Positional behavior ofCebuella pygmaea in Yasuni National Park, Ecuador

In terms of positional behavior, the small-bodied callitrichids are distinguished from other anthropoids by their ability to leap between and to cling to large vertical supports, feeding occasionally or frequently on sap and bark insects. In this paper, I studied the positional behavior of a group of pygmy marmosets in a hilly wet tropical forest in Yasuni National Park, Ecuador. During traveling, the animals used quadrupedal walk/bound and leaping mostly on small horizontal supports. During foraging, quadrupedal walk/bound and clambering dominated. The main foraging postures were stand and cantilever, occurring mainly on small horizontal lianas. During feeding, scansorial locomotion was used very frequently. Claw clinging was the dominant feeding posture. Furthermore, large vertical lianas and tree boles were the most frequent feeding supports. These observations would suggest that scansorial locomotion, vertical clinging, and vertical leaping are most likelynot part of the same form function complex. Vertical leaps appear to be associated with moving in the lower parts of the forest. On the other hand, scansorial locomotion and vertical clinging appear to be related to feeding on the sap of tree boles and large lianas in the lower parts of the forest.     

Positional behavior of Siberian chipmunks (Tamias sibiricus) in captivity

Arboreal and semi-arboreal mammals have remarkably diverse positional behavior and associated morpho-functional adaptations related to the three-dimensional nature of their arboreal habitat. In this context, we investigated the positional behavior of captive Siberian chipmunks (Tamias sibiricus), small bodied semi-arboreal sciurids, in an aviary-type wire-mesh cage containing both terrestrial and arboreal supports. We sampled four adult individuals during a five-month period using focal animal sampling every 30 s. Results showed that animals preferred 8–10 cm horizontal supports and always avoided vertical supports. Locomotion occurred on both terrestrial and 8–10 cm arboreal supports whereas postural behavior occurred primarily on 8–10 cm arboreal supports. Quadrupedal walk dominated during locomotion, and occurred primarily on terrestrial horizontal supports, as is observed for other squirrels. The predominance of quadrupedal locomotion is consistent with the postcranial morphology of chipmunks. In contrast, clawed locomotion occurred on wire mesh and on >13 cm arboreal vertical supports. Finally, pronograde and orthograde sitting, both on 8–10 cm arboreal supports and on terrestrial supports, were the predominant postures, implying general predisposition to selection of stable postures on stable supports for food item manipulation and ingestion.     

Positional behavior of the white uakari (Cacajao calvus calvus)

The positional behavior and habitat use of a group of white uakaries (Cacajao calvus calvus) was observed for 6 weeks in the dry season at Lake Teiú, Brazil. Data are presented for feeding, traveling, and resting activities. The most common feeding posture is sit, followed by stand. Cacajao frequently exhibits locomotor behaviors while in feeding trees, using pronograde clamber and quadrupedal walk. The most frequently used locomotor behaviors in travel are quadrupedal walk, leap, and pronograde clamber. Quadrupedal run and drop also figure importantly in the behavioral repertoire. The most frequent resting posture was sit, followed by ventral lie. Compared to representative members of the other pitheciin genera, Pithecia and Chiropotes, Cacajao engages in more locomotion while feeding, and uses more pedal suspension. While traveling, pronograde clamber and drop are more frequently used by Cacajao. Multiple, deformable supports are used more by Cacajao than by the other pitheciins throughout all activities. Overall, the positional behavior of Cacajao is more similar to that of Chiropotes than of Pithecia. Cacajao's behavioral solutions to the problems of balance imposed by its greatly reduced tail are discussed. © 1996 Wiley-Liss, Inc.     

Locomotor adaptations reflected in the wrist joints of early tertiary primates (adapiformes)

