Search

Information on the positional behaviors of primates is essential for understanding the mechanisms of environmental adaptation. From October 2021 to September 2022, we collected data on positional behaviors of Assamese macaques (Macaca assamensis) at Guangxi Nonggang National Nature Reserve, China, using instantaneous scan sampling method. Our results showed that quadrupedal walking (34.99% ± 6.05%) was adopted as their most frequent locomotor mode, followed by leaping (31.54% ± 10.50%), climbing (25.55% ± 11.33%), quadrupedal running (6.55% ± 2.65%) and bridging (1.37% ± 1.19%). The ground (36.83% ± 21.18%) was the most frequently used stratum during moving. Most arboreal locomotion occurred on small (44.06% ± 11.36%) and medium (34.90% ± 11.09%) sized substrates. Sitting (81.19% ± 10.47%) was used as their most common postures, followed by holding (6.38% ± 9.97%), quadrupedal standing (3.70% ± 3.03%), bipedal standing (3.54% ± 1.84%), sprawling (3.17% ± 6.45%), suspending (1.88% ± 1.19%) and lying (0.14% ± 0.21%). Positional behaviors seasonally vary with habitat structure, and distribution of food resources. The macaques used climbing more frequently in the fruit-lean season (dry season) than in the fruit-rich season (rainy season), which could be related to reducing energy expenditure in the dry season. In addition, they adopted holding and lying together to conserve energy and stabilize intergroup relationships. In conclusion, Assamese macaques adapt to limestone forests with positional behavior flexibility in response to seasonality. Our findings highlight the necessity to understand the effects of ecological factors on the behavioral ecology and adaptations of Assamese macaques in their unique limestone forest habitats. [ABSTRACT FROM AUTHOR]

Studying positional behaviors is important for understanding how animals interact with their immediate environment. This is particularly important in arboreal species since arboreal milieus are primarily characterized by three‐dimensional problems that arboreal species must overcome to efficiently access resources. Similarly, a fundamental aspect of an animal's ecology is its daily activity pattern. This information is important for understanding the basic ecology of animal species and their eco‐evolutionary dynamics. This study sought to understand the habitat use and nocturnal lifestyle of the highly arboreal kinkajou (Potos flavus) by documenting variation in positional behaviors and activity patterns using 2223 photographs obtained from 27 camera traps in French Guiana. Data were analyzed using descriptive statistics, Kernel density estimation (KDE), and Gantt charts. Our results indicate that kinkajous show a strictly nocturnal activity pattern beginning from 19:00 h to 05:57 h, with peak active periods between 01:00 h and 02:00 h. The most frequent activities were scanning (48.33%) and traveling (47.13%). Quadrupedal walking (95.43%) was the main locomotor behavior during traveling. However, when crossing gaps between two substrates, kinkajous would either bridge (42.22%), leap (33.33%), or drop (26.67%) across gaps. Inactive periods were characterized by grooming (77.32%) and resting (27.84%) while mostly assuming a sitting (90.67%) or a catlike body curl posture (92.59%), interchangeably. This study highlights the broad array of positional behaviors displayed by kinkajous, further providing information to understand its basic ecology and eco‐evolutionary dynamics. [ABSTRACT FROM AUTHOR]

Abstract Information on positional behavior contributes to the understanding of the ecological adaptation mechanisms in animals. We collected data on the positional behavior of white‐headed langurs (Trachypithecus leucocephalus) at the Guangxi Chongzuo White‐Headed Langur National Nature Reserve from September 2016 to August 2017 via instantaneous scan sampling method. This study aimed to examine the importance of positional behavior flexibility in limestone forests characterized by seasonal variations in climate and food resources. Our results indicated that langurs adopted leaping (47.92% ± 5.50%) and vertical climbing (40.13% ± 6.20%) as their predominant locomotor modes and sitting (83.08% ± 4.70%) as their predominant posture. Their positional behavior exhibited marked seasonal variations. More specifically, langurs used quadrupedal walking more frequently during the dry season than during the rainy months. In the stationary state, they sat more frequently during the dry season, whereas they laid and suspended more often during the rainy season. Their positional behavior was affected by fruit availability, day length, and temperature. Quadrupedal walking increased with the decrease in fruit availability, whereas leaping was positively correlated with fruit availability. Moreover, sitting was positively correlated with average temperature but negatively correlated with day length. Lying was also negatively correlated with temperature but positively correlated with day length. We conclude that white‐headed langurs adapt to limestone forests with positional behavior flexibility in response to seasonality. Our research provides evidence of the effects of food availability, ambient temperature, and day length on the positional behavior of white‐headed langurs, highlighting the need to understand their behavioral ecology and the influence of ecological factors on behavioral adaptation.

