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A new fossil amniote from the Fossil Forest of Chemnitz (Sakmarian-Artinskian transition, Germany) is described as Ascendonanus nestleri gen. et sp. nov., based on five articulated skeletons with integumentary preservation. The slender animals exhibit a generalistic, lizard-like morphology. However, their synapsid temporal fenestration, ventrally ridged centra and enlarged iliac blades indicate a pelycosaur-grade affiliation. Using a renewed data set for certain early amniotes with a similar typology found Ascendonanus to be a basal varanopid synapsid. This is the first evidence of a varanopid from Saxony and the third from Central Europe, as well as the smallest varanopid at all. Its greatly elongated trunk, enlarged autopodia and strongly curved unguals, along with taphonomical observations, imply an arboreal lifestyle in a dense forest habitat until the whole ecosystem was buried under volcanic deposits. Ascendonanus greatly increases the knowledge on rare basal varanopids; it also reveals a so far unexpected ecotype of early synapsids. Its integumentary structures present the first detailed and soft tissue skin preservation of any Paleozoic synapsid. Further systematic results suggest a varanodontine position for Mycterosaurus, the monophyly of South African varanopids including Anningia and the distinction of a skeletal aggregation previously assigned to Heleosaurus, now renamed as Microvaranops parentis gen. et sp. nov. [ABSTRACT FROM AUTHOR]

The Clarkia lagerstätte (Latah Formation) of Idaho is well known for its beautifully preserved plant fossils as well as a fauna of insects and fish. Here we present the first known tetrapod fossil from these deposits. This specimen, recovered from the lower anoxic zone of the beds, is preserved as a carbonaceous film of a partial skeleton associated with a partial lower incisor and some tooth fragments. The morphology of the teeth indicates that the first tetrapod reported from Clarkia is a rodent. Its skeletal morphology as well as its bunodont and brachydont dentition suggests that it is a member of the squirrel family (Sciuridae). It is a large specimen that cannot be assigned to a known genus. Instead, it appears to represent the first occurrence of a new taxon with particularly gracile postcranial morphology likely indicative of an arboreal ecology. This new specimen is a rare glimpse into the poorly known arboreal mammal fossil record of the Neogene. It supports a greater taxonomic and ecological diversity of Miocene Sciuridae than previously recognized and offers new lines of inquiry in the paleoecological research enabled by the unique preservation conditions of the Clarkia biota. [ABSTRACT FROM AUTHOR]

Thoasia Liebke, 1939 and Straneotia Mateu, 1961 of the Cryptobatida group, subtribe Agrina, Lebiini, living in the Neotropics are diagnosed, described, and illustrated. Occurrences of known species ranges are limited to the northern and western Amazon Basin and Guyana Shield. The following species are described as new: Thoasia surinamensis Erwin & Aldebron, sp. n., Suriname, Thoasia pterosmaragdos Aldebron & Erwin, sp. n., French Guiana, Thoasia manu Erwin & Aldebron, sp. n., Ecuador, Perú; Straneotia cylindroceps Erwin & Aldebron, sp. n., French Guiana, Straneotia confundis Aldebron & Erwin, sp. n., Ecuador, and Straneotia moi Aldebron & Erwin, sp. n., French Guiana. Two of these species, Thoasia manu and Straneotia moi are known from adults collected by insecticidal fogging of lowland rainforest trees, and these trees are listed in their respective descriptions. The following species are redescribed: Thoasia rugifrons Liebke, 1939, French Guiana, Venezuela; Straneotia freyi Mateu, 1961, Brazil; Straneotia amazonica Mateu, 1961, Brazil. [ABSTRACT FROM AUTHOR]

It has long been accepted that hominids emerged during the Pliocene in a savannah environment in which a terrestrial quadruped gradually developed bipedal adaptations. However, data from the Late Miocene (i.e. 7–7.5 Ma), including detailed palaeontological and biogeochemical studies, suggest that our earliest Upper Miocene ancestors inhabited well-wooded to forested environments where they could have spent a certain amount of time in the trees. A plausible type of ecosystem in which upright posture and bipedal locomotion could have emerged is represented by Miombo Woodland, in which vertical arboreal supports predominate and trees are separated from each other by gaps. Subsequently hominids dispersed into the Savannah as accomplished bipeds, but retained the ability to climb trees. This scenario is compatible with the postcranial anatomy ofAustralopithecus, including its femoral elongation, body proportions, manual precision grip (also present in 6-million-year-oldOrrorin) and a non-prehensile hallux. [ABSTRACT FROM PUBLISHER]

The acacia rat Thallomys paedulcus is a small arboreal rodent, extensively dependent on Acacia sp. trees. In order to understand the arboreal locomotor adaptations of the species, we examined their gaits in arboreal locomotion (i.e. diagonality, duty factor, duty factor index, velocity, and stride length and frequency). For these purposes, we filmed 12 captive specimens on simulated arboreal substrates of variable sizes (2 mm, 5 mm, 10 mm, 25 mm) and inclinations (0° and 45°). Acacia rats employed slow, symmetrical gaits with lower diagonality on the smaller substrates, which were progressively substituted by faster, asymmetrical half-bounding gaits on larger substrates. In general, inclination had no impact on gait metrics, except that ascents were slower than horizontal locomotion. Velocity increase was regulated primarily due to an increase in stride frequency, a pattern encountered in many small mammals, although stride length contributed significantly as well. These locomotor adaptations serve as a behavioural mechanism to cope with the challenges of the arboreal milieu. They appear to provide stability and enable safe negotiation of arboreal substrates, ultimately leading to the successful exploitation of Acacia trees in their natural habitat. [ABSTRACT FROM AUTHOR]

Despite being known to exhibit arboreal behaviours, Kaloula pulchra, the banded bullfrog, is generally considered terrestrial in its habits and is well known for burrowing into substrate. Here we report seven observations, between October 2015 and March 2017, which document arboreal behaviors in banded bullfrogs in the Sakaerat Biosphere Reserve, Thailand. Our observations comprise the first record of banded bullfrogs predating invertebrates in an arboreal setting. Our observations of K. pulchra climbing large rain jars and subsequently becoming trapped inside also suggest a cause of death for this species. Additional surveys are needed to determine whether this phenomenon prevails throughout rural Thailand. [ABSTRACT FROM AUTHOR]