The positional behaviors inferred for early Tertiary adapiform primates have been the subject of considerable debate. Adapiform wrist morphology is analyzed here within the context of extant morphoclines in carpal joint shape in order to reconstruct adapiform positional behavior. Extant vertical clingers, slow climbers, and arboreal quadrupeds differ significantly from one another in length of the m. flexor carpi ulnaris lever arm, shape of the midcarpal joint articular surface, and size and divergence of the pollical carpometacarpal articulation. These morphological differences are functionally related to differential requirements for wrist flexion, midcarpal mobility and stability, and pollical grasping, respectively. Adapis, Notharctus, and Smilodectes share with living arboreal quadrupeds a tall pisiform body, a mediolaterally flat midcarpal joint surface, and a relatively unexpanded thumb joint. Functionally, these features are related to flexing the wrist from extended positions during palmigrade, quadrupedal locomotion, increasing midcarpal joint stability during quadrupedal, weight-bearing postures, and grasping arboreal supports of predominantly horizontal and oblique orientation. The Messel adapiform (genus indet.) shares certain features of the midcarpal and pollical carpometacarpal articulations with extant vertical clingers, suggesting that this taxon used vertical substrates more frequently than other adapiforms. © 1996 Wiley-Liss, Inc.     

Locomotor behavior of wild orangutans (Pongo pygmaeus wurmbii) in disturbed peat swamp forest, Sabangau, Central Kalimantan, Indonesia

This study examined the locomotor behavior of wild Bornean orangutans (P. p. wurmbii) in an area of disturbed peat swamp forest (Sabangau Catchment, Indonesia) in relation to the height in the canopy, age-sex class, behavior (feeding or traveling), and the number of supports used to bear body mass. Backward elimination log-linear modeling was employed to expose the main influences on orangutan locomotion. Our results showed that the most important distinctions with regard to locomotion were between suspensory and compressive, or, orthograde (vertical trunk) and pronograde (horizontal trunk) behavior. Whether orangutans were traveling or feeding had the most important influence on locomotion whereby compressive locomotion had a strong association with feeding, suspensory locomotion had a strong association with travel in the peripheral strata using multiple supports, whereas vertical climb/descent and oscillation showed a strong association with travel on single supports in the core stratum. In contrast to theoretical predictions on positional behavior and body size, age-sex category had a limited influence on locomotion. The study revealed that torso orthograde suspension dominates orangutan locomotion, concurring with previous studies in dipterocarp forest. But, orangutans in the Sabangau exhibited substantially higher frequencies of oscillatory locomotion than observed at other sites, suggesting this behavior confers particular benefits for traversing the highly compliant arboreal environment typical of disturbed peat swamp forest. In addition, torso pronograde suspensory locomotion was observed at much lower levels than in the Sumatran species. Together these results highlight the necessity for further examination of differences between species, which control for habitat.     

Sex differences in adult chimpanzee positional behavior: The influence of body size on locomotion and posture

Focal animal instantaneous sampling of adult male and female chimpanzee positional behavior was conducted during a 7-month study in the Tai Forest, Ivory Coast, in order to determine whether there are sex differences in the locomotion, posture, substrate use, and height preference of sexually dimorphic adult chimpanzees, and if so, whether these differences support predictions based on body size differences. Results indicate that as predicted, adult male and female chimpanzees differ in their arboreal locomotor behavior, with the larger males using less quadrupedalism and more climbing, scrambling, and aided bipedalism than females during feeding locomotion. There is a sex difference in height preference as well, with female chimpanzees consistently using more arboreal behavior than males, primarily during resting. Although it has been previously demonstrated that separate primate species of differing body size differ in locomotor and postural activities (Fleagle and Mittermeier, 1980; Crompton, 1984), this study clearly demonstrates that body size differences within a species can also be correlated with differences in locomotor behavior. These findings may influence how we interpret sex differences in body size of extinct species. © 1993 Wiley-Liss, Inc.     

Functional morphology of the lemuriform wrist joints and the relationship between wrist morphology and positional behavior in arboreal primates

