Seed Dispersal by Golden-headed Lion Tamarins Leontopithecus chrysomelas in Southern Bahian Atlantic Forest, Brazil

Seed dispersal by small primates may be particularly relevant in areas where populations of larger frugivores have been reduced or extinguished by hunting and/or habitat disturbance. In this context, the aim of this study was to evaluate the role of the golden-headed lion tamarin Leontopithecus chrysomelas as a seed disperser in Atlantic forest remnants in Brazil. To this end, we opportunistically collected feces deposited during observations on the feeding behavior of two groups of golden-headed lion tamarins ranging in the degraded areas of the Una Biological Reserve, Bahia, Brazil, from February 2006 to January 2007. We collected 587 fecal samples, of which 524 contained seeds from 24 plant species, distributed over 13 families. Disregarding seeds of<3 mm, the majority of seeds recovered were bromeliad seeds. In general, ingestion of seeds by golden-headed lion tamarins did not improve the germination proportion or decrease the germination delay of seeds, with the exception of Aechmea spp. seeds. The tamarins encountered different habitats during their daily activity period, while feeding and defecating. Consequently, some seeds were transported to different habitats including disturbed areas. Thus, the role of seed dispersal in combination with the daily movement pattern of L. chrysomelas contributes to the persistence of fruit plants and epiphyte species and to the natural regeneration process within Atlantic forest remnants.     

High‐throughput sequencing of fecal DNA to identify insects consumed by wild Weddell's saddleback tamarins (Saguinus weddelli,Cebidae, Primates) in Bolivia

The genus Saguinus represents a successful radiation of over 20 species of small‐bodied New World monkeys. Studies of the tamarin diet indicate that insects and small vertebrates account for ～16–45% of total feeding and foraging time, and represent an important source of lipids, protein, and metabolizable energy. Although tamarins are reported to commonly consume large‐bodied insects such as grasshoppers and walking sticks (Orthoptera), little is known concerning the degree to which smaller or less easily identifiable arthropod prey comprises an important component of their diet. To better understand tamarin arthropod feeding behavior, fecal samples from 20 wild Bolivian saddleback tamarins (members of five groups) were collected over a 3 week period in June 2012, and analyzed for the presence of arthropod DNA. DNA was extracted using a Qiagen stool extraction kit, and universal insect primers were created and used to amplify a ～280 bp section of the COI mitochondrial gene. Amplicons were sequenced on the Roche 454 sequencing platform using high‐throughput sequencing techniques. An analysis of these samples indicated the presence of 43 taxa of arthropods including 10 orders, 15 families, and 12 identified genera. Many of these taxa had not been previously identified in the tamarin diet. These results highlight molecular analysis of fecal DNA as an important research tool for identifying anthropod feeding patterns in primates, and reveal broad diversity in the taxa, foraging microhabitats, and size of arthropods consumed by tamarin monkeys. Am J Phys Anthropol 156:474–481, 2015. © 2014 Wiley Periodicals, Inc.     

Vigilance in a Cooperatively Breeding Primate

Collective vigilance is considered a major advantage of group living in animals. We investigated vigilance behavior in wild mustached tamarins (Saguinus mystax), small, arboreal, cooperatively breeding New World primates that form stable mixed-species groups with saddleback tamarins (Saguinus fuscicollis). We aimed 1) to investigate whether vigilance patterns change according to individual activity and 2) to examine whether there is a social component of vigilance in their cooperative and nonaggressive society. We studied 11 factors that may influence vigilance and used this data to interpret the possible functions of vigilance. We observed 44 individuals in 3 mixed-species and 2 single-species groups of 2 populations that differed in population density and home range sizes. Vigilance changed greatly when individuals were engaged in different activities and individual vigilance was affected by different sets of factors depending on the activity. As vigilance decreased in proximity of conspecifics and heterospecifics when feeding, and in larger mixed-species groups when resting, we conclude that the predominant function of vigilance in mustached tamarins is predator related. However, the absence of the group size effect in very large single-species groups suggests that it may also function to maintain group cohesion. In the population with higher density and smaller home ranges individuals also increased their vigilance in home range overlap areas. We found no evidence that mustached tamarins monitor group mates to avoid food stealing or aggression. The effect of heterospecifics on individual vigilance suggests that collective vigilance might have been an important incentive in the evolution of tamarin mixed-species groups.     