Upright bipedalism is a hallmark of hominin locomotion, however debates continue regarding the extent of arboreal locomotion and the nature of bipedalism practiced by early hominins. Pedal form and function play a prominent role in these debates, as the foot is the element that directly interacts with the locomotor substrate. Recent finds have substantially increased the availability of associated foot remains of early hominins and emphasized the enigmatic nature of the early evolution of human bipedalism. New discoveries of associated forefoot remains have afforded the opportunity to assess relative proportions across the forefoot of fossil hominins and illuminated the need for data on relative loading across the forefoot in extant hominoids. In order to provide functional data with which to examine the relationship between bony features and load distribution across the forefoot during climbing, we present the first analysis of plantar pressure distribution across the forefoot of chimpanzees climbing a vertical support. Chimpanzees load the medial metatarsals and first toe disproportionately during vertical climbing. Peak pressures on these elements occur at the end of stance phase during climbing and are higher than on any other elements of the foot. Toe pressures are considerably higher during vertical climbing than during knuckle-walking or movement on horizontal poles, supporting the notion that the plantarly-broad and dorsally-narrow metatarsal heads in chimpanzees and some early hominins are associated with close-packing of the metatarsophalangeal joint during climbing. [ABSTRACT FROM AUTHOR]

The link between laterality in humans and other primates is still hotly debated. Hylobatids have been rather neglected in this research area, yet they can provide important insights because: (1) they share with humans a complex vocal repertoire, which in humans is thought to be associated with brain hemispheric specialization and lateralized behaviors; (2) their adaptation to arboreality has produced unique postural constraints; (3) the little that is known about laterality in gibbons is contradictory (captive studies have provided conflicting results, while a field study on siamangs reported a population-level left-hand preference). To clarify this, we investigated hand preference in captive hylobatids [ n = 42; 22 siamangs ( Symphalangus syndactylus) and 20 gibbons ( Hylobates sp., Nomascus leucogenys)] in nine Japanese facilities. We had a large sample size, controlled for possible confounds (posture, enclosure limitations) and used a well-established testing protocol (tube task). Handedness indices calculated from raw frequencies and bouts were highly correlated and showed a significant left-hand skew, which is consistent with data from wild siamangs. Major differences between captive and wild siamangs were a larger number of ambiguously handed individuals, and no significant age-related variation in captivity. The use of the index finger elicited a much more strongly lateralized response than the thumb. These results confirmed a left-hand preference in siamangs, but were equivocal in other hylobatids, and suggest selective pressures that may have acted on the highly arboreal hylobatids to favor handedness. Our study also indicates factors that might explain the discrepancy in the literature between handedness studies on captive and wild primate populations. [ABSTRACT FROM AUTHOR]

Although investigations of forelimb characteristics are central to therian evolutionary studies, the functional origins of forearm pronation are neglected. However, recent research based on bipedal manipulations strongly suggests that proximal radioulnar joint mobility is highly conserved in tetrapods. This new information calls for a replication of previously published physical simulations of forearm bone movements, to investigate whether active therian pronation/supination evolved from the plesiomorphic mechanism via which locomotor-induced torsion is passively alleviated during forelimb retraction. Preliminary results using representative extant and extinct tetrapod forelimb elements are supportive, and also offer insight into why another overlooked forearm trait, osteological full pronation (mechanically aligned elbow and wrist/finger joints), evolved only in therians and chameleons. During forelimb retraction in tetrapods with unfused radii/ulnae, the radius unexpectedly remains fixed in place as a functional complex with the firmly planted manus/carpus, which the ulnar complex (ulna/humerus) displaces relative to. Therefore, the highly conserved functional morphology of the tetrapod forearm indicates that enhanced therian manual dexterity, which emphasizes isolated radial movements bipedally, was preceded by the locomotor evolution of ulnar supination relative to the radius quadrupedally. This counterintuitive information indicates that the traditional hypothesis, that therian pronation/supination evolved arboreally to amplify radial mobility, requires modification. The authors propose that proximal long-axis rotations of the therian ulnar complex co-evolved with osteological full pronation during a period of arboreal, chameleon-like locomotion, to continue allowing torsion at a reinforced proximal radioulnar joint. These adaptations were later or simultaneously co-opted for object manipulation using active radioulnar pronation/supination. [ABSTRACT FROM AUTHOR]

Vertical stratification of the arboreal habitat allows the coexistence of several species in a given area, because the complex arboreal strata can be used in different ways by arboreal and scansorial mammals. The present report experimentally investigated the gait metrics on different arboreal substrates, of three sympatric rodents living in a deciduous forest in Poznań, Poland. Arboreal locomotion was compared between the burrowing striped field mouse, Apodemus agrarius , the scansorial bank vole, Myodes glareolus , and the more arboreal yellow-necked mouse, Apodemus flavicollis . We filmed two wild-caught individuals from each species walking on four different substrate diameters (2 mm, 5 mm, 10 mm, 25 mm) and three different inclinations (45° descending, horizontal, 45° ascending) at 240 fps and collected a set of gait parameters from a total of 273 complete cycles. Our results did not demonstrate clear relationships between arboreal locomotion and the ecology of the three species. Only A. flavicollis exhibited locomotor features partly associated with arboreal competence, including lower velocity and diagonality on narrow substrates and asymmetrical gaits on wider ones. On the other hand, the two Apodemus species, despite their different ecologies, shared a few locomotor similarities, such as velocity regulation primarily by stride frequency, and similar effects of substrate size and inclination on diagonality, duty factor, and duty factor index indicating the possibility of a phylogenetic signal. Because the selected gait parameters provided limited insight into the ability of small mammals to move competently through an arboreal habitat, these findings indicate that the relationship between behaviour and ecology is complex. [ABSTRACT FROM AUTHOR]