A comparative study of carpal joint structure and function in six Malagasy lemuriforms was undertaken to test predicted morphoclines in carpal joint morphology between pronograde and orthograde arboreal primates. Patterns of movement at the wrist during locomotion were observed and described for the lemuriform species Lemur fulvus and Propithecus verreauxi. Lemur fulvus, which assumes a pronograde posture during locomotion, extends and pronates the wrist during the support phase of quadrupedal walking and running stride cycles. Furthermore, the forearm of this species exhibits some transverse movement across the proximal wrist joint during the support phase. In contrast, the indriid Propithecus maintains the hand and wrist in a flexed and partially supinated position during vertical clinging and suspensory postures. Habitual quadrupedal and vertical postures in Malagasy primates are in turn related to very different patterns of carpal joint morphology and articular mechanics. Those lemurs which are predominantly pronograde share a series of structural features related to stabilizing the antebrachiocarpal joint during extension and mediolateral deviation and the midcarpal joint during pronation: an intraarticular labrum is present on the inner portion of the radiocarpal ligament, the radiocarpal articular surface is quite flat dorsoventrally, the capitate-trapezoid embrasure is expanded dorsally, and development of the radial and ulnar styloids is more pronounced. The wrists of Propithecus, Avahi, and Lepilemur (vertical clingers) differ from those of quadrupedal lemuriforms in possessing a suite of morphological features related to stabilizing the wrist during antebrachiocarpal flexion and midcarpal supination: the radiocarpal articular surface is deeply curved and tilted anteriorly, the dorsal radiocarpal ligament is very broad, thick, and fibrous, the hamate's triquetral facet is directed proximodistally, and the capitate-trapezoid embrasure is dorsally constricted and expanded palmarly. These observed contrasts in carpal form and function are used to define further the morphological features related to orthograde posture in several lineages of arboreal primates. © 1996 Wiley-Liss, Inc.     

Climbing,brachiation, and terrestrial quadrupedalism: Historical precursors of hominid bipedalism

The vertical-climbing account of the evolution of locomotor behavior and morphology in hominid ancestry is reexamined in light of recent behavioral, anatomical, and paleontological findings and a more firmly established phylogeny for the living apes. The behavioral record shows that African apes, when arboreal, are good vertical climbers, and that locomotion during traveling best separates the living apes into brachiators (gibbons), scrambling/climbing/brachiators (orangutans), and terrestrial quadrupeds (gorillas and chimpanzees). The paleontological record documents frequent climbing as an ancestral catarrhine ability, while a reassessment of the morphology of the torso and forelimb in living apes and Atelini suggests that their shared unique morphological pattern is best explained by brachiation and forelimb suspensory positional behavior. Further, evidence from the hand and foot points to a terrestrial quadrupedal phase in hominoid evolution prior to the adoption of bipedalism. The evolution of positional behavior from early hominoids to hominids appears to have begun with an arboreal quadrupedal-climbing phase and proceeded though an orthograde, brachiating, forelimb-suspensory phase, which was in turn followed by arboreal and terrestrial quadrupedal phases prior to the advent of hominid bipedality. The thesis that protohominids climbed down from the trees to become terrestrial bipeds needs to be reexamined in light of a potentially long history of terrestriality in the ancestral protohominid. © 1996 Wiley-Liss, Inc.     

Functional aspects of strepsirrhine lumbar vertebral bodies and spinous processes

The relationship between form and function in the lumbar vertebral column has been well documented among platyrrhines and especially catarrhines, while functional studies of postcranial morphology among strepsirrhines have concentrated predominantly on the limbs. This morphometric study investigates biomechanically relevant attributes of the lumbar vertebral morphology of 20 species of extant strepsirrhines. With this extensive sample, our goal is to address the influence of positional behavior on lumbar vertebral form while also assessing the effects of body size and phylogenetic history. The results reveal distinctions in lumbar vertebral morphology among strepsirrhines in functional association with their habitual postures and primary locomotor behaviors. In general, strepsirrhines that emphasize pronograde posture and quadrupedal locomotion combined with leaping (from a pronograde position) have the relatively longest lumbar regions and lumbar vertebral bodies, features promoting sagittal spinal flexibility. Indrids and galagonids that rely primarily on vertical clinging and leaping with orthograde posture share a relatively short (i.e., stable and resistant to bending) lumbar region, although the length of individual lumbar vertebral bodies varies phylogenetically and possibly allometrically. The other two vertical clingers and leapers, Hapalemur and Lepilemur, more closely resemble the pronograde, quadrupedal taxa. The specialized, suspensory lorids have relatively short lumbar regions as well, but the lengths of their lumbar regions are influenced by body size, and Arctocebus has dramatically longer vertebral bodies than do the other lorids. Lumbar morphology among galagonids appears to reflect a strong phylogenetic signal superimposed on a functional one. In general, relative length of the spinous processes follows a positively allometric trend, although lorids (especially the larger-bodied forms) have relatively short spinous processes for their body size, in accordance with their positional repertoire. The results of the study broaden our understanding of postcranial adaptation in primates, while providing an extensive comparative database for interpreting vertebral morphology in fossil primates.     