Seasonal patterns of diet and ranging in two species of tamarin monkeys: Stability versus variability

From June through December, data were collected on the diet and ranging patterns of moustached (Saguinus mystax) and saddle-back (Saguinus fuscicollis) tamarin monkeys in the Amazon Basin of northeastern Peru. During this 7-month period, insects and nonleguminous fruits accounted for 83% of tamarin feeding and foraging time. Despite marked seasonal variation in rainfall and forest productivity, patterns of habitat utilization, day range, dietary diversity, resource exploitation, and activity budget remained relatively stable throughout the year. Moustached and saddle-back tamarins appear to solve problems of food acquisition and exploit patchily distributed feeding sites using a relatively limited set of foraging patterns. In general, these primates concentrate their daily feeding efforts on several trees from a small number of target plant species. These feeding sites are uncommon, produce only a small amount of ripe fruit each day, and are characterized by a high degree of intraspecific fruiting and flowering synchrony. Trees of the same species are frequently visited in succession, and individual feeding sites are revisited several times over the course of 1–2 weeks. This type of foraging pattern occurred during both dry and wet seasons and when exploiting fruit, nectar, legume, and exudate resources. Seasonal variation in the percentage of feeding and foraging time devoted to insectivory was also limited. In this investigation, there was no consistent evidence that temporal changes in overall forest fruit production had a major impact on the feeding, foraging, or ranging behavior of either tamarin species.     

Diet and feeding ecology of saddle-back (Saguinus fuscicollis) and moustached (S. mystax) tamarins in an Amazonian terra firme forest

The feeding ecology of two small-bodied primate species—saddle-back ( Saguinus fuscicollis auilapiresi ) and moustached tamarins ( S. mystax pileatus )—occurring in stable, mixed-species groups was studied in a terra firme forest site in the upper Urucu River, Amazonas, Brazil. Ecological data are based primarily on one mixed-species group of 5–8 saddle-back and 8–10 moustached tamarins. The overall vegetative and animal-prey components of each tamarin species' diet, their selection of food species, and the seasonal variation in their use of plant resources are described, and compared to those of callitrichids elsewhere. The extremely diverse diet of tamarins included at least 136 tree, 33 vine and liana, 12 epiphyte and nine shrub species, as well as a wide range of prey items. They fed primarily on ripe fruit pulp of most of these species for most of the year, but shifted to floral nectar and plant exudates of a few key plant species during the dry season. Taxonomic overlap in plant diet was nearly complete between the two tamarin species, but they diverged considerably in their prey capture techniques. Saddle-backs used the low forest understorey, and manipulatively searched for sedentary prey concealed within discrete, usually rigid, microhabitats, whereas moustached tamarins used the midstorey where they visually searched for mobile prey well exposed on foliage. These and other feeding and foraging patterns are discussed in the light of other callitrichid species studied to date.     

The Effect of Crowding on the Social Behavior of the Cooperatively Breeding Cotton-Top Tamarins (<Emphasis Type="Italic">Saguinus oedipus</Emphasis>)

Several studies show that primates exhibit coping strategies to buffer the effect of increased social tension under crowded conditions. This is the first study to assess the effect of crowding on the social behavior of a cooperative breeding primate. We studied the effect of repeated short-term crowding on the social behavior of 20 cotton-top tamarins (10 breeders, 10 adult–subadult offspring) belonging to 2 large and 3 small groups. We compared scratching and rates of social behavior between 2 conditions: large-outdoor (42.0 m² × 3.3 m) and small-indoor (3.5 m² × 2.2 m) enclosures. Our results indicate that scratching increases in breeders and offspring during crowding. However, whereas the social behavior of breeders in small groups was not affected by crowding, breeders in large groups (n = 4) showed increased rates of severe aggression with their offspring during crowding. Offspring of large groups showed a nonsignificant trend to increase mild aggression, and an increased percentage of time in contact and grooming during crowding. This augmentation of grooming occurred in offspring–breeder dyads and also between offspring. These results suggest that helpers from large groups use coping strategies when social tension increases.     

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.     