A central question in biology is how animals successfully behave under complex natural conditions. Although changes in locomotor behaviour, motor control and force production in relation to incline are commonly examined, a wide range of other factors, including a range of perch diameters, pervades arboreal habitats. Moving on different substrate diameters requires considerable alteration of body and limb posture, probably causing significant shifts in the lengths of the muscle-tendon units powering locomotion. Thus, how substrate shape impacts in vivo muscle function remains an important but neglected question in ecophysiology. Here, we used high-speed videography, electromyography, in situ contractile experiments and morphology to examine gastrocnemius muscle function during arboreal locomotion in the Cuban knight anole, Anolis equestris. The gastrocnemius contributes more to the propulsive effort on broad surfaces than on narrow surfaces. Surprisingly, substrate inclination affected the relationship between the maximum potential force and fibre recruitment; the trade-off that was present between these variables on horizontal surfaces became a positive relationship on inclined surfaces. Finally, the biarticular nature of the gastrocnemius allows it to generate force isometrically, regardless of substrate diameter and incline, despite the fact that the tendons are incapable of stretching during cyclical locomotion. Our results emphasize the importance of considering ecology and muscle function together, and the necessity of examining both mechanical and physiological properties of muscles to understand how animals move in their environment. [ABSTRACT FROM AUTHOR]

Across vertebrate diversity, limb bone morphology is typically expected to reflect differences in the habitats and functional tasks that species utilize. Arboreal vertebrates are often recognized to have longer limbs than terrestrial relatives, a feature thought to help extend the reach of limbs across gaps between branches. Among terrestrial vertebrates, longer limbs can experience greater bending moments that might expose bones to a greater risk of failure. However, changes in habitat or behavior can impose changes in the forces that bones experience. If locomotion imposed lower loads in trees than on the ground, such a release from loading demands might have produced conditions under which potential constraints on the evolution of long limbs were removed, making it easier for them to evolve in arboreal species. We tested for such environmental differences in limb bone loading using the green iguana (Iguana iguana), a species that readily walks over ground and climbs trees. We implanted strain gauges on the humerus and femur, and then compared loads between treatments modeling substrate conditions of arboreal habitats. For hindlimbs, inclined substrate angles were most correlated with strain increases, whereas the forelimbs had a similar pattern but of lesser magnitude. Unlike some other habitat transitions, these results do not support biomechanical release as a mechanism likely to have facilitated limb elongation. Instead, limb bone adaptations in arboreal habitats were likely driven by selective pressures other than responses to skeletal loading., Competing Interests: Competing interests The authors declare no competing or financial interests., (© 2023. Published by The Company of Biologists Ltd.)

The gecko Mediodactylus kotschyi is considered rare in mainland Greece, yet it is very abundant on the Aegean islands. It has been thought to be saxicolous throughout much of its range. In a recent survey on the Peloponnese peninsula, however, we encountered it mainly on trees, and with higher frequency than previously reported. We combined our observations of localities in which we detected this gecko, and places where we failed to detect it, with data about its occurrence from the literature and museum collections. We posited two hypotheses as possible causes for the apparent relative scarcity of M. kotschyi in the Peloponnese: that it is associated with low precipitation and that it has an aversion to limestone rock. We predicted that M. kotschyi would be more likely to be found in arid places and where limestone is not the dominant type of rock, since it has been reported that this substrate is less suitable for this species. Moreover, we predicted that geckos occurring in limestone regions would be found on trees rather than under rocks. Geckos were indeed found mainly in the more arid parts of the Peloponnese, but not exclusively so. We found no evidence of limestone avoidance. We suggest that, because M. kotschyi is better known as being mostly saxicolous over most of its range, and exclusively so on the Greek islands, in the Peloponnese the search for this species has been restricted to a single habitat type, i.e., under rocks and not on trees. It may thus inhabit more localities in the Peloponnese and be more abundant there than has previously been thought. [ABSTRACT FROM AUTHOR]

Despite the high mechanical demands associated with climbing, the ability to ascend vertically has evolved independently in most major animal lineages. However, little is known about the kinetics, mechanical energy profiles or spatiotemporal gait characteristics of this locomotor mode. In this study, we explored the dynamics of horizontal locomotion and vertical climbing on both flat substrates and narrow poles in five Australian green tree frogs (Ranoidea caerulea). Vertical climbing is associated with slow, deliberate movements (i.e. reduced speed and stride frequency and increased duty factors) and propulsive fore-aft impulses in both the forelimb and hindlimb. By comparison, horizontal walking was characterized by a braking forelimb and a propulsive hindlimb. In the normal plane, tree frogs mirrored other taxa in exhibiting a net pulling forelimb and a net pushing hindlimb during vertical climbing. In terms of mechanical energy, tree frogs matched theoretical predictions of climbing dynamics (i.e. the total mechanical energetic cost of vertical climbing was predominantly driven by potential energy, with negligible kinetic contributions). Utilizing power as a means of estimating efficiency, we also demonstrate that Australian green tree frogs show total mechanical power costs only slightly above the minimum mechanical power necessary to climb, highlighting their highly effective locomotor mechanics. This study provides new data on climbing dynamics in a slow-moving arboreal tetrapod and raises new testable hypotheses about how natural selection can act upon a locomotor behavior that is notably constrained by external physical forces., Competing Interests: Competing interests The authors declare no competing or financial interests., (© 2023. Published by The Company of Biologists Ltd.)

Regionalization of the vertebral column can help animals adapt to different kinds of locomotion, including arboreal locomotion. Although functional axial regionalization has been described in both chameleons and arboreal mammals, no morphological basis for this functional regionalization in chameleons has been proposed. However, recent studies have described regionalization in the presacral vertebral column of other extant squamates. To investigate possible morphological regionalization in the vertebral column of chameleons, we took morphometric measurements from the presacral vertebrae of 28 chameleon species representing all extant chameleon genera, both fully arboreal and ground-dwelling, and performed comparative analyses. Our results support chameleons exhibiting three or four presacral morphological regions that correspond closely to those in other sauropsids, but we detected evolutionary shifts in vertebral traits occurring in only arboreal chameleons. Specifically, the anterior dorsal region in arboreal chameleons has more vertically oriented zygapophyseal joints, predicting decreased mediolateral flexibility. This shift is functionally significant because stiffening of the anterior thoracic vertebral column has been proposed to help bridge gaps between supports in primates. Thus, specialization of existing morphological regions in the vertebral column of chameleons may have played an important role in the evolution of extreme arboreal locomotion, paralleling the adaptations of arboreal primates., Competing Interests: We declare we have no competing interests., (© 2023 The Authors.)