Our understanding of how bipedalism evolved in hominins has been refined through studies of bipedal behavior in non-human primates, both in the wild and in the laboratory. Bipedal behavior in non-human primates makes up a relatively small portion of their behavioral repertoire. Understanding when bipedal behaviors occur and how bipedal behaviors emerge can provide further insight into the context in which bipedal behaviors may have evolved. Here, we examine age-related variation in bipedal behavior in wild bearded capuchins (Sapajus libidinosus). 2,209 records of bipedal posture and locomotion, activity state, and substrate used during bipedal behavior (17.2% of all records of positional behavior) were examined for individuals ranging from 3 months to 15 years or older in two groups (32 individuals in total). Apart from very young individuals that were carried by older conspecifics, individuals of all ages showed similar rates and patterns of bipedal behaviors. Bipedal postures were used predominantly during feeding and foraging, most often in arboreal settings, and most often with their prehensile tail grasping, or in contact with, the substrate. Bipedal locomotion occurred most often on terrestrial substrates and comprised only 3% of all records of bipedal behavior.

Information on positional behavior contributes to the understanding of the ecological adaptation mechanisms in animals. We collected data on the positional behavior of white‐headed langurs (Trachypithecus leucocephalus) at the Guangxi Chongzuo White‐Headed Langur National Nature Reserve from September 2016 to August 2017 via instantaneous scan sampling method. This study aimed to examine the importance of positional behavior flexibility in limestone forests characterized by seasonal variations in climate and food resources. Our results indicated that langurs adopted leaping (47.92% ± 5.50%) and vertical climbing (40.13% ± 6.20%) as their predominant locomotor modes and sitting (83.08% ± 4.70%) as their predominant posture. Their positional behavior exhibited marked seasonal variations. More specifically, langurs used quadrupedal walking more frequently during the dry season than during the rainy months. In the stationary state, they sat more frequently during the dry season, whereas they laid and suspended more often during the rainy season. Their positional behavior was affected by fruit availability, day length, and temperature. Quadrupedal walking increased with the decrease in fruit availability, whereas leaping was positively correlated with fruit availability. Moreover, sitting was positively correlated with average temperature but negatively correlated with day length. Lying was also negatively correlated with temperature but positively correlated with day length. We conclude that white‐headed langurs adapt to limestone forests with positional behavior flexibility in response to seasonality. Our research provides evidence of the effects of food availability, ambient temperature, and day length on the positional behavior of white‐headed langurs, highlighting the need to understand their behavioral ecology and the influence of ecological factors on behavioral adaptation. [ABSTRACT FROM AUTHOR]

The morphology of the cranial thoracic vertebrae has long been neglected in the study of primate skeletal functional morphology. This study explored the characteristics of the third to sixth thoracic vertebrae among various positional behavioural primates. A total of 67 skeletal samples from four species of hominoids, four of cercopithecoids, and two of platyrrhines were used. Computed tomography images of the thoracic vertebrae were converted to a three-dimensional (3D) bone surface, and 104 landmarks were obtained on the 3D surface. For size-independent shape analysis, the vertebrae were scaled to the same centroid size, and the normalised landmarks were registered using the generalised Procrustes method. Principle components of shape variation among samples were clarified using the variance–covariance matrix of the Procrustes residuals. The present study revealed that the transverse processes were more dorsally positioned in hominoids compared to non-hominoids. The results showed that not only a dorsolaterally oriented but also a dorsally positioned transverse process in relation to the vertebral arch contribute to the greater dorsal depth in hominoids than in monkeys. The thoracic vertebrae of Ateles and Nasalis show relatively dorsoventrally low and craniocaudally long vertebrae with craniocaudally long zygapophyses and craniocaudally long base/short tip of the caudally oriented spinous process, accompanied by a laterally oriented and craniocaudally long base of the transverse process. Despite being phylogenetically separated, the vertebral features of Ateles (suspensory platyrrhine with its prehensile tail's aid) are similar to those of Nasalis (arboreal quadrupedal/jumping/arm-swing colobine). The morphology of the third to sixth thoracic vertebrae tends to reflect the functional adaptation in relation to positional behaviour rather than the phylogenetic characteristics of hominoids, cercopithecoids, and platyrrhines. [ABSTRACT FROM AUTHOR]

