Caluromys Philander Research Articles

Richness and distribution of New World marsupials (Didelphimorphia: Didelphidae) in the state of Piauí, Brazil

ABSTRACT Many gaps remain in understanding species evolution and distribution in Northeast Brazil, particularly in the Caatinga and Cerrado biomes. Our aims are to increase knowledge about the species of New World marsupials in the state of Piauí, identifying regions that are still poorly sampled, contributing to the delimitation of the geographic range of these species. We compiled online database data collection, scientific collection vouchers information and data from published articles. Twelve didelphid species were registred: Caluromys philander, Cryptonanus agricolai, Didelphis albiventris, Didelphis marsupialis, Gracilinanus agilis, Marmosa murina, Marmosa demerarae, Marmosops sp. Metachirus myosuros, Monodelphis domestica, Philander opossum, and Thylamys karimii. These represent about 18% of the Didelphidae occurring in Brazil. The survey revealed occurrences for 33 Piauí municipalities, representing only 12% of the state area. The extreme south and north of Piauí lack studies concerning marsupials, and parts of the centre-north and southeast are also poorly sampled. The results show an important geographic range increase for four species. Despite these results, Piauí is still an understudied region of the country. Valuable and immeasurable information may be lost due to degradation and loss of natural areas of Cerrado and Caatinga in the state.

Vestigial structures and variation in the evolution of the marsupial mammal dental development—a study of the woolly opossum Caluromys philander

The pattern of dental replacement in marsupial mammals has received much attention for its derived nature and potential relationship to the life history of the group. However, few species have been studied thoroughly, and little is known about the embryonic structures and their use in addressing issues of homology and dental evolution in general. We studied a developmental series of ten individuals of pouch young Caluromys philander to thoroughly document dental development with histological sections and 3D models of dental series. We report that the successor P3 arises from a lingual successional lamina from its predecessor dP3. The germs of vestigial, unerupted deciduous incisors and canines are present alongside their respective permanent successors. These discoveries demonstrate significant differences from the developmental patterns reported for Didelphis and Monodelphis and illustrate that an unsuspected diversity of dental ontogeny is not reflected in the adult pattern of mineralised, erupted or almost erupted teeth.

Rope bridges provide safe connectivity for the southern brown howler monkey (Alouatta guariba clamitans Cabrera, 1940) in an urban Atlantic Forest remnant

Abstract A southern brown howler monkey (Alouatta guariba clamitans) population occurs in a remnant of Atlantic Forest located inside an urban area of the municipality of São Paulo, Brazil. This population has been heavily anthropogenically impacted by collisions with vehicles, electrocutions on power lines, and falls onto roads. With the aim of reducing these impacts on howler monkeys, we installed four rope bridges in the forest canopy in Fontes do Ipiranga State Park (PEFI). We used mortality data collected within the PEFI to identify areas with high incident rates to place the bridges. The bridges were monitored continuously (24 hours per day) with camera traps for the 12 months following bridge installation (with one exception). The goal of this study was to evaluate the functionality of the bridges in road impact mitigation for the howler monkeys in the PEFI and for other arboreal species. We recorded use of three of the four rope bridges by five of the six arboreal mammal species known to occur in the PEFI with the following frequency: southern brown howler monkey – 60.5% of events, 70.8 events/month; orange-spined hairy dwarf porcupine – Coendou spinosus, 26.1% of events, 31 events/month; black-eared opossum – Didelphis aurita, 7.2% of events, 7.3 events/month, bare-tailed woolly opossum – Caluromys philander, 3.4% of events, 4.3 events/month and marmoset – Callithrix sp., 2.7% of events, 3.38 events/month. The time to first use of the bridges by howler monkeys in the two bridges for which there were data was 2 and 77 days, while other species took longer to habituate (113–344 days). Adult howler monkeys used all parts of the bridges to cross while younger howlers and the smaller species used mostly the longitudinal side lines. Given our findings of rope bridge use by five species in the PEFI, we recommend the installation of rope bridges of this design in other areas with similar species composition.

