Primate Studies

Dietary preferences of white-faced capuchins monkeys (C. capucinus) in northwestern Costa Rica were examined across age classes and between two distinct seasons over the course of 1 year. The findings show that the dietary profiles of small juveniles, large juveniles, and adults are quite similar, suggesting that juveniles are efficient foragers from a young age. The predictions of several ontogenetic models are presented, and the data lend limited support to the juvenile risk aversion and motor ability models.

The bushmeat trade represents a serious threat to the ape populations of Africa. This paper examines the multiple facets of the bushmeat trade: what it consists of, its consequences, and its many other dimensions. The purpose of this assessment is to provide evidence in support of the argument that the bushmeat trade has severely impacted African ape populations and has negatively affected the distribution, population sizes, and overall livelihood of these primates. With a focus on the chimpanzee (Pan troglodytes), this paper will offer a critical evaluation of this evidence and explore potential remedies and their effectiveness toward this threat.

Nonhuman primates with high behavioral and dietary plasticity have a greater chance of survival in an ever-changing environment. This paper examines the multiple facets of species and habitat variation in activity profiles among Cebus capucinus and Alouatta palliata populations in Costa Rica and Nicaragua. Comparisons will encompass the frequency of resting periods, moving and travelling behaviors, foraging activity, and feeding in two species of New World Monkeys living together in two, very different ecosystems (a tropical rainforest and a seasonal, dry forest). The purpose of this assessment is to provide a better understanding of the activity profiles in which these primates navigate their daily routines and meet their dietary needs and overall livelihood. With a focus on the free-ranging populations of White-Faced Capuchin Monkeys (Cebus capucinus) and Black-Mantled Howler Monkeys (Alouatta palliata) at La Suerte Biological Field Station in Northeastern Costa Rica and Ometepe Biological Field Station in Nicaragua, this paper will provide an evaluation of the activity profiles and strategies of these coexistent populations and explore possible ecological and behavioral differences.

The two failed orientations to kinship, nurture and fitness, are transcended as this collection of original kinship work moves forward, building on the rich theoretical and ethnographic past of kinship study to a reinvigorated future of new data, reconceptualization of paradigms, fresh debates and new theory. Using kinship to anthropomorphize nonhuman primates is rejected. Contributions from 18 distinguished scholars of kinship cover the four-field, cross-cultural science of anthropology. Issues in kinship study are explored through marriage, kin terms, space, incorporation, ritual, primate studies, and contributions from Russia. This collection carries kinship study into the future.

Mastication causes distinct use wear scars on teeth that can aid in dietary reconstructions of fossils. However, the role played by exogenous grit in dental wear complicates the association between wear and diet. Dental wear analyses often assume that foods closer to the soil contain more exogenous grit than those in the forest canopy. Yet, a layer of leaf litter covering many forest floors may trap grit from the soil, keeping it from settling on surrounding vegetation or becoming part of atmospheric dust. Cercocebus atys is frequently referenced in dental wear studies because of its dependence on hard Sacoglottis gabonensis seeds collected from the forest floor. Here we examine quantities of dust deposition at different forest levels and assess its potential role in wear patterns observed in C. atys. We collected grit from S. gabonensis seeds (N = 64) found under the leaf litter and compared them to grit samples taken from the surface of leaves at different forest strata (N = 450) in Ivory Coast's Taï National Park. Seeds underneath the leaf litter were coated with significantly more grit than leaves above the leaf material and we conclude that leaf litter is a significant barrier to grit particles originating from the soil. Given that evidence points to a significant difference in grit amount between foodstuffs on the ground and foods near the ground, the findings lead to a prediction of differences in dental wear patterns between purely arboreal foragers and those incorporating terrestrial food sources.