Body size and individual development significantly affect positional behavior and substrate use. However, only a few studies have been conducted on immature wild macaques. We studied wild Tibetan macaques (Macaca thibetana) inhabiting Mt. Huangshan, China, to explore the degree of interspecific variation in positional behavior in relation to body weight and individual development. From September 2020 to August 2021, we used instantaneous scan sampling (duration 5 min, interval 10 min) to record age–sex groups, locomotions, postures, and substrate attributes. The results showed that Tibetan macaques used terrestrial substrates in nearly two-thirds of the recorded observations. The main postural modes were sitting and quadrupedal standing. The main locomotor modes were quadrupedal walking and climbing among all age–sex group records. Positional behavior and substrate use in adults only significantly differed from those in juveniles and infants. Although adult males were larger than the other age–sex groups, they did not climb and bridge more frequently than the other age–sex groups. The frequency of climbing, leaping, and suspension was significantly higher in juveniles than in adults. In addition, adult males used terrestrial and larger substrates more frequently, while juveniles and infants used arboreal substrates and terminals more frequently than adult males during traveling and feeding. We hypothesize that the more positional behavioral spectrum of Tibetan macaque juveniles’ may be related to rapid skeletal muscle development. These results suggest that differences in interspecific positional behavior may be caused by the individual development and survival needs of individuals, rather than just body size.

Positional behavior and its relationship with substrate are crucial to understand animal morphological and behavioral adaptation, and can contribute to habitat conservation of endangered species. Colobine monkeys show diverse inter- and intra-species variations in positional behavior. Although the effects of substrate type on positional behavior are well acknowledged, this relationship has rarely been investigated in the genus Trachypithecus. We studied positional behavior of Indo-Chinese gray langurs (Trachypithecus crepusculus) in a primary subtropical evergreen broad-leaved forest for 12 continuous months, and tested the effect of substrate type on their positional behavior. The study group mainly adopted sitting during resting and feeding, and primarily used quadrupedalism (including quadrupedal walking and running) and leaping for traveling, which is different from other species of Trachypithecus living in degraded limestone habitats. Substrate type affected the langurs’ locomotor mode. The langurs tended to leap more on twigs, climb more on lianas and quadrupedal move more on wide and solid substrates. Gap-crossing and security during traveling could explain this flexible locomotion pattern observed on different substrate types. Our results provide important insights into in-situ habitat conservation and ex-situ cage enrichment of langurs.

Immature mammals require opportunities to develop skills that will affect their competitive abilities and reproductive success as adults. One way these benefits may be achieved is through play behavior. While skills in developing use of tusks, antlers, and other weapons mammals have been linked to play, play in venomous animals has rarely been studied. Javan slow lorises (Nycticebus javanicus) use venom to aid in intraspecific competition, yet whether individuals use any behavioral mechanisms to develop the ability to use venom remains unclear. From April 2012 to December 2020, we recorded 663 play events and studied the factors influencing the frequency of play and the postures used during play in wild Javan slow lorises. Regardless of the presence of siblings, two thirds of play partners of young slow lorises were older and more experienced adults. Young lorises engaged in riskier behaviors during play, including using more strenuous postures and playing more in riskier conditions with increased rain and moonlight. We found that play patterns in immature lorises bear resemblance to venom postures used by adults. We suggest that play functions to train immature lorises to deal with future unexpected events, such as random attacks, as seen in other mammalian taxa with weapons. Given the importance of venom use for highly territorial slow lorises throughout their adult lives and the similarities between venom and play postures, we cannot rule out the possibility that play also prepares animals for future venomous fights. We provide here a baseline for the further exploration of the development of this unique behavior in one of the few venomous mammals.