Invasive species pose one of the greatest threats to biodiversity. This study investigates the extent to which human disturbance to natural ecosystems facilitates the spread of non-native species, focusing on a small mammal community in selectively logged rain forest, Sabah, Borneo. The microhabitat preferences of the invasive Rattus rattus and three native species of small mammal were examined in three-dimensional space by combining the spool-and-line technique with a novel method for quantifying fine-scale habitat selection. These methods allowed the detection of significant differences for each species between the microhabitats used compared with alternative, available microhabitats that were avoided. Rattus rattus showed the greatest preference for heavily disturbed habitats, and in contrast to two native small mammals of the genus Maxomys, R. rattus showed high levels of arboreal behavior, frequently leaving the forest floor and traveling through the understory and midstory forest strata. This behavior may enable R. rattus to effectively utilize the complex three-dimensional space of the lower strata in degraded forests, which is characterized by dense vegetation. The behavioral flexibility of R. rattus to operate in both terrestrial and arboreal space may facilitate its invasion into degraded forests. Human activities that generate heavily disturbed habitats preferred by R. rattus may promote the establishment of this invasive species in tropical forests in Borneo, and possibly elsewhere. We present this as an example of a synergistic effect, whereby forest disturbance directly threatens biodiversity and indirectly increases the threat posed by invasive species, creating habitat conditions that facilitate the establishment of non-native fauna. [ABSTRACT FROM AUTHOR]

Nearly all primates are ecologically dependent on trees, but they are nonetheless found in an enormous range of habitats, from highly xeric environments to dense rainforest. Most primates have a relatively 'generalised' skeleton, enabling locomotor flexibility and facilitating other crucial functions, such as manual foraging and grooming. This paper explores the associations between habitat, locomotion and morphology in the forelimbs of cercopithecids (Old World monkeys), contextualising their skeletal ecomorphological patterns with those of other mammals, and complementing functional morphological analyses with phylogenetic comparative techniques. The ecomorphological signals present in the generalised primate postcranium, and how an ancestral arboreal 'bauplan' might be modified to incorporate terrestriality or exploit distinct arboreal substrates, are investigated. Analysis of ecomorphological variation in guenons indicates that terrestrial Chlorocebus species retain core elements of a general guenon form, with modifications for terrestriality that vary by species. Adaptation to different modes of arboreality has also occurred in Cercopithecus. The considerable morphological similarity in the guenons sampled emphasises the importance of generality in the primate postcranium - much forelimb variation appears to have emerged stochastically, with a smaller number of traits having a strong functional signal. Analysis of a broader sample of cercopithecids and comparison with felids, suids and bovids indicates that although the cercopithecid humerus has functional morphological signals that enable specimens to be assigned with a reasonable degree of certainty to habitat groups, there is considerable overlap in the specimens assigned to each habitat group. This probably reflects ecological dependence on trees, even in predominantly terrestrial species, as well as the multiple functions of the forelimb and, in some cases, wide geographic distributions that promote intraspecific variation. The use of phylogenetic correction reduced the discriminatory power of the models, indicating that, like allometry, phylogeny contains important ecomorphological information, and should not necessarily be factored out of analyses. [ABSTRACT FROM AUTHOR]

Gravity imposes potentially important constraints on blood circulation in tall or elongate animals during upright posture or climbing. Upright postures create vertical gradients of gravitational (=hydrostatic) pressures within circulatory vessels. In terrestrial animals, this pressure potentially induces blood pooling and oedema in dependent (inferior) tissues and, secondarily, decreases blood volume reaching the head and vital organs. Arboreal snakes exhibit a suite of adaptations for countering the effects of gravity on blood circulation, including relatively non-compliant tissue compartments in the tail. However, patterns of tail length related to arboreal habitats and gravity have not been previously studied. Here, we test the hypothesis that arboreal snakes have relatively longer tails than non-climbing species, and we interpret the results within the context of adaptation to gravity stress., Length data were obtained for 226 snake species, 139 genera and 15 snake families assigned to three broad gravitational habitat categories (G-habitats: stenotopically arboreal, eurytopically arboreal/terrestrial and non-scansorial). We constructed a composite phylogenetic tree and quantified the relationships between snake morphology and G-habitat using conventional regression analysis of species data and regressions of phylogenetically independent contrasts., Mean relative tail length ( RTL) increased and mean relative snout-vent length decreased with increasing arboreality among the three G-habitats. However, mean total body length ( TL) was not different between the two arboreal G-habitats., Snakes with longer RTLs have a higher percentage of elongate blood vessels contained within the relatively non-compliant integument of the tail, which mitigates postural blood pooling experienced during climbing. TL in adult female arboreal snakes is hypothesized to be an evolutionary trade-off between demands for a longer tail to enhance cardiovascular performance and the length of body cavity to provide space for young., Our results complement previous studies correlating RTL with arboreal habitat use, in addition to physiological experiments quantifying the effects of gravity on blood flow in snakes. These results provide evidence that long RTLs of arboreal snakes function, at least in part, as an adaptive response to cardiovascular stresses on blood circulation imposed by gravity. Selection on tail length related to other factors seems less likely, but is in need of further investigation. [ABSTRACT FROM AUTHOR]

Evaluation of the fundamental niche under controlled conditions can provide relevant information about physiological, evolutionary, and ecological aspects of an organism, without the influence of external factors. We investigated how allometric, phylogenetic, and adaptive components contribute to arboreal walking performance by 7 sigmodontine rodents of the Brazilian savanna (Cerrado). We captured the rodents in the field and evaluated their performances by measuring stride length, stride frequency, and velocity on 5 horizontal supports: flat board and cylindrical plastic tubes with diameters of 5.0, 3.5, 2.5, and 2.0 cm. Arboreal rodents exhibited higher velocities than terrestrial species by increasing stride frequency and decreasing stride length on supports with smaller diameters. However, terrestrial species decreased both stride frequency and stride length or tended to maintain stride length and vary stride frequency. Our results reveal a strong association between realized arboreal walking performances (as inferred by proportion of arboreal captures) and stride length and frequency. However, performance metrics were weakly related to body mass and exhibited no phylogenetic effects. Our results are consistent with the hypothesis that dynamically stable arboreal walking is facilitated by increased velocity. Arboreal walking performance is likely related to ecological factors rather than phylogenetic constraints. [ABSTRACT FROM AUTHOR]