Effect of Resting Patterns of Tamarins (<Emphasis Type="BoldItalic">Saguinus fuscicollis</Emphasis> and <Emphasis Type="BoldItalic">Saguinus mystax</Emphasis>) on the Spatial Distribution of Seeds and Seedling Recruitment

The spatial distributions of dispersed seeds have important evolutionary consequences for plants. Repeated defecations in sites frequently used by seed dispersers can result in high seed concentrations. We observed the resting behavior of a mixed-species group of tamarins in Peru and recorded the occurrence of seed dispersal (over 8 mo) and seed fate (over 11–22 mo) to determine whether the location and use of resting sites influenced the spatial distribution of dispersed seeds and seedlings. The tamarins rested mostly on trees (Saguinus fuscicollis: 60.6%, S. mystax: 89.2%) and dead trunks (S. fuscicollis: 24.4%) and used 61% of their resting sites repeatedly. During both the dry and wet seasons, tamarins dispersed significantly more seeds within resting areas (0.00662 and 0.00424 seeds/m², respectively) than outside them (0.00141 and 0.00181 seeds/m²). Seed survival and seedling recruitment did not differ significantly between resting and other areas, resulting in a higher seedling concentration around the resting sites. Seed density did not increase with the duration or the frequency of use of the resting sites but did increase when we pooled the seasonal resting sites together in 50 m × 50 m quadrats, ultimately causing a clumped distribution of dispersed seeds. The use of resting sites in secondary forest, particularly during the dry season, allows the creation of seedling recruitment centers for species coming from the primary forest. Our findings show that tamarin resting behavior affects the spatial distribution of dispersed seeds and seedlings, and their resting sites play an important role in plant diversity maintenance and facilitate forest regeneration in degraded areas.     

Rapid shifting of foraging pattern by Yakushima macaques ( Macaca fuscata yakui ) in response to heavy fruiting of Myrica rubra

We describe short-term changes in foraging behavior by wild Yakushima macaques (Macaca fuscata yakui),which inhabit a warm-temperate broad—leaved forest on Yakushima Island (30°N, 131°E), Japan. Rapid changes of dietary composition, activity budget, and range use by the monkeys occurred from May to June, apparently associated with changes in the availability of the fruit of Myrica rubraBefore the fruit ripened, monkeys spent less time moving and more time feeding on many species of leaves, which accounted for 40% of feeding time. However, when M. rubrabegan to ripen, they fed intensively on the fruit, which accounted for three-fourths of feeding time,though the activity budget remained unaffected As fiuit of M. rubradecreased,the monkeys fed more on the fruit of other species and on insects, and spent more time moving at higher speeds. There marked shifts in foraging pattern occurred within only two months. In terms of moving cost and dietary quality,Yakushima macaques shifted their foraging pattern according to the availability of M. rubrafrom a “low-cost, low-yield” strategy to a “low-cost, high-yield” strategy, and then to a more costly strategy. The ability to make such rapid shifts in foraging pattern may allow the macaques to effectively use the highly variable food supply within their small range.     

Locomotor behavior and feeding ecology of the panamanian tamarin (Saguinus oedipus geoffroyi,callitrichidae, primates)

The Callitrichidae are a family of New World primates that exhibit a complex of behavioral and morphological characters reputedly similar to those of tree squirrels of the genus Sciurus.In particular, the locomotor behavior of tamarins and marmosets has been described as “squirrel-like. ” In this paper I describe a field investigation of the locomotor behavior and ecology of the Panamanian tamarin (Saguinus oedipus geoffroyi)and the redtailed squirrel (Sciurus granatensis).From January through August 1978, a total of 1200 hr was spent observing freeranging populations of tamarins and tree squirrels in an area of secondary forest on the Pacific Coast of Panama. Observations were made using an instantaneous time sampling technique. Individual activity records were collected on focal animals and recorded at 2.5-min intervals throughout the day. The following information was collected: (a) nature and structure of the substrate exploited, (b) activities on these supports and/or types of resources procured, and (c) body posture involved in the use of these supports. Data presented indicate major differences in substrate preference and positional behavior in tamarins and tree squirrels. Unlike squirrels, tamarins avoid vertical and sharply inclined supports during travel. Movements through the canopy is accomplished by a series of long leaps which begin and end on thin terminal supports. However, the Panamanian tamarin spent numerous hours clinging to large vertical trunks while feeding on plant exudate. Gums comprise 23.O% of the noninsect portion of the tamarin diet. The relationships between small body size, claw-like nails, substrate preference, and positional behavior are discussed. Claw-like nails enable this primate to exploit a food resource that would otherwise be inaccessible. The interrelationship between environment, behaviour, and morphology provides a frameworks from which to understand callitrichid adaptations. These adaptations are not convergent with those of the sciurid rodents. An earlier draft of this paper was presented at the 48th Annual Meeting of the American Association of Physical Anthropologists, San Francisco, April 1979.     

