Diana monkeys for more than 3 years. Members of the two groups were within 50 m of each other on over 80% of scan samples; the two groups shared the same range, but foraged in different parts of the canopy and had little dietary overlap; association was maintained by the behavior of the colobus. The olive colobus was the only Tiwai monkey species seen less than 50 m from members of a secon Diana study group more frequently than expected, although in this case the two species were associated during less than 12% of samples. In both cases, we detected month-to-month variation in association frequency. We suggest that olive colobus has a strong tendency to associate with other monkeys as part of an evolved strategy; that observed association patterns depend on the ranging habits and group dispersion patterns of the other species in the area; and that this strategy evolved because it reduces predation risk for a small-bodied monkey that forages in small, dispersed groups.
TL;DR: Analysis of the genetic distances among five baboon subspecies based on blood marker information from nine polymorphic protein loci available for baboons resident at the Southwest Foundation for Biomedical Research showed that significant genetic differences exist among the subspecies.
Abstract: The use of common names which may encompass a number of subspecies or species is pervasive in the biomedical literature. Failure to identify the complete taxonomic classification of research subjects presents a source of error for scientists attempting to evaluate results or to repeat experiments. This paper examines the problem in a common animal model, the baboon. Analyses of the genetic distances among five baboon subspecies (Papio hamadryas anubis, P.h. cynocephalus, P.h. papio, P.h. ursinus, and P.h. hamadryas) based on blood marker information from nine polymorphic protein loci (ADA, APRT, C3, CA1, CA2, GPI, MPI, PEPB, and PGD) available for baboons resident at the Southwest Foundation for Biomedical Research are presented. Statistical tests on the distances showed that significant genetic differences exist among the subspecies. A comparison of P.h. anubis and P.h. cynocephalus revealed that these two subspecies also differ significantly for biomedically relevant lipoprotein cholesterol levels, as can be predicted from the genetic distances. The results emphasize the pitfalls of using different types of baboons interchangeably in experimental protocols.
TL;DR: Analysis of long‐range vocalizations given by spider monkeys revealed consistent acoustic differences among the calls of individuals, which could benefit spider monkeys, where individuals forage separately in subgroups and the interactions between specific pairs of individuals is highly variable.
Abstract: Analysis of long-range vocalizations given by spider monkeys revealed consistent acoustic differences among the calls of individuals. Of seven acoustic measurements, four exhibited significant variation between individuals. A discriminant analysis demonstrated that two of these variables allowed correct identification of the caller 44% of the time. Including the remainder of the variables increased the percentage correctly identified to 50%. Individual identification by call structure could benefit spider monkeys, where individuals forage separately in subgroups and the interactions between specific pairs of individuals is highly variable. Acoustic recognition of callers would facilitate the choice of which subgroups to join, thus allowing individuals to manipulate the size and composition of their subgroups. In addition, the calls of mothers and offspring appeared to be similar in acoustic properties.
TL;DR: It is concluded that interspecific interactions and mutual calling incur some costs to the associated species but that these costs may be low.
Abstract: This study examined the social interactions between moustached tamarins, Saguinus mystax, and saddle-back tamarins, Saguinus fuscicollis, living in a mixed-species troop at the Rio Blanco, Peruvian Amazonia, between July 1985 and July 1986. Mixed-species troops were common among the S. mystax and S. fuscicollis populations in the Rio Blanco study area; 72% of all sightings of S. mystax and 82% of all sightings of S. fuscicollis were in mixed-speices troops (study group excluded from analysis). In the study group, the two species spent on average 82% of time in association. Interactions were observed at a rate of one per 5 h of observation. Most interactions (96%) were agonistic. About 70% of agonistic interactions occurred at small food resources (crown diameter < 5 m and/or limited number of ripe fruits). Moustached tamarins were always dominant over saddle-back tamarins. Friendly interactions were extremely rare and were restricted to play invitations. Mutual calling was observed in the morning before the two species joined each other and during the day when they became separated. It is concluded that interspecific interactions and mutual calling incur some costs to the associated species but that these costs may be low.
TL;DR: It is suggested that fathers are more responsive to infants than are mothers, and mothers may limit their involvement in infant care, as has been proposed by field results, due to an energetically demanding reproductive strategy.