Given that most species of primates are predominantly arboreal, maintaining the ability to move among branches of varying sizes has presumably been a common selective force in primate evolution. However, empirical evaluations of the relationships between morphological variation and characteristics of substrate geometry, such as substrate diameter relative to an animal's body mass, have been limited by the lack of quantified substrate usage in the wild. Here we use recently published quantitative data to assess the relationships between relative substrate size and talar morphology in nine New World monkey species at the Tiputini Biodiversity Station, Ecuador. Within this sample, both fibular facet angle (the angle between the fibular facet and the trochlear rims) and body-mass-standardized area of the medial tibial facet decrease as average and maximum relative substrate size increases. Correlations between medial tibial facet area and relative substrate size are driven by the inclusion of callitrichids in this sample. Nevertheless, these findings strengthen the hypothesis that variation in fibular facet orientation and medial tibial facet area are functionally correlated with habitual degrees of pedal inversion. They also strengthen the notion that evolutionarily changing body mass could impact habitat geometry experienced by a lineage and thereby substantially impact major trends in primate morphological evolution. This study highlights the importance of empirical data on substrate use in living primates for inferring functional and evolutionary implications of morphological variation. [ABSTRACT FROM AUTHOR]

Abstract Plesiadapiforms, like other Paleogene mammals, are known mostly from fossil teeth and jaw fragments. The several families of plesiadapiforms known from partial skeletons have all been reconstructed as arborealists, but differences in postcranial morphology among these taxa indicate a diversity of positional behaviors. Here we provide the first detailed descriptions and comparisons of a dentally associated partial skeleton (NMMNH P-54500) and of the most complete dentary with anterior teeth (NMMNH P-71598) pertaining to Torrejonia wilsoni , from the early Paleocene (late Torrejonian To3 interval zone) of the Nacimiento Formation, San Juan Basin, New Mexico, USA. NMMNH P-54500 is the oldest known partial skeleton of a plesiadapiform and the only known postcrania for the Palaechthonidae. This skeleton includes craniodental fragments with all permanent teeth fully erupted, and partial forelimbs and hind limbs with some epiphyses unfused, indicating that this individual was a nearly fully-grown subadult. Analysis of the forelimb suggests mobile shoulder and elbow joints, a habitually flexed forearm, and capacity for manual grasping. The hip joint allowed abduction and lateral rotation of the thigh and provides evidence for frequent orthograde postures on large diameter supports. Other aspects of the hind limb suggest a habitually flexed thigh and knee with no evidence for specialized leaping, and mobile ankle joints capable of high degrees of inversion and eversion. Although it is likely that some variability exists within the group, analysis of this skeleton suggests that palaechthonids are most like paromomyids among plesiadapiforms, but retain more plesiomorphic postcranial features than has been documented for the Paromomyidae. These observations are congruent with craniodental evidence supporting palaechthonids and paromomyids as closely related within the Paromomyoidea. The skeleton of T. wilsoni also demonstrates that many regions of the postcranium were already well adapted for arboreality within the first few million years of the diversification of placental mammals following the Cretaceous-Paleogene extinction event. [ABSTRACT FROM AUTHOR]

Over the last decade, we have learned much about the anatomy, evolutionary history, and biomechanics of the extant sloths. However, most of this study has involved studying sloths in controlled conditions, and few studies have explored how these animals are behaving in a naturalistic setting. In this study, we integrate positional activities in naturalistic conditions with kinematic and kinetic observations collected on a simulated runway to best capture the biomechanical behavior of Linnaeus's twotoed sloths. We confirm that the dominant positional behaviors consist of hanging below the support using a combination of forelimbs and hindlimbs, and walking quadrupedally below the branches. The majority of these behaviors occur on horizontal substrates that are approximately 5-10 cm in diameter. The kinematics of suspensory walking observed both in the naturalistic settings and on simulated arboreal runways are dominated by movement of the proximal limb elements, while distal limb elements tend to show little excursion. Joint kinematics are similar between the naturalistic setting and the simulated runway, but movements of the shoulder and hip tend to be exaggerated while moving in simulated conditions. Kinetic patterns of the two-toed sloth can be explained almost entirely by considering them as an inverted linked strut. However, medially directed forces toward the substrate were more frequent than expected in the forelimb, which may help sloths maintain a better "grip" on the substrate. This study serves as a model of how to gain a comprehensive understanding of the functional-adaptive profile of a particular species. [ABSTRACT FROM AUTHOR]