The costs of infant carrying in captive cotton-top tamarins

Marmosets and tamarins have a communal rearing system in which all group members help to care for the twin infants characteristic of this family of primates. Helpers are likely to incur time and energy costs by contributing to infant care. Predictions that cotton-top tamarin (Saguinus oedipus) helpers would change their behavior when carrying infants because of reduced mobility and/or a need for increased vigilance were tested in a captive colony. Tamarins carrying an infant spent significantly less time feeding, foraging, moving, or engaging in social activities such as grooming than they did when not carrying. Frequencies of scratching, autogrooming, and scent marking were significantly reduced in carriers, suggesting that their mobility was reduced. However, carriers were significantly less likely to be vigilant (measured by direction of gaze) than when not carrying. Further observations showed that carriers spent more time in concealed areas than they did when not carrying and were probably therefore adopting a cryptic strategy to reduce predation risks to themselves and to infants. These results demonstrate that tamarin helpers pay costs by carrying infants. Some possible compensating benefits are indicated.     

Seed Swallowing in Tamarins: Evidence of a Curative Function or Enhanced Foraging Efficiency?

Nonhuman primates represent a major component of the frugivore biomass in several rain-forest communities. Although there is considerable evidence that prosimians, monkeys, and apes serve as dispersal agents for many tropical trees, little attention has been paid to the more basic questions of why certain species of primates swallow and void seeds, and what, if any, are the advantages to an animal of having a large, hard, bolus pass through its digestive tract. We examine patterns of fruit-eating and seed-swallowing in two species of free-ranging tamarins: Saguinus mystax and Saguinus geoffroyi. Fruits commonly eaten by tamarins contain large seeds surrounded by a fibrous and adhesive pulp or arilate seed coat. They generally swallow seeds and pulp together. Intact seeds are voided over a 1- to 3-h period. Measurements of 132 seeds naturally voided by Panamanian tamarins average 11.2 mm in length and 0.3 g. The greatest number of large seeds contained in the digestive tract of a single animal at one time was 13. In the case of moustached tamarins, we collected 220 seeds. Average seed length is 11.9 mm and average seed weight is 0.3 g. At the time of capture, one animal had 26 seeds in its digestive tract. In both tamarin species, there is evidence of sex-based differences in feeding behavior. Adult female moustached and Panamanian tamarins swallowed and voided seeds of larger size than adult males did. Seed size is positively correlated with pulp weight (p <. 001), therefore females were selecting food items with higher nutritional rewards than adult males did. Given their small body size and relatively short digestive tract, why do tamarins swallow such large seeds? Although several explanations are possible, we propose that the large number and size of undigested seeds continuously passing through the tamarin gut serve a curative role in mechanically dislodging and expelling intestinal parasites—Ancanthocephala (spiny-headed worms)—from their digestive tracts.     

Effects of multiple vertebrate predators on grasshopper habitat selection: trade-offs due to predation risk, foraging, and thermoregulation

Predation risk can influence habitat use and activity of potential prey. I explored how the risk of predation by vertebrates influenced the behavior of grasshoppers. I monitored the height in vegetation and the frequency of resting, moving, and feeding behaviors of both tethered and free-ranging grasshoppers under exposure to various predators. Grasshoppers protected from birds remained high in the vegetation, while those protected only from small mammals and lizards remained low in the vegetation. Grasshoppers exposed to all predators occupied an intermediate height. Lower positions in the vegetation were associated with cooler thermal conditions, lower feeding rates, and lower food availability. My results are consistent with the hypothesis that grasshoppers utilize different microhabitats to balance the trade-off between reducing mortality from predators and experiencing greater food availability, and warmer conditions. This revised version was published online in July 2006 with corrections to the Cover Date.     