Primates in perspective. Review of “Order Primates,” pp. 352–450 in Walker's Mammals of the World, 4th Edition,by Ronald M. Nowak and John L. Paradiso. Baltimore and London,The Johns Hopkins University Press, 1983, 1362 pp., two-volume set, $65

This study examines the positional and activity behavior of a captive slow loris, Nycticebus coucang. The male individual was housed in a primate facility providing a seminatural environment and was subjected to a series of videotape recordings from which 1,878 point observations were taken. The enclosure was designed to allow maximum flexibility of substrate use. Quantitative information detailing activity, positional mode, and substrate geometry was collected using a checklist of 15 variables. Data were tabulated and compared as frequency distributions to describe activity budgets, the use of locomotor and postural modes, and the relation of posture to activity behavior and substrate geometry. The results indicated that almost 90% of the active day may be devoted to behaviors directly or indirectly related to dietary functions. For locomotor behavior, both climbing and walking were associated with the use of diagonal couplets. The loris devoted 52% of its positional behavior to postural modes, favoring the quadrupedal stand, triplets, and sitting. Suspension was found to be used more often in posture than locomotion. Overall, the loris's repertory of positional modes accommodated a wide range of substrate geometries.     

Locomotion and postures of red howlers in a deciduous forest-savanna interface

Positional (postural and locomotor) patterns and substrates used by the seven adults of a free-ranging troop of red howling monkeys (Alouatta seniculus) were identified and sampled during their feeding and resting. Traveling patterns and substrates were noted but not quantified. Arboreal locomotor behaviors were pronograde quadrupedalism, some leaping, bridging, lowering, and pull up. Sitting and reclining were the most frequent postures. Tail suspension and arboreal bipedal stance were used when feeding. Predominant locomotor behaviors were those in which limbs appeared to be compression stressed. There were no limb suspensions. The monkeys used the entire tree canopy, that of the low shrubs, and did a good deal of travel on the ground. The lack of forelimb suspension is attributed to the inability of these howlers to hang beneath supports and look forward at the same time; the impediment is created by the size of the vocal organs in the neck. The locomotion of these monkeys is offered to depict that of Aegyptopithecus zeuxis.     

Seasonal variation in the positional behavior of red howling monkeys (Alouatta seniculus)

Recent studies on the positional behavior of primates reveal that significant seasonal variation occurs in both locomotion and postures that is related to changes in diet and foraging techniques. Howling monkeys (genusAlouatta), which also have a seasonally varied diet, are predicted to have correspondingly varied positional behaviors. Two groups of red howling monkeys were studied in a primary rain forest in French Guinana during the dry and wet seasons. During the dry season, when howler diet is based mainly on leaves, howlers traveled more frequently by quadrupedal walking on large supports, a mode of progression that is probably inexpensive energetically and relatively stable. During feeding, quadrupedal and tripedal stand contributed considerably, a posture probably associated with the equal distribution of leaves within a tree crown. In contrast, during the wet season, when fruit was abundant, howlers fed very frequently by sitting on large supports, probably because fruit consumption required more time for special manipulation. However, most seasonal changes in feeding postures, and in travel and feeding locomotion, were difficult to associate directly with dietary shifts. These behavioral changes may be more highly correlated with slight modifications in microhabitat use (horizontal and vertical daily ranges, similar and alternative arboreal pathways) that are not considered in this paper.     

Interpreting the Role of Climbing in Primate Locomotor Evolution: Are the Biomechanics of Climbing Influenced by Habitual Substrate Use and Anatomy?