Locomotor diversity has meant many different things depending on the subject area or investigator. While no concrete definition of locomotor diversity is currently available, this has not stopped researchers from making a number of assertions about the underlying mechanisms that determine whether a species will have high or low locomotor diversity. Some of these claims include that: (1) arboreal primates demonstrate higher locomotor diversity than terrestrial species; (2) anatomically generalized and small‐bodied primates demonstrate higher locomotor diversity than anatomically specialized and large‐bodied taxa; and (3) primates demonstrate higher locomotor diversity compared to non‐primate mammals. None of these claims have been tested in any sort of comparative framework. Using previously published locomotor repertoire data from 110 mammalian species, this study co‐opted the Shannon–Wiener diversity index to calculate a singular measure of locomotor diversity. Phylogenetic analyses of these locomotor diversity indices reveal that within primates, small‐bodied species demonstrate greater locomotor diversity than large‐bodied taxa. However, this effect becomes non‐significant when accounting for differences in substrate‐use (i.e. arboreal vs. terrestrial). Anatomical specialization has no effect on locomotor diversity in primates. Furthermore, primates do not inherently have greater locomotor diversity than other mammalian taxa. Findings from this study suggest that movement on arboreal substrates requires all mammals, regardless of taxonomic affiliation, to demonstrate high locomotor diversity. These data further highlight the challenges faced by arboreal animals and raise the possibility that being able to switch fluidly and frequently between many different locomotor modes may be advantageous for animals moving in an arboreal milieu. Locomotor diversity has meant many different things depending on the subject area or investigator, but there is no concrete definition of locomotor diversity currently available. Using previously published locomotor repertoire data from 110 mammalian species, this study co‐opted the Shannon–Wiener diversity index to calculate a singular measure of locomotor diversity. Phylogenetic analyses of these locomotor diversity indices reveal that within primates, small‐bodied species demonstrate greater locomotor diversity than large‐bodied taxa. Furthermore, primates do not inherently have greater locomotor diversity than other mammalian taxa. Findings from this study suggest that movement on arboreal substrates requires all mammals, regardless of taxonomic affiliation, to demonstrate high locomotor diversity. These data further highlight the challenges faced by arboreal animals and raise the possibility that being able to switch fluidly and frequently between many different locomotor modes may be advantageous for animals moving in an arboreal milieu. [ABSTRACT FROM AUTHOR]

This study reported the body mass (BM) estimates of the Middle Miocene fossil hominoid Nacholapithecus kerioi from Africa. The average BM estimates from all forelimb and hindlimb skeletal elements was 22.7 kg, which is slightly higher than the previously reported estimate of ~22 kg. This study revealed that Nacholapithecus has a unique body proportion with an enlarged forelimb relative to a smaller hindlimb, suggesting an antipronograde posture/locomotion, which may be related to the long clavicle, robust ribs, and some hominoid-like vertebral morphology. Because the BM of Nacholapithecus in this study was estimated to be below 30 kg, Nacholapithecus probably did not have relatively shorter and robust femora, which may result from other mechanical constraints, as seen in extant African hominoids. The BM estimate of Nacholapithecus suggests that full substantial modifications of the trunk and forelimb anatomy for risk avoidance and foraging efficiency, as seen in extant great apes, would not be expected in Nacholapithecus. Because larger monkeys are less arboreal (e.g., Mandrillus sphinx or Papio spp.), and the maximum BM among extant constant arboreal cercopithecoids is ~24 kg (male Nasalis larvatus), Nacholapithecus would be a constant arboreal primate. Although caution should be applied because of targeting only males in this study, arboreal quadrupedalism with upright posture and occasional antipronograde locomotion (e.g., climbing, chambering, descending, arm-swing, and sway) using the powerful grasping capacity of the hand and foot may be assumed for positional behavior of Nacholapithecus., (© 2023 American Association for Anatomy.)