Social behavior of wild moustached tamarins,Saguinus mystax,at the Estación Biológica Quebrada Blanco,Peruvian Amazonia

The social behavior in two small, polyandrous groups of moustached tamarins, Saguinus mystax, was studied at the Estación Biológica Quebrada Blanco in northeastern Peru. Allogrooming was the most obvious type of social interaction. Grooming relations were characterized by a strong asymmetry. In both groups, one adult male contributed about 70% of all allogrooming given (in terms of time spent grooming) and allocated his allogrooming evenly to all other group members. Grooming relations between the second adult male and other group members were less intensive. Intragroup agonistic interactions were infrequent, and most of them occurred in the context of feeding on small food resources (fruit, exudate) and during intergroup encounters. Sexual behavior was rare, but at least in one group a tendency existed for the principal groomer to be somewhat more active than the other male. Results are compared with data from other field studies on callitrichid social behavior. Although the label polyandrous correctly describes the demographic structure of many groups, it is not clear whether it is sufficient for understanding the patterning of social relations and thus the social organization of tamarins. © 1996 Wiley-Liss, Inc.     

Separating the effects of prey size and speed on the kinematics of prey capture in the omnivorous lizard Gerrhosaurus major

Feeding behavior is known to be modulated as prey properties change. During prey capture, external prey properties, including size and mobility, are likely some of the most important components in predator–prey interactions. Whereas prey size has been demonstrated to elicit modulation of jaw movements during capture, how prey speed affects the approach and capture of prey remains unknown. We quantified the kinematics associated with movements of both the feeding and locomotor systems during prey capture in a lizard, Gerrhosaurus major, while facing prey differing in size and mobility (newborn mice, grasshoppers, and mealworms). Our data show that the feeding and locomotor systems were recruited differently in response to changes in the size or speed of the prey. The timing of jaw movements and of the positioning of the head are affected by changes in prey size—and speed, to a lesser extent. Changes in prey speed resulted in concomitant changes in the speed of strike and an early and greater elevation of the neck. External prey properties, and prey mobility in particular, are relevant in predator–prey interactions and elicit specific responses in different functional systems.     

Demographic and reproductive patterns in moustached tamarin monkeys (Saguinus mystax): Implications for reconstructing platyrrhine mating systems

In this paper we address a series of questions concerning reproductive opportunities, kinship, dispersal, and mating patterns in free-ranging moustached tamarin monkeys (Saguinus mystax). Between 1980 and 1990 information on group size, composition, and migration patterns was collected on marked groups of moustached tamarins inhabiting Padre Isla, an island in the Amazon Basin of northeastern Peru. In 1990, 86% of 114 animals residing in 16 social groups were trapped, examined, and released. Mean group size was 7.0, including 2.2 adult males and 2.0 adult females. None of these groups was characterized by a single adult male-female pair. In groups with more than one adult female, only the oldest female produced offspring. An examination of dispersal patterns indicates that transfers between groups were common and fell into several categories, including immigration of individual males and females, simultaneous transfer of pairs of subadult and/or adult males (sometimes relatives) into the same social groups, and group fissioning in which males and females of the splinter group join another small social group. We have no unambiguous cases of 2 adult/subadult females migrating together into the same social group. All 6 groups for which reproductive data were available were characterized by either a polyandrous or polygynous (polygyandrous) mating pattern. The results of this study indicate that moustached tamarins reside in small multimale multifemale groups that are likely to contain both related and unrelated adult group members. Kinship and social ties among males appear to be stronger and more longlasting than kinship and social ties among females. We contend that the modal mating system of moustached and many other tamarins is not monogamous, and offer the possibility that cooperative infant care and mating system flexibility in callitrichines evolved from a polygynous mating pattern. © 1993 Wiley-Liss, Inc.     