Vertical climbing is widely accepted to have played an important role in the origins of both primate locomotion and of human bipedalism. Yet, only a few researchers have compared climbing mechanics in quadrupedal primates that vary in their degree of arboreality. It is assumed that primates using vertical climbing with a relatively high frequency will have morphological and behavioral specializations that facilitate efficient climbing mechanics. We test this assumption by examining whether time spent habitually engaged in climbing influences locomotor parameters such as footfall sequence, peak forces, and joint excursions during vertical climbing. Previous studies have shown that during climbing, the pronograde and semiterrestrial Macaca fuscata differs in these parameters compared to the more arboreal and highly specialized, antipronograde Ateles geoffroyi. Here, we examine whether a fully arboreal, quadrupedal primate that does not regularly arm-swing will exhibit gait and force distribution patterns intermediate between those of Macaca fuscata and Ateles geoffroyi. We collected footfall sequence, limb peak vertical forces, and 3D hindlimb excursion data for Macaca fascicularis during climbing on a stationary pole instrumented with a force transducer. Results show that footfall sequences are similar between macaque species, whereas peak force distributions and hindlimb excursions for Macaca fascicularis are intermediate between values reported for M. fuscata and Ateles geoffroyi. These results support the notion that time spent climbing is reflected in climbing mechanics, even though morphology may not provide for efficient mechanics, and highlight the important role of arboreal locomotor activity in determining the pathways of primate locomotor evolution.     

Positional behavior of free-ranging Japanese macaques (<Emphasis Type="Italic">Macaca fuscata</Emphasis>)

Positional behavior was quantitatively studied in identified free-ranging Japanese macaques (Macaca fuscata). Five male and 11 female adults were observed in a forested mountain habitat. Data were analyzed for proportion of bout distance, number and time of each locomotion and postural type. Japanese macaques are semiterrestrial, and mainly walk and run quadrupedally. This supports the notion that Macaca are generally quadrupeds. Sex differences in positional behavior were found in the preference of substrate and types of positional behavior. Males and females tend to be terrestrial and arboreal, respectively. Males leap more frequently and longer in distance than do females when they are feeding in trees. These sex differences are considered to be related to differences in morphology, food choice, social activity, and the nursing of infants. Frequencies of leaping and the distance covered by leaping in Japanese macaques are more than those of long-tailed macaques which are arboreal quadrupeds. However, Japanese macaques leap shorter distances at a time than do long-tailed macaques, which indicates that body size may be related to leaping distance more than the frequency of leaping and the distance covered by leaping. Japanese macaques are not as specialized for terrestrial locomotion as pig-tailed macaques. They use both terrestrial and arboreal supports, and are considered to be semi-terrestrial quadrupeds, somewhere between the arboreal long-tailed macaque and the terrestrial pig-tailed macaque. Electronic Publication     

Arboreal bipedalism in wild chimpanzees: implications for the evolution of hominid posture and locomotion

Field observations of bipedal posture and locomotion in wild chimpanzees (Pan troglodytes) can serve as key evidence for reconstructing the likely origins of bipedalism in the last prehominid human ancestor. This paper reports on a sample of bipedal bouts, recorded ad libitum, in wild chimpanzees in Bwindi Impenetrable National Park in southwestern Uganda. The Ruhija community of chimpanzees in Bwindi displays a high rate of bipedal posture. In 246.7 hr of observation from 2001-2003, 179 instances of bipedal posture lasting 5 sec or longer were recorded, for a rate of 0.73 bouts per observation hour. Bipedalism was observed only on arboreal substrates, and was almost all postural, and not locomotor. Bipedalism was part of a complex series of positional behaviors related to feeding, which included two-legged standing, one-legged standing with arm support, and other intermediate postures. Ninety-six percent of bipedal bouts occurred in a foraging context, always as a chimpanzee reached to pluck fruit from tree limbs. Bipedalism was seen in both male and female adults, less frequently among juveniles, and rarely in infants. Both the frequency and duration of bipedal bouts showed a significant positive correlation with estimated substrate diameter. Neither fruit size nor nearest-neighbor association patterns were significantly correlated with the occurrence of bipedalism. Bipedalism is seen frequently in the Bwindi chimpanzee community, in part because of the unusual observer conditions at Bwindi. Most observations of bipedalism were made when the animals were in treetops and the observer at eye-level across narrow ravines. This suggests that wild chimpanzees may engage in bipedal behavior more often than is generally appreciated. Models of the likely evolutionary origins of bipedalism are considered in the light of Bwindi bipedalism data. Bipedalism among Bwindi chimpanzees suggests the origin of bipedal posture in hominids to be related to foraging advantages in fruit trees. It suggests important arboreal advantages in upright posture. The origin of postural bipedalism may have preceded and been causally disconnected from locomotor bipedalism.     