One theory about comedy is that the stand-up comedian is always engaged in a quest for " respectability. " As the center of attention, the comedian has a unique opportunity to share specific truths with authority, but at the same time, the comedian engages in self-deprecation and being an occasional butt of their own joke. In Elmer Blistein's classic book Comedy in Action (1964), he relates a story about Danny Kaye. When Kaye's five-year-old daughter saw him perform in a nightclub, he noticed her crying and asked her what was wrong. She replied, " I don't like people to laugh at my Daddy " (Blistein 1964: 17). Kaye's daughter was struggling with the difference between " laughing at " and " laughing with. " The comedian constantly negotiates being the butt of the joke who is the object of laughter, and being the expert who is in control of the performance and laughing with the audience. In either case, neurobiological analysis of laughter shows striking differences in types of laughter and the active locations of the brain in functional magnetic resonance imaging (fMRI) scans. One research team has documented a " laughter neural network " showing that joyous and taunting laughter each produced different connectivity patterns in parts of the brain involved in sound association, thinking and visual imagery. The fact that laughter occurs in a social context where roles and statuses between individuals are interpreted and reinterpreted is very important. Complex social laughter is used in a conscious and goal-directed manner to influence and modify the attitudes and behaviors of those around us. " Polite laughter " as a way to acknowledge things that members of a group all find funny can reinforce social communication and cooperation. Researchers have documented this behavior among great apes and chimpanzees. Phenomenologically, the frequency and pitch of laughter produced in different social settings can vary widely in accordance with the emotional state of the laugher, with the difference in pitch between joyous laughter and taunting " schadenfreude " laughter at another's misfortune showing distinct differences. The social context of laughter and its neurobiological basis is central to the distinction between laughing at someone and laughing with someone.

Uner Tan was born in Unye, Ordu in Turkey on 1 May 1937 and attended high school in Izmir Turkey, followed by medical school at the Egean University in Izmir. He moved to Germany to attend Goettingen University, where he earned his medical doctorate. He received his PhD from the Max-Planck Institute for Medical Research in Goettingen.

Tan returned to Turkey in 1969 and worked as lecturer and then associate professor at Hacettepe and Ataturk universities in Turkey. He was head of the Department of Physiology at Ataturk University from 1973 to 1999 and BlackSea Technical University until 2002. He was head of the Neurophysiology Unit at Cukurova University in Adana until 2004. He remains at Cukurova University as senior researcher.

Tan’s many research interests include the spinal and cerebral motor systems, epilepsy, sex differences in cerebral lateralization and cognition, and Uner Tan Syndrome, which involves habitual quadrupedalism. Tan’s publications include around 180 papers in the Science Citation Index and almost 2000 citations since 1966.

Tan’s memberships include the American Academy of Neuropsychology, World Innovation Foundation, the American Psychological Association and Honorary Membership of the Turkish Academy of Sciences. Tan also belongs to the New York Academy of Sciences, the European Neuroscience Association, and several other professional associations.

Tan has served as editor or member of editorial boards for journals such as the International Journal of Neuroscience and Perceptual and Motor Skills. He is currently on the editorial board of the Journal of Neuroquantology, and acts as reviewer for various scientific periodicals.

Tan has won many awards, including Turkish awards such as the Dorothea Morton First Prize for Neurological Sciences (1980) and Science award from Turkish Technical and Scientific Council. His USA awards include Einstein Medals for Science and Peace (1986), Medal of Honor (1987), and Nobel Medals for Science and Peace (1991).

Uner Tan is married with four children. His hobbies include playing the violin (he was once first violinist), and stamp collecting.

In Brazil, the destruction of the Atlantic forest and the Caatinga dry forest continues to the present, having a profound effect on the non-human primates. Here we present data on abundance of the critically endangered Callicebus barbarabrownae (Pitheciidae), the only primate endemic to the Caatinga, and evaluate if human presence impacts their distribution. We conducted over 152 km of line transect surveys, mostly in semi-deciduous forest near the Chapada Diamantina National Park, NE Brazil. The blond titi monkey occurred at an extremely low abundance, even when considering calls their abundance was lower than that reported for closely related species in different Atlantic forest areas surveyed previously. Although hunting pressure is high in the area, the reasons for their lower abundance are yet unclear. The presence of taller and relatively undisturbed forest seemed key factors for the presence of the species even in areas with heavy human presence. We speculate that they could prefer wetter habitats and gallery forests. Our results are the first record of blond titi monkey in protected area. The long term survival of this critically endangered species may depend on increasing the number of conservation units and stimulating conservation awareness in the local human population. Resumen En Brasil, la destrucción del bosque Atlántico y el bosque seco de Caatinga continua actualmente, ejerciendo un pro-fundo efecto sobre los primates no humanos. Presentamos datos de abundancia del críticamente amenazado Callicebus barbarabrownae (Pitheciidae), el único primate endémico de la Caatinga, y evaluamos si la presencia humana impacta su distribución. Llevamos a cabo 152 km de evaluaciones por transectos lineares, principalmente en bosque semideciduo cerca del Parque Nacional Chapada Diamantina, al nororiente de Brasil. La abundancia del mono titi rubio es extremadamente baja, aun cuando se consideraron las vocalizaciones su abundancia fue más baja que la reportada para especies cercanamente relacionadas en diferentes áreas del bosque Atlántico evaluadas previamente. Aunque la presión de caza es alta en el área, las razones para de su baja abundancia no son claras aún. La presencia de bosque más alto y relativamente no perturbado parecen ser factores clave para la presencia de la especie aún en áreas con alta presencia humana. Especulamos que la especie podría preferir habitats más húmedos y bosques de galería. Nuestros resultados son el primer registro del mono titi rubio en un área protegida. La sobrevivencia a largo plazo de esta especie críticamente amenazada puede depender de incrementar el número de unidades de conservación y de estimular en la población humana local conciencia por su conservación. Palabras clave: Bosque Atlántico; mono titi rubio; conservación; bosque intervenido; cacería.