Abstract: Infant care behavior was examined for 35 litters of 23 different groups of captive cotton-top tamarins. The behavior of mothers and fathers was compared to determine the effects of infant number and helper presence on each parent and to determine whether parents differed in responsiveness to infants. For young infants (1-4 weeks), the contribution of fathers to infant carrying was negatively correlated with helpers' contribution; as helpers carried more, fathers carried less. In contrast, the mothers' contribution to infant carrying was unaffected by helper contribution. Mothers carried older infants (5-8 weeks) less than did fathers, regardless of infant number or helper contribution. Fathers and mothers were equally likely to retrieve a non-harassed infant; however, fathers were more likely than mothers to retrieve an infant being harassed. These results suggest that fathers are more responsive to infants than are mothers. Mothers may limit their involvement in infant care, as has been proposed by field results, due to an energetically demanding reproductive strategy.
TL;DR: It is demonstrated that EIA measurements of ovarian hormones in daily urine samples can be used to accurately monitor ovarian function and early pregnancy in Macaca mulatta.
Abstract: Paired urine and serum samples from four conceptive and six nonconceptive ovarian cycles of seven adult Macaca mullatta were analyzed by radioimmunoassay (RIA) for circulating estradiol (E2) and progesterone (Po), and urinary estrone conjugates (E1C) and immunoreactive preganediol-3-glucuronide (iPDG) using enzyme immunoassay (EIA). Nonconceptive cycles exhibited a fivefold increase in urinary E1C and serum E2 levels from follicular phase levels to the preovulatory peak. Linear correlation between urinary E1C and serum E2 nonconceptive cycle hormone levels was significant (P <0.01, r = 0.69). Luteal phase levels of iPDG and serum Po levels were approximately parallel in nonconceptive cycles. Similarly, conceptive cycle urinary E1C levels and serum E2 measurements had a correlation coefficient that was significant (P<0.01, r = 0.45). Nonconceptive and conceptive cycle iPDG and Po levels were significantly correlated (P = 0.05, r = 0.63, and P<0.01, r = 0.66, respectively). These data demonstrate that EIA measurements of ovarian hormones in daily urine samples can be used to accurately monitor ovarian function and early pregnancy in Macaca mulatta.
TL;DR: Preliminary observations on anterior tooth use in these species at Hato Masaguaral, in the Llanos of Venezuela, provide suggestions regarding how foraging patterns reported in the literature relate to these microwear differences.
Abstract: Dental microwear features on the labial surfaces of maxillary central incisors of wild-shot museum specimens of Cebus olivaceus (n = 11) and Alouatta seniculus (n = 7) were examined at 200 × by polarized light microscopy. While wear scratch orientation patterns do not differ between the two samples, Cebus has a significantly higher density of wear features, and displays scratches that extend further cervically. Preliminary observations (n = 50 hours) on anterior tooth use in these species at Hato Masaguaral, in the Llanos of Venezuela, provide suggestions regarding how foraging patterns reported in the literature relate to these microwear differences. Cebus uses its front teeth more frequently in the manipulation of a greater variety of objects than does Alouatta.
TL;DR: Results of this short‐term study suggest that effects of association on resource use differ for the two species, and are related to the size of resources as well as to differences in body size and group size between the species.
Abstract: Short-term associations between primate species offer the opportunity to measure changes in individual behavior and ecology in response to alterations in group size and composition. During a three-month study of associations between squirrel monkeys (Saimiri sciureus) and brown capuchin monkeys (Cebus apella) in Manu National Park, Peru, I measured resource use and feeding efficiency for both species when in mixed and solitary troops, as well as the context and outcome of competitive interactions. Saimiri traveled among Cebus home ranges and were periodically led by Cebus to large fruiting and flowering trees. Feeding rates in large fruit trees were altered by the presence of the other species-positively for Cebus, but negatively for Saimiri. Association increased the average diameter of the troop only for Cebus, which could control access to small, concentrated resoures found while the mixed troop moved through the forest. Results of this short-term study suggest that effects of association on resource use differ for the two species, and are related to the size of resources as well as to differences in body size and group size between the species.
TL;DR: This study identified several variables that appeared to promote mixed‐species troop cohesion and yet maintained spatial segregation between species, which may help explain how two congeneric species accommodate one another with little apparent interspecific aggression.