The medial cuneiform, namely the curvature and angulation of its distal facet with metatarsal 1, is crucial as a stabilizer in bipedal locomotion and an axis upon which the great toe medially deviates during arboreal locomotion in extant apes. Previous work has shown that facet curvature and angulation in adult dry-bone specimens can distinguish African apes from Homo , and can even distinguish among species of Gorilla . This study provides the first ontogenetic assessment of medial cuneiform curvature and angulation in juvenile (n = 68) and adult specimens (n = 102) using computed tomography in humans and extant ape specimens, including Pongo . Our data find that modern human juveniles initially have a convex and slightly medially oriented osseous surface of the developing medial cuneiform distal facet that flattens and becomes more distally oriented with age. The same pattern (though of a different magnitude) occurs developmentally in the chimpanzee medial cuneiform, but not in Gorilla or Pongo , whose medial cuneiform facet angulation remains unchanged ontogenetically. These data suggest that the medial cuneiform ossifies in a distinguishable pattern between Pongo , Gorilla , Pan , and Homo , which may in part be due to subtle differences in the loading environment at the hallucal tarsometatarsal joint—a finding that has important implications for interpreting fossil medial cuneiforms. [ABSTRACT FROM AUTHOR]

In this paper, I describe the food-dropping behavior of western lowland gorillas observed in Moukalaba-Doudou National Park, Gabon. I collected observational data of gorillas eating in trees, and recorded whether any individuals were positioned under the same tree. In 22 of the 24 cases of individuals being present under a tree, I observed the gorilla in a tree dropping food to the individual below. In most cases, the recipient was a silverback or an elder half-sibling of the dropper. The dropper's elder full-sibling was never a recipient. The food-dropping behavior of Moukalaba western lowland gorillas is likely due to a combination of factors: their frugivory, arboreality, large body size, and the scarcity of terrestrial herbs. It is difficult for multiple gorillas to simultaneously feed in the same tree. Under such limitations, younger gorillas face difficulties in defending their feeding patches from older individuals. Nearly 90 % of the recipients were older than the food droppers. Furthermore, food droppers were significantly younger than non-food droppers who simultaneously fed on the same tree, and most-food recipients were significantly older than least-food recipients on the ground. Food dropping may, therefore, be a tactic employed by younger gorillas to defend a feeding site from older individuals. This study suggests that food dropping may reduce feeding contest competition in a gorilla group in Moukalaba. This is a preliminary study that indicates that food dropping may be intentionally used as a way to reduce feeding competition; nevertheless, further studies are needed. [ABSTRACT FROM AUTHOR]

Abstract: Walking and running have dominated the literature on human locomotor evolution at the expense of other behaviors with positive and negative fitness consequences. For example, although modern hunter-gatherers frequently climb trees to obtain important food resources in the canopy, these behaviors are seldom considered within the existing framework of primate positional behavior. As a result, inferences about the arboreal performance capabilities of fossil hominins based on a resemblance to humans may be more complicated than previously assumed. Here we use ethnographic reports of human tree climbing to critically evaluate hypotheses about the performance capabilities of humans in trees compared with other primates. We do so by reviewing the ecological basis of tree climbing behavior among hunter-gatherers and the diversity of human climbing techniques and styles. Results suggest that the biological and adaptive significance of human climbing has been underestimated, and that some humans are surprisingly competent in trees, particularly during vertical climbing and activities in the central core of trees. We conclude that while hominins evolved enhanced terrestrial locomotor performance through time, such shifts may have imposed only minor costs on vertical climbing abilities. The diversity of the locomotor repertoire of modern humans must therefore be taken into account when making form-function inferences during the behavioral reconstruction of fossil hominins. [Copyright &y& Elsevier]

ABSTRACT Gorillas occupy a variety of habitats from the west coast to eastern central Africa. These habitats differ considerably in altitude, which has a pronounced effect on forest ecology. Although all gorillas are obligate terrestrial knuckle-walking quadrupeds, those that live in lowland habitats eat fruits and climb more often than do those living in highland habitats. Here we test the hypothesis that gorilla talus morphology falls along a morphocline that tracks locomotor function related to a more inverted or everted foot set. This proposed morphocline predicts that gorillas living in lowland habitats may have a talocrural joint configured to facilitate a more medially oriented foot during climbing, suggesting that they may be more adaptively committed to arboreality than gorillas living in highland habitats. To quantify the relative set of the foot in gorillas, we chose two three-dimensional measurements of the talocrural joint: mediolateral curvature of the trochlea and relative surface area of the lateral malleolus. Our results show that, in comparison to their eastern counterparts, western gorillas have talar features that reflect a more medially directed sole of the foot. This morphology likely facilitates foot placement in a wider range of positions and minimization of shearing stresses across the joint when the foot is loaded on more curved or vertically oriented substrates as occurs during climbing and other arboreal behaviors. In contrast, eastern gorilla talar morphology is consistent with habitual placement of the foot with the sole directed more inferiorly, suggesting more effective loading during plantigrade push-off on terrestrial substrates. Am J Phys Anthropol 153:526-541, 2014. © 2013 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Hypotheses for the origin and maintenance of sexual size dimorphism ( SSD) fall into three primary categories: (i) sexual selection on male size, (ii) fecundity selection on female size and (iii) ecological selection for gender-specific niche divergence. We investigate the impact of these forces on SSD evolution in New World pitvipers (Crotalinae). We constructed a phylogeny from up to eight genes (seven mitochondrial, one nuclear) for 104 species of NW crotalines. We gathered morphological and ecological data for 82 species for comparative analyses. There is a strong signal of sexual selection on male size driving SSD, but less evidence for fecundity selection on female size across lineages. No support was found for allometric scaling of SSD (Rensch's rule), nor for directional selection for increasing male size (the Fairbairn-Preziosi hypothesis) in NW crotalines. Interestingly, arboreal lineages experience higher rates of SSD evolution and a pronounced shift to female-biased dimorphism. This suggests that fecundity selection on arboreal females exaggerates ecologically mediated dimorphism, whereas sexual selection drives male size in terrestrial lineages. We find that increasing SSD in both directions (male- and female-biased) decreases speciation rates. In NW crotalines, it appears that increasing magnitudes of ecologically mediated SSD reduce rates of speciation, as divergence accumulates within species among sexes, reducing adaptive divergence between populations leading to speciation. [ABSTRACT FROM AUTHOR]