We studied the choice behavior of 2 monkeys in a discrete-trial task with reinforcement contingencies similar to those Herrnstein (1961) used when he described the matching law. In each session, the monkeys experienced blocks of discrete trials at different relative-reinforcer frequencies or magnitudes with unsignalled transitions between the blocks. Steady-state data following adjustment to each transition were well characterized by the generalized matching law; response ratios undermatched reinforcer frequency ratios but matched reinforcer magnitude ratios. We modelled response-by-response behavior with linear models that used past reinforcers as well as past choices to predict the monkeys' choices on each trial. We found that more recently obtained reinforcers more strongly influenced choice behavior. Perhaps surprisingly, we also found that the monkeys' actions were influenced by the pattern of their own past choices. It was necessary to incorporate both past reinforcers and past choices in order to accurately capture steady-state behavior as well as the fluctuations during block transitions and the response-by-response patterns of behavior. Our results suggest that simple reinforcement learning models must account for the effects of past choices to accurately characterize behavior in this task, and that models with these properties provide a conceptual tool for studying how both past reinforcers and past choices are integrated by the neural systems that generate behavior.

Female rhesus macaques exhibit matrilineal dominance structures and high dominance rank confers fitness benefits across a lifetime and across generations. Rank effects are ‘inherited’ through social processes that are well understood; however, biological mechanisms that might impact these processes are not well known. Recently it has been shown that prenatal androgens appear to be implicated in supporting dominance rank hierarchies in some mammals. In humans, inter-individual differences in the 2nd (index) to 4th (ring) digit ratio (2D:4D) have been linked indirectly to variation in prenatal androgen effects (PAE), with low 2D:4D in both sexes associated with higher inferred PAE. 2D:4D has also been related to dominant social behavior and has been shown to co-vary with social systems across non-human primate species. Here we investigate how 2D:4D co-varies with socially inherited dominance rank in female rhesus macaques. Low 2D:4D was associated with higher ranking females, while higher 2D:4D was associated with lower ranking females. Similar relationships were also shown between ranked families within matrilines. 2D:4D evidence suggests that variation in PAE may be involved in the maintenance of female dominance rank relationships in cercopithecine primates.

The study was oriented to inventory and evaluation of primates and identify threats to their populations in
montane forest of the Region Huánuco, an area little explored with respect to wildlife. From June to July and
September to October 2014 transect censuses were conducted in sampling points corresponding to the
micro-basins of the Chontayacu and Chinchao rivers and high basin of the Huallaga River. In 618 km of
travel length were recorded 47 groups belonging to five species were recorded, being the most common
Alouatta seniculus (15 groups) and Lagothrix flavicauda (13 groups). L. flavicauda was observed only in the
micro-basins of the Chontayacu River and Ateles chamek in the high of the Huallaga River. In the study
area, these primates live in patches of primary and residual forest, except in Chontayacu where the forest is
still dense and extensive. Population density was highest for L. flavicauda (20.8 indiv./km2) and lowest for
Sapajus macrocephalus (2.7 indiv./km2). Between the observed activities, the deforestation for agriculture
and cattle raising is the major threat to the survival of primates, particularly in the micro-watershed of the
Chinchao River and high watershed of the Huallaga River.
Keywords: Region Huánuco, mountain forest, primate diversity, population density, threats.

The study was conducted from November’2018 to April’2019 to know the Mortality Pattern of Rhesus Macaque at
Basistha Temple Kamrup district of Assam. During the whole survey it has been found that among the groups of Rhesus macaque
in Basistha Temple the mortality cases are very frequent. As our survey reports presenting the macaques are mostly injured due to
Accident that is 63%. Accidents occur due to playing on the electricity poles, beaten by human, during playing and by Vehicles in
the temple premise. The macaques are suffered from a lot of Viral, Bacterial & fungal infections. An around 32% percent case has
been found where these macaques are suffered because of infections as reported. During the survey from September 2018 to April
2019 around 5% cases of Death has been found. The deaths occurred due to disease, accidents, vehicular accidents, electrocution
and beaten up by human have been found.