Enclosure environment affects the activity budgets of captive Japanese macaques (Macaca fuscata)

Individuals adapt to changes in their environment, such as food availability and temperature, by adjusting the amount of time spent in different behavioral activities. These adjustments in behavior should vary across age-sex class according to specific physiological and social needs. We studied the activity budgets of three social Japanese macaque groups inhabiting either vegetated or nonvegetated enclosures in order to compare the effects of access with vegetation, as both food and substrate on resting, feeding, grooming and moving activities over a 12-month period. Daily access to natural foods for monkeys in the vegetated enclosure seems to be largely responsible for the differences in daily time budgets of these three groups. Resting time in all three groups was longer than the time devoted to other activities. Resting and moving time in the two nonvegetated enclosures was significantly longer than in the vegetated enclosure. In contrast, feeding and grooming time was significantly longer in the vegetated enclosure. Seasonal variation in time spent feeding, resting and grooming was significantly effected by enclosure type. In all three enclosures, immatures, particularly females, spent more time feeding and moving, whereas adults spent more time resting. Significant monthly variation in time spent by age-sex class was noted only for feeding and resting. Interestingly, in the vegetated enclosure, time spent feeding on natural vegetation was equal to the amount of time spent feeding on provisioned food. This suggests that factors other than energetic and nutritional needs may be important determinants of the activity budget of the species. These results have important implications for the enrichment of captive primates and our understanding of the maintenance of activity patterns by primates in the wild.     

Leaders of progressions in wild mixed-species troops of saddleback (Saguinus fuscicollis) and mustached tamarins (S. mystax), with emphasis on color vision and sex

Leadership of travel progression is an important aspect of group living. It is widely believed that trichromacy evolved to facilitate the detection and selection of fruit in the dappled light of a forest. Further, it has been proposed that in New World primate species, which typically contain a range of color vision phenotypes, at least one female in a group will be trichromatic (i.e., having three types of visual pigment, in contrast to the two types of pigment found in dichromatic individuals) and will lead the group to fruiting trees. We examine progression leadership within two wild mixed-species troops of saddleback (Saguinus fuscicollis) and mustached (Saguinus mystax) tamarins over a complete year. As whole units, the mixed-species troops were most frequently led by a mustached tamarin. This is the first time that mixed-species group leadership and individual leadership have been quantified in these tamarin species. In terms of single-species intragroup leadership, neither the visual status (dichromatic or trichromatic) nor the sex of individuals had a consistent effect across species. Saddleback tamarin groups were led by males more frequently than females, while evidence suggests that mustached tamarins may be female-led. The notion that all groups contain at least one trichromatic female that leads the troop to feeding trees was not supported.     

Habitat Exploitation by Free-ranging Saguinus niger in Eastern Amazonia

We monitored the foraging behavior of the members of a group of black-handed tamarins (Saguinus niger) at a site in eastern Amazonia. Their diet was frugivorous-insectivorous, but also included pod exudate of Parkia pendula. The focal group used all 3 types of forest—primary, logged, and secondary— in all months, but differentially between seasons. In the dry season, tamarins spent more than half of activity time in primary forest and less than a third in secondary forest whereas during the wet season, the proportions were reversed. Data on resource abundance indicated that the shift in habitat preference is related to a seasonal change in the distribution of fruit sources, with a larger number of species and individuals fruiting during the wet season. We recorded no such variation in the abundance of arthropods. While using a larger area, including more secondary forest, during the wet season, the group traveled significantly shorter distances each day, reflecting the availability of a larger number of fruit sources. Overall, the results reemphasize the ecological and behavioral flexibility of Saguinus niger and their ability to cope with habitat disturbance.     

Habitat,diet, and activity patterns of free-ranging woolly spider monkeys (Brachyteles arachnoides E. Geoffroy 1806)

Results of a 10-month study of the ecology and behavior of free- ranging woolly spider monkeys (Brachyteles arachnoides)in Brazil show that these animals are strongly folivorous. Leaf-eating accounted for more than 50% of the total feeding time in all samples but one and accounted for more than 80% of the total feeding time in three samples. Mature foliage was routinely eaten. Woolly spider monkeys consistently spend more than 50% of each day quietly resting and sleeping. Animals travel little except when actively feeding and show low levels of social interaction. Such an activity profile suggests that woolly spider monkeys may often be living near the limits of their energetic resources. The social organization of the species is unusual for a folivorous primate in that small groups of females and associated immature animals confine their activities to discrete home-range areas, whereas males are itinerant, traveling over the home ranges of various female groups. Animals sharing a common home-range area show no permanent daily pattern of association other than that of mother-dependent offspring. Foraging alone or with few conspecifics should maximize each individual’s returns from foraging by minimizing the day range that must be traveled each day to locate foods while simultaneously lowering interference competition for higher-quality dietary resources.