Abstract: Mixed-species troops composed of two species of tamarin monkeys, and rarely other ceboids, occur throughout much of western Amazonia and are notable for their long-term stability. This study identified several variables that appeared to promote mixed-species troop cohesion and yet maintained spatial segregation between species. Three variables enhanced in terspecific spatial segregation: differences in support use, vertical stratification, and interindividual spacing. In contrast, early morning vocalizations and well-coordinated movement patterns contribute to cohesion within a mixed-species troop. The combination of these variables may help explain how two congeneric species accommodate one another with little apparent interspecific aggression. The exact nature of benefits and costs to each individual in a mixed troop is still elusive; however, a comparison of population densities of sympatric and allopatric tamarins suggests that population growth of one partner (Saguinus fuscicollis) is enhanced in the presence of a congeneric species.
TL;DR: The results suggest that the concept of maternal style can be used to describe variation between both individual Cayo Santiago mother–infant pairs and between individual Caye Santiago mothers.
Abstract: This paper assesses the extent to which free-ranging rhesus monkeys (Macaca mulatta) on Cayo Santiago show consistent mother-infant interaction with individual infants over time and consistent maternal styles from one infant to another. Inter-pair differences in several measures of mother-infant interaction related to proximity and contact were correlated positively and highly significantly between 6-week age periods. Analysis of variance methods were used to show that, after the first 6 weeks, these measures of interaction were also more similar among pairs with the same mother (i.e., families) than among pairs with different mothers. Differences between families were also consistent between age periods, and appeared to be due primarily to differences between mothers rather than to differences between sets of infant siblings. The results suggest that the concept of maternal style can be used to describe variation between both individual Cayo Santiago mother-infant pairs and between individual Cayo Santiago mothers.
TL;DR: To test the prediction that the breeding success of captive cotton‐top tamarins could be improved by maintaining them in groups whose size and age‐sex composition resembled those of wild groups, data were collated from 6.5 years of records from a breeding colony that otherwise had housing and husbandry procedures similar to those of other successful colonies.
Abstract: To test the prediction that the breeding success of captive cotton-top tamarins (Saguinus (o.) oedipus) could be improved by maintaining them in groups whose size and age-sex composition resembled those of wild groups, data were collated from 6.5 years of records from a breeding colony that otherwise had housing and husbandry procedures similar to those of other successful colonies. Group size and composition in the colony closely resembled those of wild groups, and infant survival was the highest yet reported for the species, with 69% of the 124 infants born reared by their parents to adulthood, and a mean surviving litter size of 1.5 infants. Abortion, stillbirth, and parental neglect of infants were rare. Parity had several effects on reproduction: mean litter size decreased, but percentage infant survival increased; interbirth intervals decreased in length; and seasonality in reproduction was more pronounced for the first four litters born to breeding females than for their subsequent litters, with a birth peak in the spring. Although a spacious and complex physical environment, retention of offspring in their natal families until experience of several sets of infant siblings had been obtained, and non-invasive husbandry and research techniques may all have contributed to the colony's success, it seems possible that the improvement over other colonies is due to the resemblance of group composition to those of wild tamarins.
TL;DR: It is concluded that modest increases in cage size are less likely to enrich the environment of singly caged laboratory primates than are changes in social opportunities or increases in environmental complexity.
Abstract: Newly proposed federal regulations will mandate that singly caged non-human primates be kept in cages larger than the current minimum standard, or be given 4 hours in an exercise cage per week. In order to evaluate the effectiveness of increasing cage size in improving well-being, the behavioral and heart rate responses of 10 female rhesus monkeys (Macaca mulatta) to three different cage sizes were measured. With the exception of vocalizations, no significant differences in behavior were obtained. Grunts increased in the largest cage, following the birth of an infant in a cage within view of the test cages. No differences with respect to cage size were found in heart rate or activity level, although there were significant variations at different times of day. We conclude that modest increases in cage size are less likely to enrich the environment of singly caged laboratory primates than are changes in social opportunities or increases in environmental complexity.
TL;DR: Breeding Aotus nancymai on a large scale in captivity is feasible and a birth peak was observed from October to January, and the mean age of a group of 12 males born in the colony when their female mates produced offspring was 42.17 ± 10.73 months.