Recently proposed ancestral locomotor and morphological ‘stages’ leading to the evolution of primates have emphasized small body size, and a transition from a clawed non-grasping stage, to a clawed, grasping stage with clawless opposable hallux, to a fully-nailed primate with grasping extremities. This evolutionary transition was presumably associated with frequent use of the small branch niche. To model elements of these evolutionary transitions, we investigate how body size, substrate size, substrate orientation and grasping morphology interact to influence quadrupedal kinematics within and between ontogenetic samples of two small-bodied marsupials, one arboreal (Petaurus breviceps) and the other mainly terrestrial (Monodelphis domestica). Longitudinal morphometric and kinematic data were collected from four juvenile P. breviceps (33–75 g) and two juvenile M. domestica (18–95 g) walking across poles of three diameters (2.5, 1.0, and 0.5 cm) and three orientations (horizontal, 30° incline, 30° decline). The two species responded similarly to some substrate conditions, but diverged in response to others. Kinematic divergence between the two species reflects Monodelphis' relatively shorter digits, reduced grasping ability and greater need for stabilizing mechanisms on narrow substrates. At a given relative body size or pole orientation, Monodelphis used higher limb duty factors, more limbs in support per stride, lower limb phases, and in some conditions, faster speeds compared with Petaurus. Interspecific differences were the least distinct on declined poles, highlighting the particular challenge of this substrate condition, even for arboreally adapted species. Small-bodied, arboreal primate ancestors would likely have employed the kinematic mechanisms common to our model taxa, but those with enhanced grasping adaptations would most likely not have required the increased level of stabilizing mechanisms exhibited by Monodelphis. Thus, using these two species as locomotor models has underscored the functional importance of grasping extremities in primate origins, even if ancestral primates were very small in body size. [ABSTRACT FROM AUTHOR]

The ability to securely grasp substrates of variable diameter is critical to arboreal animals. Arboreal specialists have emerged across several vertebrate lineages - including mammals, lizards and amphibians - and several attempts have been made to quantify their grasping performance, by measuring either gripping (i.e. forces generated about an object or substrate enclosed within the digits) or pulling (i.e. the ability to resist being removed from a substrate) forces. In this study, we present data on both pulling and gripping performance across a range of substrate diameters (0.5-17.5 mm) within a model parrot species (Agapornis roseicollis). Parrots represent an ancient arboreal lineage, allowing us to compare their abilities with those of arboreal specialists within other tetrapod groups. Data were collected using 3D-printed perches of variable diameter, and forces were registered using either an AMTI low-load force plate (grip force) or a Harvard Apparatus portable strength tester (pull force). Gripping forces peaked at a 5 mm diameter perch, while pulling forces were greatest at a 2.5 mm diameter. All forces strongly diminished above 10 mm size, suggesting grip force is optimized when utilizing small perches, a finding which corresponds to observational studies of preferential perching habits among free-ranging parrots. Relative grasping performance (adjusted for body size) in parrots is roughly equivalent to that of other arboreal specialists from other tetrapod lineages, but low when compared with that of raptorial birds that utilize their feet during aerial prey capture. Further taxonomic sampling is encouraged to contextualize how grasping performance varies in an adaptive evolutionary context., Competing Interests: Competing interests The authors declare no competing or financial interests., (© 2022. Published by The Company of Biologists Ltd.)

Abstract: This paper presents an analysis of metatarsal torsion in apes, cercopithecoids and humans, compares australopiths with these species, and discusses their inferred foot morphology and function relative to prehensility, arboreality and the presence or absence of a longitudinal arch. Our results show that locomotor modes are reflected in metatarsal torsion values. Apes, which climb vertically with their foot inverted, have hallucal metatarsal heads that are turned toward the other toes and lateral toes that are inverted. Cercopithecoids, which tend to orient their feet in an axis more parallel to the line of motion, present signs of prehensility by having inverted 2nd metatarsals that oppose the hallux, while their two lateral-most metatarsals are strongly everted. Humans, with their rigid feet and longitudinal arches, have all toes that present their plantar surface toward the ground, resulting in hallucal and 2nd metatarsals that are relatively untwisted and the others that are strongly everted. Humans are different from all taxa only for the 2nd and 3rd metatarsal. It is hypothesized that the untwisted 2nd metatarsal reflects the lack of digit opposability of the medial foot and the strongly everted 3rd metatarsal reflects the longitudinal arch. Australopithecus afarensis was characterized by an everted lateral foot, the prerequisite for the development, but not necessarily an indicator, of a longitudinal arch. In Australopithecus africanus, torsion of fragmentary and complete 1st, 2nd, 3rd and 5th metatarsals suggest that the species did not have a foot with monkey- or ape-like prehensile capabilities and did not have a human-like longitudinal arch. In the Swartkrans remains, torsion is consistent with an unprehensile foot. The morphology of the fossils indicates that there was strong selection to orient the plantar surface of the toes facing the ground at the expense of a grasping foot and inversion ability. [Copyright &y& Elsevier]

The Brown Vine snake, Oxybelis aeneus (Wagler, 1824), is widely distributed from the United States to Argentina. 113 specimens encountered in the field and 39 individuals from scientific collections were analyzed and we determined patterns of diet, habitat use, and daily and seasonal activity. Oxybelis aeneus can be found to be active year round, especially during the dry and warmer months. Daily temperature poorly describes its activity as it seems to be more active around 31 to 35°C. During the hours of inactivity the species tends to chose higher branches than when active. The snakes choose spiny trees as retreat sites and spineless trees as foraging sites. We suggest that the high abundance of O. aeneus makes it an appropriate model organism for studies on activity patterns of snakes in semi-arid environments. [ABSTRACT FROM AUTHOR]

Abstract: The genus Mesopithecus is well represented in the late Miocene of Greece by several recognized species. The present paper investigates functional aspects of the humeri of Mesopithecus delsoni/pentelicus, M. pentelicus and M. aff. pentelicus of several Turolian sites from central and northern Greece, using multivariate approaches. For these purposes, we selected significant humeral functional features, which were represented by 23 linear dimensions and three angles on 14 fossil humeri and 104 humeri from 10 genera and 22 species of extant African and Asian Colobines. All size-adjusted measurements were examined through a principal components analysis, followed by a discriminant function analysis, and a canonical variates analysis. All analyses revealed that the selected characters were able to discriminate between extant colobine genera. Functional groups, such as arboreal walking/climbing, arboreal walking/suspensory and semi-terrestrial walking, were set apart from a central cluster formed by the arboreal walking and arboreal walking/terrestrial groups. This cluster also grouped the three studied Mesopithecus species, which were mainly classified as arboreal walkers with significant terrestrial activities. These observations match with paleoenvironmental reconstructions and the suggested opportunistic feeding habits. Moreover, the overall arboreal/terrestrial locomotor tendencies of these fossil forms are discussed in relation to their earlier migration from Africa and later dispersal to eastern and southern Asia. [Copyright &y& Elsevier]