Locomotion in captive Leontopithecus and Callimico: A multimedia study

Video studies, gait analysis, footprint tracks, and observational scan sampling show that, in comparably furnished enclosures, Leontopithecus rosalia and Callimico goeldii are superficially similar in their use of predefined locomotor patterns but differ profoundly in many underlying details which reflect differences in postcranial morphology. Each uses pronograde arboreal quadrupedal walking, quadrupedal bounding, and vertical climbing with comparable frequency, and both shift to bounding while moving quadrupedally at high speeds. In walking, both species use a diagonal sequence gait. However, in Callimico the distance per bout traveled while walking or running is shorter than in L. rosalia and there is an emphasis on leaping (from a stationary position) and bounding-leaps (saltational extensions of pronograde quadrupedalism), in contrast with the basically quadrupedal style of L. rosalia. This dichotomy is consistent with anatomical specializations, such as forelimb elongation in Leontopithecus and hindlimb elongation in Callimico. In vivo hand- and footprint studies demonstrate grasping halluces in both species while walking. Limb stances in L. rosalia during “transaxial bounding” involve an overstriding hindlimb, a predominance of oblique rather than in-line travel, and unique hand and foot positions. Anatomically, this locomotor style may be associated with reduced dexterity of the elongate hands and a relatively short hallux. The captive locomotor profiles for both species probably reflect biased samples of the locomotor repertoire of their wild counterparts. Nevertheless, these data reflect species-specific integrations of locomotor behavior and morphology, and corroborate expectations of locomotor diversity among callitrichine primates, even those of similar body size. It is suggested, however, that conventional quantitative studies of locomotor profiles may prove inadequate for resolving subtle aspects of locomotor morphology and behavior. © 1994 Wiley-Liss, Inc.     

Locomotion and posture in Lagothrix lagotricha

This long-term study of woolly monkey (Lagothrix) locomotor and postural behaviour employs methods identical to those used during a previous study of the locomotion and posture of two species of Ateles, allowing a detailed comparison between the two genera, which are strong competitors in extensive parts of the Amazon basin and northern Andes. As in Ateles, Lagothrix locomotion can be divided into five patterns, based on limb usage: quadrupedal walking and running, suspensory locomotion, climbing, bipedalism (very rare in wild woolly monkeys) and leaping. Lagothrix differs from Ateles primarily in its greater reliance on quadrupedal locomotion during both travel and feeding and on its de-emphasis of the use of suspensory locomotion as compared to Ateles, while the use of climbing and leaping is roughly equal in the two genera. Lagothrix exhibits more generalised (primitive) locomotive behaviour in accordance with its morphology, in comparison to the more specialised Ateles. The generic differences reflect differences in habitat use and particularly foraging ecology.     

Investigating the form-function interface in African apes: Relationships between principal moments of area and positional behaviors in femoral and humeral diaphyses

Investigations of cross-sectional geometry in nonhuman primate limb bones typically attribute shape ratios to qualitative behavioral characterizations, e.g., leaper, slow climber, brachiator, or terrestrial vs. arboreal quadruped. Quantitative positional behavioral data, however, have yet to be used in a rigorous evaluation of such shape-behavior connections. African apes represent an ideal population for such an investigation because their relatedness minimizes phylogenetic inertia, they exhibit diverse behavioral repertoires, and their locomotor behaviors are known from multiple studies. Cross-sectional data from femoral and humeral diaphyses were collected for 222 wild-shot specimens, encompassing Pan paniscus and all commonly recognized African ape subspecies. Digital representations of diaphyseal cross sections were acquired via computed tomography at three locations per diaphysis. Locomotor behaviors were pooled broadly into arboreal and terrestrial categories, then partitioned into quadrupedal walking, quadrumanous climbing, scrambling, and suspensory categories. Sex-specific taxonomic differences in ratios of principal moments of area (PMA) were statistically significant more often in the femoral diaphysis than the humeral diaphysis. While it appears difficult to relate a measure of shape (e.g., PMA ratio) to individual locomotor modes, general locomotor differences (e.g., percentage arboreal vs. terrestrial locomotion) are discerned more easily. As percentage of arboreal locomotion for a group increases, average cross sections appear more circular. Associations between PMA ratio and specific locomotor behaviors are less straightforward. Individual behaviors that integrate eccentric limb positions (e.g., arboreal scrambling) may not engender more circular cross sections than behaviors that incorporate repetitive sagittal movements (e.g., quadrupedal walking) in a straightforward manner.