Abstract: There are few reports and poorly documented field studies about the reproductive biology of the owl monkey (Aotus spp.). Reproductive data were collected from a breeding colony of owl monkeys (Aotus nancymai) held at the Center for Reproduction and Conservation of Non-Human Primates in Iquitos, Peru, for the past 10 years. Seventy nine breeding pairs have produced 180 offspring in a period of 3,619 months, representing an average of about one offspring for every 20 months that a pair was housed together. Neonatal mortality in the first week was 7.1%. Litter size was almost one (99.4%). The mean age at first birth in a group of nine females born in captivity was 40.56 ± 7.82 (S.D.) months. The mean age of a group of 12 males born in the colony when their female mates produced offspring was 42.17 ± 10.73 (S.D.) months. Gestation length did not exceed 141 days. Interbirth interval averaged 12.72 months. A birth peak was observed from October to January. Breeding Aotus nancymai on a large scale in captivity is feasible.
TL;DR: The level and pattern of facial morphological variation among the subspecific populations of Saguinus fuscicollis is examined to evaluate their taxonomic status.
Abstract: Hershkovitz (Living New World, Volume 1. Chicago, University Press of Chicago, 1977, pp. 618-627, 634-666) identified 13 subspecies of Saguinus fuscicollis based on coat color variation on the head, neck, and shoulders. Other morphological differences among the subspecies are unknown. It has been suggested, however, that several of the taxa may be distinct at the specific level. In this report, we examine the level and pattern of facial morphological variation among the subspecific populations to evaluate their taxonomic status. Eleven facial measurements were recorded from the left side of 104 saddle-back tamarin crania. Significant morphological variation among the subspecies in facial heights and depths was detected with discriminant function analysis. Analyses of morphological differences between subspecies and among individual specimens relative to geographical and evolutionary distances (based on the metachromatic theory) were performed by using quadratic assignment procedures. These analyses indicate an absence of geographically related morphological variation across the species range while phylogenetic relationships are reflected in morphological similarities among groups and individuals. This finding is consistent with the formation of subspecific populations by relatively small founding populations budding off from a larger parent population, invading a new interfluvial basin, and then remaining relatively isolated, as suggested by Hershkovitz (Living New World Monkeys, Volume 1. University of Chicago Press, Chicago, 1977).
TL;DR: Four types of calls from Golden Lion Tamarins (Leontopithecus rosalia) were analyzed for sex differences in structure and found that long calls, chirps, chucks, and trills from males and females were quite discriminable, but trills were not.
Abstract: Four types of calls (long calls, chirps, chucks, and trills) from Golden Lion Tamarins (Leontopithecus rosalia) were analyzed for sex differences in structure. Six or more acoustic variables were analyzed for each call type. One or more variables from each call category differed significantly between the sexes. In addition, discriminant function analyses were conducted on male vs. female data for each call type. Long calls, chirps, and chucks from males and females were quite discriminable, but trills were not. That these differences exist is surprising given that callitrichid primates are otherwise quite monomorphic in structure and behavior. Possible functions served by sex differences in call structure include group censusing or assessing the sex of transient individuals.
TL;DR: Food patch choice was investigated in the A‐troop of wild Japanese monkeys of Kinkazan Island, Japan; some troop members (in many cases, low‐ranking ones) avoided feeding in a high‐quality but crowded patch, while more monkeys fed in the high‐ quality patch as the difference in patch quality became larger.
Abstract: Food patch choice was investigated in the A-troop of wild Japanese monkeys (macaca fuscata) of Kinkazan Island, Japan. The monkeys visited a Zelkova serrata tree 16 times and fed on its seeds for 43.5 min on average during the 36 day study period. The proportion of fallen seeds to total fallen seeds, the feeding speed, and the number of monkeys feeding on seeds in the crown and on the ground were recorded to clarify the decision factors involved in food-patch choice: when the monkeys visit the tree, do they feed on seeds in the crown or on the ground? The monkeys appeared to the patch quality by feeding speed; they chose a high-quality patch and fed there. As a result, they seemed to maximize seed intake. However, some troop members (in many cases, low-ranking ones) avoided feeding in a high-quality but crowded patch. When the quality of the two patches was equal, the monkeys separated into two groups (in the crown and on the ground) in a ratio of 1:1 to feed. As the difference in patch quality became larger, more monkeys fed in the high-quality patch. The frequency of agonistic interactions per individual increased on the ground as the number of monkeys feeding there increased. When the cost of agonistic interactions is considered, the net benefit (energy intake minus energy consumption from agonistic interactions) per individual in a higher-quality but crowded patch may be equal to that in a lower-quality but uncrowded patch.