Danny Lozano When first introduced to the idea of primate observation and the fact that we as modern day humans might have evolved from such simple species, I have to admit that I was very intrigued. My first thoughts were, " what can I learn from primates and I wonder if I will observe anything spectacular while at the Zoo? ". What I found surprised and amazed me at how these primates were so human-like and so capable of figuring out things. Out of all the species of Primates that the San Diego Zoo had on display, I was drawn to a few in particular: the Squirrel Monkey, the Francois' Langur, the Orangutans, and Siamangs. Though others may feel that primates are not very intelligent, through observation it is clear that primates are a very intelligent and curious species. The Squirrel Monkey, or the Saimiri Sciureus, from South America, was one of the more interesting and fun primates to watch. This New World Monkey ranges from about 25-35 cm and a tail about 35-42 cm. These monkeys had light hair on their faces, brown hair on their bodies and large black eyes. The Male was slightly larger than the female, sexual dimorphism, and was the only one in the exhibit because. I found this interesting because the Squirrel Monkeys " live together in multi-male/multi-female groups… " (Wikipedia 2009:01) Tiny in size, these monkeys really enjoyed running around their exhibit and attracted quite a large audience. Their tails, though not prehensile, are used primarily " as a kind of 'balancing pole' and also as a tool. " (Wikipedia 2009:01) Meaning that they are able to move with agility and speed while maintaining their balance on small and large branches. I feel they attracted so many people because they were able to jump through the branches and use the ropes that are in their exhibit to help brachiat, using arms to swing from branch to branch, through the air and catch other branches to continue moving. This is a type of intelligence that I feel the Squirrel Monkey demonstrates. The squirrel monkey, along with all primates, have what is called binocular stereoscopic vision, meaning they have " overlapping fields of vision, with both sides of the brain receiving images from both eyes ". (Relethford 2008:136) This provides depth perception which is very important in a three dimensional world and for moving quickly and safely through it. This ability to process information quickly shows that the Squirrel Monkey is not just a fun-loving primate but, an intelligent primate who is able to move quickly through the trees, process everything quickly, and stay safe. Another species of primates observed was the Fancois' Langur. This is an Old World Monkey also known as Trachypithecus Francoisi, which inhabits China. These monkeys were extremely interesting to watch and I thoroughly enjoyed being around them. They are a bit larger than the Squirrel Monkeys, about 2-3 ft long with black hair and small white patches on their cheeks. There were two males and two females in the exhibit and they are, unfortunately, an endangered species due to deforestation. These monkeys had one of the largest exhibits for the monkeys, with two trees that are very tall, so that they could have room to run and climb very quickly. They are quick and agile and seemed to enjoy interaction with one another. There was a bit of sexual dimorphism, the males were slightly larger than the females and were slightly more relaxed. The females, though smaller than the males, had more color in their faces and were a bit more active. A very intelligent and interesting primate to observe was the Orangutan, a Greater Ape. Orangutan, or Pongo Pygmaeus, " translates from Malay as " man of the forest " and they are found in Indonesia ". (Relethford 2008:175) There were 3 Orangutans in the exhibit, one male and two females. There are a few obvious sexual dimorphisms between the males and females. For one, the males are considerably larger than the females, about twice the size, and the males " have large pads of fat on their faces " (Relethford 2008:175) which make it easy to distinguish between the two. One thing that stands out about the Orangutans is that they have reddish brown hair. These arboreal primates are agile climbers and hangers. They would use both arms and legs to move around. Though there was not much for them to climb on or hang from, the exhibit had a lot of posts with food on top of them, so that the Orangutans would have to figure out how to get them. There was a female Orangutan who, after getting a piece of fruit, sat on one of the structures and enjoyed her " prize ". There was no possible way to observe her at such a distance but, I decided to stay for a minute longer and watch. Molly, the Orangutan that I named, dropped her piece of fruit and climbed down from where she was sitting, walked over to me and sat right in front of me on the other side of the glass. Molly while sitting in front of me put both of her hands up on the glass as if to touch my face, social interaction. Her intelligence and curiosity became apparent when I was writing notes to myself on my observations. Molly would try to see what I was writing and would put her hand to her chin, in the " thinking position " , and would scratch her head. I was very impressed and shocked at how curious she was. Through curiosity comes intelligence through wanting to learn more, the more learned the more intelligent one becomes. Though Molly may not have been able to fully understanding what I was doing their or fully understand what I was writing, I feel that she knew I was watching her and what ever I was doing was somehow related to her. Due to the fact that there were no Prosimians at the San Diego Zoo, the Siamangs were another species of Apes to observe. The Siamangs, Lesser Apes, are arboreal with dark black hair and long arms and are found primarily in Indonesia. These apes tend to be very brachiat and more around very quickly. The sexual dimorphism was with the " males being slightly larger than the females ". (Gron 2008:01) One thing that makes the Siamangs stand out from other primates, more specifically Apes, is their large inflatable throat sac. The " throat pouch can be inflated to the size of its head, allowing the Siamang to make loud resonating calls or songs " (Wikipedia 2009:01). As a music major, it was interesting to hear and see this primate with the ability to enlarge his throat and make such a loud and wonderful sound. A technique used in music, to allow for a more resonate sound when singing, is to open your throat to allow for