Arboreal mammals face unique challenges to locomotor stability. This is particularly true with respect to juveniles, who must navigate substrates similar to those traversed by adults, despite a reduced body size and neuromuscular immaturity. Kinematic differences exhibited by juveniles and adults on a given arboreal substrate could therefore be due to differences in body size relative to substrate size, to differences in neuromuscular development, or to both. We tested the effects of relative body size and age on quadrupedal kinematics in a small arboreal marsupial (the sugar glider, Petaurus breviceps; body mass range of our sample 33-97g). Juvenile and adult P. brevlceps were filmed moving across a flat board and three poles 2.5, 1.0 and 0.5 cm in diameter. Sugar gliders (regardless of age or relative speed) responded to relative decreases in substrate diameter with kinematic adjustments that promote stability; they increased duty factor, increased the average number of supporting limbs during a stride, increased relative stride length and decreased relative stride frequency. Limb phase increased when moving from the flat board to the poles, but not among poles. Compared with adults, juveniles (regardless of relative body size or speed) used lower limb phases, more pronounced limb flexion, and enhanced stability with higher duty factors and a higher average number of supporting limbs during a stride. We conclude that although substrate variation in an arboreal environment presents similar challenges to all individuals, regardless of age or absolute body size, neuromuscular immaturity confers unique problems to growing animals, requiring kinematic compensation. [ABSTRACT FROM AUTHOR]

The article discusses issues in the origin of human bipedalism and its importance in the evolution of mankind as of January 2012. Also cited are the various discoveries of fossil hominoid, including the Orrorin tugenensis in Kenya, the Ardipithecus kadabba in Ethiopia, and the Sahelanthropus tchadensis in Chad. Also cited is a study by anatomist Edward Tyson on the anatomies of chimpanzee and humans.

Abstract: Sixteen wood mice Apodemus sylvaticus were radio-tracked in a Mediterranean cork oak agro-forestry-system to describe their spatial distribution and organisation as well as their use of different habitat components. Our study, the first to analyse these features of wood mouse spatial ecology in Mediterranean agro-forestry environments using radio-tracking, showed a high variability in home ranges sizes reaching a mean values of 1.124±0.925ha (mean±sd), with no inter-sexual differences (8 males and 8 females tracked in March and June 2008). The extent to which different habitat components were used by wood mice varied significantly (−N ln λ =22.837, P <0.0001, n =6): while cork oak forests without understory were selected by both sexes equally in core areas (−N ln λ =32.361, P <0.0001, n =6), we also found evidence for a female-driven selection for home ranges to be located in olive groves (−N ln λ =59.949, P <0.0001, n =6), and movements to be set within cork oak forests with understory (−N ln λ =15.091, P <0.05, n =6). This habitat preference appears to result from the need of females to ensure access to sufficient food resources, the need of males to ensure access to females, and the need of both sexes for cover protection from predators. Moreover, we also show that the use of arboreal strata, most probably to access food, may also be an important factor to consider in analysing habitat use by wood mice. Implications of the recent evolution of this agro-silvo-pastoral system to the species ecology are emphasized. [Copyright &y& Elsevier]

Abstract: Locomotor features shared by arboreal marsupials and primates are frequently cited as a functional complex that evolved in the context of a “fine branch niche.” Adaptation to a fine branch niche cannot be understood without considering that small and large arboreal mammals may differ in their biomechanical response to a given branch size. We tested the effects of substrate diameter and orientation on quadrupedal kinematics in a small arboreal marsupial (the sugar glider, Petaurus breviceps). P. breviceps individuals were filmed moving across a flat horizontal surface and on horizontal, inclining and declining poles of diameter 2.5, 1.0, and 0.5cm. Gait frequencies, limb phases, speeds and duty factors were compared across substrate conditions. P. breviceps had a clear preference for lateral sequence/diagonal couplets gaits, regardless of substrate type, diameter or orientation. Limb phase was significantly influenced by substrate type (higher limb phases on poles vs. the flat surface) and by orientation (higher limb phases on inclined vs. horizontal poles), but was not influenced by pole diameter. Speed was lowest on declines, and duty factors (at a given speed) were highest on the flat board, smallest pole, and on declines. P. breviceps exhibited some parallels, but also some departures from the characteristic patterns of other arboreal marsupials and primates. Notably, limb phase values, on average, remained lower in P. breviceps than those recorded for primates or other arboreal marsupials. We suggest that arboreal mammals of different body sizes may use dissimilar, but apparently equally successful strategies for navigating a “fine branch niche.” [Copyright &y& Elsevier]

The Pale-headed Snake, Hoplocephalus bitorquatus (Jan 1859), is a slender-bodied, arboreal, venomous snake that is widely, but patchily, distributed through coastal and inland eastern Australia. We summarise existing knowledge on the conservation status and the ecology of this taxon, and provide original data based on fieldwork at a study site on the Namoi River (a river red gum - coolabah woodland). Four radio-tracked snakes spent long periods hidden within tree hollows, usually in Coolabah Trees. The telemetered snakes moved infrequently, with one gravid female remaining within the same tree for 61 days. Overall, strong similarities are evident between the Pale-headed Snake and two congeneric species that have attracted more detailed previous research. Those similarities, and the range of threatening processes affecting inland riparian ecosystems, suggest that the Pale-headed Snake may be of significant conservation concern and thus, warrant more intensive study. [ABSTRACT FROM AUTHOR]