Positional behavior (posture and locomotion) studies are a category of primatological and anthropological field research that attempts to describe movement capabilities and expressed behavior within an evolutionary, ecological, and/or morphological context. This area of research is appealing because it allows the integration of morphological data (capabilities) with expressed behaviors and provides a basis for understanding fossil reconstruction. Because positional behavior acts as a mediator between the biology and the environment, it offers information about virtually all aspects of a primate's life. We are currently undergoing an increase in the number of field projects focusing on the development of positional behaviors in immature primates, and results suggest that in many species positional competence develops relatively early. In this review, I present information on recent positional behavior studies with a focus on how positional behavior develops in young primates. Research on immature primates suggests that natural selection operates at all life stages to influence survival and that the adult positional repertoire likely reflects the challenges confronted by younger individuals. [ABSTRACT FROM AUTHOR]

Although resting is one of the dominant behaviors of foregut-fermenting primates (i.e., colobines), their resting posture has rarely received attention. We hypothesize that colobines are more constrained in their resting position than hindgut-fermenting primates and that colobines assume a sitting resting position for specific reasons. To test this hypothesis, we followed two approaches. First, we observed resting positions in two captive individuals each of eight species and tested whether colobines rested in a sitting position more than other primates. Second, we collected literature data on free-ranging specimens of 31 species and again tested whether colobines rested in a sitting position more than other primates. Both approaches indicated that colobines spent more time in a sitting posture than other primates (73.0% vs. 23.2% in captivity and 83.0% vs. 60.9% in the wild, respectively). We hypothesize that the position of the digestive chamber and the necessity of frequently having to eructate digestion gases force colobines to take a sitting posture to avoid pressure on the thorax and respiratory organs. [ABSTRACT FROM AUTHOR]

Locomotion and postures are key factors to understanding the biology of animals. However, scansorial and arboreal carnivorans remain poorly studied regarding these issues. Herein, we present a behavioral and morphological analysis of the arboreal locomotion of the tayra ( Eira barbara ), a neotropical forest-dwelling mustelid. Data on habitat use and locomotor and postural modes were collected from free-ranging tayras in a terra-firme forest in French Guiana. Additionally, qualitative morphological traits and linear measurements of the girdles and appendicular skeleton were analyzed through comparative anatomical descriptions, univariate tests, and a principal components and discriminant analysis. Tayras frequently used clambering, quadrupedal walking, claw climbing and quadrupedal standing, performed primarily on small and medium, oblique and horizontal branches. Furthermore, our morpho-functional analyses revealed that tayras possess autopodial specializations for navigating on arboreal substrates, while the more proximal elements present features more similar to other terrestrial or scansorial mustelids, and theoretically less modified from the hypothetical weasel-like ancestor of mustelids. This mosaic of morphological features of the tayra, a combination of phylogenetic inertia and ecological signals, very likely evolved to promote the efficient and effective exploitation of diverse habitats and resources in this versatile species. [ABSTRACT FROM AUTHOR]

We carried out a multidisciplinary study linking behavioral and morphological data from a little-known guenon species, Cercopithecus solatus, endemic to Gabon. Over a period of 9 months, we documented the pattern of stratum use associated with postural and locomotor behavior by direct observation (650 hrs) of a semi-free-ranging breeding colony. We also conducted a morphometric analysis of the humerus and limb proportions of 90 adult specimens from 16 guenon species, including C. solatus. Field observations indicated that C. solatus monkeys spent a third of their time on the ground, similar to semi-terrestrial guenon species. We detected two patterns of stratum use: at ground level, and in trees, at a height of 3-10 m. The monkeys spent more time on the ground during the dry season than the wet season, feeding mainly at ground level, while resting, and social behaviors occurred more frequently in the tree strata. Our study of humerus size and shape, together with the analysis of limb proportions, indicated morphofunctional adaptation of C. solatus to greater terrestriality than previously thought. We therefore characterize C. solatus as a semi-terrestrial guenon, and propose a new hypothesis for the ancestral condition. By combining behavioral and morphological results, we provide new information about the adaptive strategies of the species, and the evolutionary history of guenons, thus contributing to the conservation of the sun-tailed monkey in the wild. Am. J. Primatol. 77:1060-1074, 2015. © 2015 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