Abstract: We report on the current status and threats to Lagothrix flavicauda and other primates that inhabit montane forest of the Región Huánuco; an area that has been little explored with regard to its primate fauna and other mammals. During 618 km of transect walks in June–July 2014 and September–October 2014, we encountered 47 groups of five primate species, the most common being Alouatta seniculus (15 groups) and Lagothrix flavicauda (13 groups). We also observed four groups of Aotus sp. in the Miraflores census site. Lagothrix flavicauda was seen only in the microbasin of the Río Chontayacu, and Ateles chamek in the upper Río Huallaga. The primates were living in patches of primary and remnant forest surrounded by farmland and pasture except in Chontayacu, where the forest is still dense and extensive. Of the three species with complete counts, group sizes were largest for L. flavicauda (mean 13.6 ±7.8, n = 5) and smallest for A. seniculus (mean 5 ±3.5, n = 11). Population densities were highest for L. flavicauda (20.8 ind./km²) and lowest for Sapajus macrocephalus (2.7 ind./km²). Deforestation for agriculture and cattle ranching and hunting are the major threats to the survival of these primates. Sapajus macrocephalus and Cebus yuracus were the most affected by these threats, particularly in the Río Chinchao microbasin,
Key words: Primates, Andean montane forest, Lagothrix flavicauda, threats

This study presents a pilot survey of the avahis
(pair-living, nocturnal prosimians) living in threatened littoral forest fragments of southeastern Madagascar. In the
period of October–December 2004, I evaluated the density
of adult and newborn avahis (carried by the mothers) by
counting the individuals encountered during 58 night walks
in seven fragments of Sainte Luce and Mandena forests,
along one trail/fragment. Along each trail, I used random
plots (5 m
2
) for a preliminary characterization of the vegetation. The density of the population was not correlated
with fragment size and number of plant morphospecies,
while it was correlated with large tree availability. Possibly
due to a low energy diet based on leaves and to specialized
and energetically expensive vertical leaping, the loss of
large trees by selective logging seems to affect avahi
populations more than other variables.

A committee of field primatologists representing major primatological societies and organizations from Africa, Asia, Europe, and North, Central, and South America have crafted a "code of best practices" to help field primatologists navigate the contemporary ethical landscape.

Gorillas living in western central Africa (Gorilla gorilla) are morphologically and genetically distinguishable from those living in eastern central Africa (Gorilla beringei). Genomic analyses show eastern gorillas experienced a significant reduction in population size during the Pleistocene subsequent to geographical isolation from their western counterparts. However, how these results relate more specifically to the recent biogeographical and evolutionary history of eastern gorillas remains poorly understood. Here we show that two rare morphological traits are present in the hands and feet of both eastern gorilla subspecies at strikingly high frequencies (>60% in G. b. graueri; ∼28% in G. b. beringei) in comparison with western gorillas (<1%). The intrageneric distribution of these rare traits suggests that they became common among eastern gorillas after diverging from their western relatives during the early to middle Pleistocene. The extremely high frequencies observed among grauer gorillas-which currently occupy a geographic range more than ten times the size of that of mountain gorillas-imply that grauers originated relatively recently from a small founding population of eastern gorillas. Current paleoenvironmental, geological, and biogeographical evidence supports the hypothesis that a small group of eastern gorillas likely dispersed westward from the Virungas into present-day grauer range in the highlands just north of Lake Kivu, either immediately before or directly after the Younger Dryas interval. We propose that as the lowland forests of central Africa expanded rapidly during the early Holocene, they became connected with the expanding highland forests along the Albertine Rift and enabled the descendants of this small group to widely disperse. The descendant populations significantly expanded their geographic range and population numbers relative to the gorillas of the Virunga Mountains and the Bwindi-Impenetrable Forest, ultimately resulting in the grauer gorilla subspecies recognized today. This founder-effect hypothesis offers some optimism for modern conservation efforts to save critically endangered eastern gorillas from extinction. Am J Phys Anthropol 159:S4-S18, 2016. © 2016 Wiley Periodicals, Inc.