Abstract: The adoption of a specific gait sequence pattern during symmetrical locomotion has been proposed to have been a key advantage for the exploitation of the fine branch niche in early primates. Diverse aspects of primate locomotion have been extensively studied in technically equipped laboratory settings, but evolutionary conclusions derived from these investigations have rarely been verified in wild primates. Bridging the gap from the lab to the field, we conducted an actual performance determination of symmetrical gaits in two free-ranging tamarin species (Saguinus mystax and Saguinus fuscicollis) of Amazonian Peru by analyzing high-speed video recordings of naturally occurring locomotor bouts. Tamarins arguably represent viable models for aspects of early primate locomotion. We tested three specific hypotheses derived from laboratory studies to test for the influence of support size and orientation and to gain further insight into the functional significance of primate gait sequence patterns: (1) The tamarins utilize symmetrical gaits at a higher rate on small supports than on larger ones. (2) During symmetrical locomotion on small supports, diagonal sequences are utilized at a higher rate than on larger supports. (3) On inclines, diagonal sequences are predominantly used and on declines, lateral sequences are predominantly used. Our results corroborated hypotheses 1 and 3. We found no clear support for hypothesis 2. In conclusion, our results add to the notion that primate gait plasticity, rather than uniform adoption of diagonal sequence gaits, enabled early primates to accommodate different support types and effectively exploit the small branch niche. [Copyright &y& Elsevier]

Primates display high forelimb compliance (increased elbow joint yield) compared to most other mammals. Forelimb compliance, which is especially marked among arboreal primates, moderates vertical oscillations of the body and peak vertical forces and may represent a basal adaptation of primates for locomotion on thin, flexible branches. However, Larney and Larson (Am J Phys Anthropol 125 [2004] 42-50) reported that marsupials have forelimb compliance comparable to or greater than that of most primates, but did not distinguish between arboreal and terrestrial marsupials. If forelimb compliance is functionally linked to locomotion on thin branches, then elbow yield should be highest in marsupials relying on arboreal substrates more often. To test this hypothesis, we compared forelimb compliance between two didelphid marsupials, Caluromys philander (an arboreal opossum relying heavily on thin branches) and Monodeiphis domestica (an opossum that spends most of its time on the ground). Animals were videorecorded while walking on a runway or a horizontal 7-mm pole. Caluromys showed higher elbow yield (greater changes in degrees of elbow flexion) on both substrates, similar to that reported for arboreal primates. Monodeiphis was characterized by lower elbow yield that was intermediate between the values reported by Larney and Larson (Am J Phys Anthropol 125 [2004] 42-50) for more terrestrial primates and rodents. This finding adds evidence to a model suggesting a functional link between arboreality-particularly locomotion on thin, flexible branches-and forelimb compliance. These data add another convergent trait between arboreal primates, Caluromys, and other arboreal marsupials and support the argument that all primates evolved from a common ancestor that was a fine-branch arborealist. [ABSTRACT FROM AUTHOR]

The article presents a study which examined the vertical activity of the yellow-necked mouse at the edge of a mixed forest. It was conducted in Central Bohemia, the Czech Republic, from 2003 to 2005. A total of 424 individuals were captured by the capture-mark-recapture (CMR) technique in live traps placed at ground level or in trees at heights of 1 and 2 meters. It noted that the yellow-necked mouse, Apodemus flavicollis, was the most commonly captured. It found that there was no clear seasonal variation in vertical activity during May to October and there was no significant difference between male and female vertical activity.

The responses of diurnal tree squirrels to logging were determined by comparing their abundance in recently logged forest, 20-25-yr-old logged forest, unlogged primary forest, a relatively disturbed secondary forest and a plantation in western Arunachal Pradesh. The squirrels recorded were the Himalayan striped squirrel (Tamiops macclellandi), hoary-bellied squirrel (Callosciurus pygerythrus), red-bellied squirrel (Callosciurus erythraeus) and the Malayan giant squirrel (Ratufa bicolor). The generalist hoary-bellied squirrel was the most common species overall. Its abundance was highest in logged forest and plantations that are characterized by low canopy cover and reduced tree density. It was the only species recorded in the plantations. The other three species were most abundant in unlogged forest. The abundance of the more arboreal Malayan giant squirrel and red-bellied squirrel was correlated to higher tree density and canopy cover, which are characteristic of unlogged primary forests. The reduced canopy cover, tree density and basal area in logged forest, and low tree species diversity and structural complexity in plantations lead to reduction or total absence of squirrels in these habitats. Degree of arboreality, diet and nesting requirements play an important role in squirrel abundance, with largersized or specialist species being more vulnerable to habitat modification due to logging. [ABSTRACT FROM AUTHOR]

Abstract: Although it is broadly accepted that small mammals often climb trees, only few studies explore arboreality in woodland rodents systematically. Here, we investigate the three-dimensional habitat use of wood mice Apodemus sylvaticus and bank voles Myodes glareolus at three different sites in Wytham Woods, Oxfordshire, under varying environmental conditions. A total of 12 trapping sessions was carried out between March and September 2003 and 2004. During each session, 100 Longworth live-traps with shrew escape holes were set in a 25-point-grid for 3 succeeding nights. Each time, 50 traps were placed on the ground, and 50 in surrounding trees at heights of 30–250cm. Wood mice were significantly more arboreal than bank voles, and male wood mice spent significantly more time in trees than did females. Arboreality in bank voles occurred only under high population densities and food shortage, and both species were significantly more arboreal in woodland with dense understorey. Thus we conclude that while arboreality is predominantly a result of inter- and intra-specific competition, of the two species we studied, only wood mice, being more agile, can afford to utilize trees without getting caught by predators, and that sex differences are due to male territoriality. Estimates of population sizes and distribution, as well as studies of inter-specific interactions and socio-spatial behaviour are presumed to be affected by these results, and are currently likely to underestimate rodent numbers considerably. [Copyright &y& Elsevier]

Diurnal refuge-site selection was studied in eleven free-ranging brown tree snakes (Boiga irregularis) in tropical forest on the island of Guam. These nocturnal and mostly arboreal snakes were tracked using implanted radio-transmitters. A vegetation survey of the study site was performed to determine if brown treesnakes non-randomly select certain plants for refuge-sites, and thermal profiles of representative refuge sites were obtained with Hobo data loggers. Brown treesnakes preferentially used Pandanus crowns for refuge-sites. Although Pandanus represents a small proportion (3.6%) of the forest, most snakes used Pandanus most of the time for refuge. The thermal characteristics of Pandanus were comparable to those of other refuge-sites. We speculate that features of Pandanus that provide basking opportunities and moist microhabitats may be important for brown treesnakes. As Pandanus is widely distributed throughout the natural range of the brown treesnake, this genus may represent an important refuge-site for this species. [ABSTRACT FROM AUTHOR]