In order to exploit the three-dimensional, discontinuous and unstable arboreal milieu, most arboreal mammals employ efficient foot (pedal) grasping that establishes firm contact with the substrate and enables secure and safe locomotion and postures. Such pedal grasp can be performed in variable ways in relation to substrate characteristics. In order to investigate the interplay between pedal grasping modes, arboreal locomotor and postural behavior, and substrate size and inclination in arboreal mammals, we filmed and quantitatively analyzed these behaviors in captive African woodland dormice. Our observations revealed that African woodland dormice exhibited a flexible locomotor and postural repertoire, mainly on small and horizontal substrates. Hallucal grasping was the main pedal grasping mode and associated with walk, clamber and stand on mainly small- to medium-sized horizontal substrates, whereas claws were commonly used during vertical climb and cling on medium-sized to large vertical substrates. These results clearly demonstrate the importance of hallucal grasping for balancing above, and not below, small- and medium-sized arboreal substrates of moderate inclinations. Therefore, we assert that efficient pedal grasping and its associated positional behavior may have been fundamental for the differentiation and successful radiation of virtually all early mammals that sought refuge in tree canopies, enabling efficient utilization of the small branch niche. Evidence suggests that extant arboreal rodents offer useful functional morphology evidence of the transitional stages that lead to arboreal specialists, euprimates included, and research toward this direction has much to offer to our understanding of evolutionary adaptations exhibited by small-bodied arboreal mammals. [ABSTRACT FROM AUTHOR]

ABSTRACT The nightly construction of arboreal sleeping platforms or 'nests' has been observed among every great ape population studied to date. However, this behavior has never been reported in any other nonhuman primate and comparisons between ape and monkey sleep illuminate the link between sleeping substrates, positional behavior, and sleep efficiency. Here, we compare sleep depth and efficiency and night-time positional behavior between a large-bodied cercopithecoid ( Papio papio) and a large-bodied hominoid ( Pongo spp.) at the Indianapolis Zoo. We used infrared videography to assess nightly sleep and awake behavioral states, gross body movements, and postures in baboons ( N = 45 nights) and orangutans ( N = 128 nights). We calculated the total waking time, total sleep time, sleep fragmentation (the number of brief awakenings ≥2 min/h), sleep motor activity (number of motor activity bouts per hour), sleep efficiency (sleep duration/time in bed), and percentage of time spent in each posture. By every measure, orangutans experienced overall deeper, more efficient sleep. Baboons were more likely to sleep in guarded, upright positions (weight bearing on their ischial callosities) and never opted to use additional materials to augment sleep environments, whereas orangutans slept in insouciant, relaxed positions on constructed sleeping materials. Our results suggest that relaxed sleeping postures may have been enabled by sleeping platforms as a behavioral facilitator to sleep, which could have allowed for greater sleep depth and next-day cognitive capacities in both great apes and hominins. Am J Phys Anthropol 157:421-427, 2015. © 2015 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

ABSTRACT The vertebral column plays a key role in maintaining posture, locomotion, and transmitting loads between body components. Cervical vertebrae act as a bridge between the torso and head and play a crucial role in the maintenance of head position and the visual field. Despite its importance in positional behaviors, the functional morphology of the cervical region remains poorly understood, particularly in comparison to the thoracic and lumbar sections of the spinal column. This study tests whether morphological variation in the primate cervical vertebrae correlates with differences in postural behavior. Phylogenetic generalized least-squares analyses were performed on a taxonomically broad sample of 26 extant primate taxa to test the link between vertebral morphology and posture. Kinematic data on primate head and neck postures were used instead of behavioral categories in an effort to provide a more direct analysis of our functional hypothesis. Results provide evidence for a function-form link between cervical vertebral shape and postural behaviors. Specifically, taxa with more pronograde heads and necks and less kyphotic orbits exhibit cervical vertebrae with longer spinous processes, indicating increased mechanical advantage for deep nuchal musculature, and craniocaudally longer vertebral bodies and more coronally oriented zygapophyseal articular facets, suggesting an emphasis on curve formation and maintenance within the cervical lordosis, coupled with a greater resistance to translation and ventral displacement. These results not only document support for functional relationships in cervical vertebrae features across a wide range of primate taxa, but highlight the utility of quantitative behavioral data in functional investigations. Am J Phys Anthropol 156:531-542, 2015. © 2015 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