Gorillas living in western central Africa (Gorilla gorilla) are morphologically and genetically distinguishable from those living in eastern central Africa (Gorilla beringei). Genomic analyses show eastern gorillas experienced a significant reduction in population size during the Pleistocene subsequent to geographical isolation from their western counterparts. However, how these results relate more specifically to the recent biogeographical and evolutionary history of eastern gorillas remains poorly understood. Here we show that two rare morphological traits are present in the hands and feet of both eastern gorilla subspecies at strikingly high frequencies (>60% in G. b. graueri; ∼28% in G. b. beringei) in comparison with western gorillas (<1%). The intrageneric distribution of these rare traits suggests that they became common among eastern gorillas after diverging from their western relatives during the early to middle Pleistocene. The extremely high frequencies observed among grauer gorillas-which currently occupy a geographic range more than ten times the size of that of mountain gorillas-imply that grauers originated relatively recently from a small founding population of eastern gorillas. Current paleoenvironmental, geological, and biogeographical evidence supports the hypothesis that a small group of eastern gorillas likely dispersed westward from the Virungas into present-day grauer range in the highlands just north of Lake Kivu, either immediately before or directly after the Younger Dryas interval. We propose that as the lowland forests of central Africa expanded rapidly during the early Holocene, they became connected with the expanding highland forests along the Albertine Rift and enabled the descendants of this small group to widely disperse. The descendant populations significantly expanded their geographic range and population numbers relative to the gorillas of the Virunga Mountains and the Bwindi-Impenetrable Forest, ultimately resulting in the grauer gorilla subspecies recognized today. This founder-effect hypothesis offers some optimism for modern conservation efforts to save critically endangered eastern gorillas from extinction. Am J Phys Anthropol 159:S4-S18, 2016. © 2016 Wiley Periodicals, Inc.

Studies of the shoulder girdle are in most cases restricted to morphological comparisons and rarely aim at elucidating function in a strictly biomechanical sense. To fill this gap, we investigated the basic functional conditions that occur in the shoulder joint and shoulder girdle of primates by means of mechanics. Because most of nonhuman primate locomotion is essentially quadrupedal walking—although on very variable substrates—our analysis started with quadrupedal postures. We identified the mechanical situation at the beginning, middle, and end of the load-bearing stance phase by constructing force parallelograms in the shoulder joint and the scapulo-thoracal connection. The resulting postulates concerning muscle activities are in agreement with electromyographical data in the literature. We determined the magnitude and directions of the internal forces and explored mechanically optimal shapes of proximal humerus, scapula, and clavicula using the Finite Element Method. Next we considered mechanical functions other than quadrupedal walking, such as suspension and brachiation. Quadrupedal walking entails muscle activities and joint forces that require a long scapula, the cranial margin of which has about the same length as the axillary margin. Loading of the hand in positions above the head and suspensory behaviors lead to force flows along the axillary margin and so necessitate a scapula with an extended axillary and a shorter cranial margin. In all cases, the facies glenoidalis is nearly normal to the calculated joint forces. In anterior view, terrestrial monkeys chose a direction of the ground reaction force requiring (moderate) activity of the abductors of the shoulder joint, whereas more arboreal monkeys prefer postures that necessitate activity of the adductors of the forelimb even when walking along branches. The same adducting and retracting muscles are recruited in various forms of suspension. As a mechanical consequence, the scapula is in a more frontal, rather than parasagittal, position on the thorax. In both forms of locomotion—quadrupedal walking and suspension—the compression-resistant clavicula contributes to keeping the shoulder complex distant from the rib cage. Future studies should consider the consequences for thorax shape. The morphological specializations of all Hominoidea match the functional requirements of suspensory behavior. The knowledge of mechanical functions allows an improved interpretation of fossils beyond morphological similarity.