ABSTRACT Identification of positional behavior adaptation in the pelvis of primates is complicated by possible confounding effects of body size and phylogeny. Previous work on primate pelvic allometry has focused primarily on sexual dimorphism and its relationship to obstetric constraints in species with large fetal size relative to maternal size. This study investigates patterns of pelvic scaling with a specific aim to understand how pelvic scaling relates to locomotor function. Patterns of scaling of nine pelvic dimensions were examined in a broad comparative sample of 40 species of primates, covering both haplorhines and strepsirrhines, while accounting for phylogenetic nonindependence. Phylogenetic reduced major axis regressions on pelvic scaling patterns suggest that primate-wide patterns are reflected in haplorhine- and strepsirrhine-specific analyses. Many measures scale isometrically with pelvis size, but notably, features of the ilium tend to scale allometrically. As predicted, ilium width and lower ilium cross-sectional area scale with positive allometry, while lower iliac height scales with negative allometry. Further regression analyses by locomotor group suggest that these ilium measures, as well as pubic symphysis and ischium lengths, differ in their scaling patterns according to locomotor mode. These results suggest that scaling differences within primates, when present, are related to functional differences in locomotor behavior and mechanics. This study supports recent work that identifies adaptations to locomotor loading in the ilium and highlights the need for a better understanding of the relationship between pelvic structural mechanics and the mechanical requirements of primate locomotion. Am J Phys Anthropol 156:511-530, 2015. © 2015 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Information on the positional behavior and habitat use of primates can help elucidate relationships among species' morphology, behavior, and environment, and contribute to our understanding of species' behavioral and ecological adaptations. Limestone habitats provide a unique and challenging habitat for primates, but there have been few detailed studies of the genus Macaca in such habitats, making a comparative understanding of extant limestone primates' behavioral adaptations incomplete. We collected data on positional behavior and habitat use by sympatric Assamese macaques ( Macaca assamensis) and rhesus macaques ( M. mulatta) in limestone habitat at Nonggang Nature Reserve, southwestern Guangxi, China, and examined the effects of morphological and ecological factors on positional behavior and habitat use. Our results indicate interspecific differences in positional behavior, showing different preferences for locomotor modes and substrates. Rhesus macaques tended to walk horizontally, whereas Assamese macaques more often climbed vertically. Rhesus macaques used smaller substrates (twigs) more frequently than did Assamese macaques. Time spent in different zones of limestone hills and forest strata also varied significantly between the two macaques. Assamese macaques most often used cliff faces, and tended to be terrestrial. Rhesus macaques were most likely to stay low on the hillsides, and spent most of their time in the lower strata of trees. These differences in positional behavior and habitat use are linked to differences in limb length and body size in the two species, and may be explained by the spatial distribution of preferred foods and structure of the forest in different areas of the limestone hills. [ABSTRACT FROM AUTHOR]

We describe a partial innominate, YGSP 41216, from a 12.3 Ma locality in the Siwalik Group of the Potwar Plateau in Pakistan, assigned to the Middle Miocene ape species Sivapithecus indicus. We investigate the implications of its morphology for reconstructing positional behavior of this ape. Postcranial anatomy of extant catarrhines falls into two distinct groups, particularly for torso shape. To an extent this reflects different although variable and overlapping positional repertoires: pronograde quadrupedalism for cercopithecoids and orthogrady for hominoids. The YGSP innominate (hipbone) is from a primate with a narrow torso, resembling most extant monkeys and differing from the broader torsos of extant apes. Other postcranial material of S. indicus and its younger and similar congener Sivapithecus sivalensis also supports reconstruction of a hominoid with a positional repertoire more similar to the pronograde quadrupedal patterns of most monkeys than to the orthograde patterns of apes. However, Sivapithecus postcranial morphology differs in many details from any extant species. We reconstruct a slow-moving, deliberate, arboreal animal, primarily traveling above supports but also frequently engaging in antipronograde behaviors. There are no obvious synapomorphic postcranial features shared exclusively with any extant crown hominid, including Pongo. [ABSTRACT FROM AUTHOR]