Diet of small mammals in semi‐deciduous forest fragments in Central Brazil

AbstractMarsupials and rodents are two of the most specious mammalian group, displaying a variety of diet and feeding habits. However, the knowledge about diet for several small mammal species is scant in the scientific literature, and most species are classified as insectivore–omnivore (marsupials), or frugivore–graminivore (rodents). In this study, we described diet composition based on digestive tract contents of 12 species of small mammals (7‐rodents and 5‐marsupials), in semi‐deciduous forest fragments of Central Brazil. We analysed 47 digestive tract contents belong to Calomys tener (10), Oecomys bicolor (10), Gracilinanus agilis (6), Marmosa murina (5), Rhipidomys macrurus (5), Calomys expulsus (2), Cryptonanus chacoensis (2), Monodelphis kunsi (2), Oecomys catherinae (2), Caluromys philander (1), Oligoryzomys mattogrossae (1) and Necromys lasiurus (1). We found parts of arthropods and fruits in the digestive tract of all species, with the exception of N. lasiurus, which contained only arthropods. The most representative arthropod taxa were Hymenoptera (present in 11 species), Coleoptera (9 spp.), Arachnida (7 spp.) and Isoptera (6 spp.). The seeds of Piperaceae (present in 3 small mammal species), Myrtaceae (2 spp.) and Poaceae (1 sp.) were also identified. This study reports the first records of diet composition for the marsupials C. chacoensis and M. murina, and rodents C. expulsus, C. tener, O. bicolor, O. catherinae and R. macrurus. Our findings contribute to understanding the diet composition and natural history of the Brazilian Savanna small mammals.

A New and Simple Method to Capture Small Arboreal Mammals: The Suspended Pitfall

The suspended pitfall demonstrates a new and simple mechanism to capture small arboreal and scansorial mammals. It is an arboreal version of the pitfalls traditionally used to capture terrestrial amphibians and reptiles. Buckets with bait inside are raised by a rope until they reach a tree branch at the desired height. Tests were performed in the Atlantic Forest at three different sites at the mouth of Doce River in Linhares, southeastern Brazil. In one of them suspended pitfalls were set up in the understory of a shaded cacao plantation (cabruca agroforest) in the branches of cacao trees between 2 and 3 m in height, and in the other they were placed in a native forest between 5 to 15 m in height. At the third site, suspended pitfalls were tested together with the other live traps used hitherto in the understory of other cabruca agroforest. The marsupials Didelphis aurita, Caluromys philander, Marmosa (Micoureus) paraguayana, Gracilinanus microtarsus, Marmosa murina and the rodent Rhipidomys mastacalis were captured by suspended pitfall. This live trap was capable of catching all sizes of small arboreal mammals, including juvenile individuals. This method proved to be functional for the capture of some small arboreal mammals and may be a complementary alternative for sampling in high forest strata.

Resting sites of opossums (Didelphimorphia, Didelphidae) in Atlantic Forest fragments

Abstract We report the type and pattern of use of resting sites used by 14 radio-tracked opossums. Philander frenatus rested in natural structures but also on spherical structures of dry leaves, probably built by them. Caluromys philander and Marmosa paraguayana rested at forest canopy preventing nest type identification. More than half of the resting site locations of each radio-tracked individual were in a single resting site. The repeated use of resting sites in the study area might be a strategy to stay close to resources and a protection against adverse weather conditions, predators and/or competitors.

Comparative ecogeographical variation in skull size and shape of two species of woolly opossums (genus Caluromys)

Environmental pressures are key mechanisms in the change of size or shape of an organism. In addition to external factors, the pressure of allometry (size-related shape changes) can also be present itself in the way that shape varies even in adulthood. In this study, we used a geometric morphometric approach to analyse skull size and shape variation in South-American Didelphidae, genus Caluromys, represented by two species, Caluromys philander and C. lanatus, in relation to allometry, geography and climate. We found significant allometric effects on these species, especially C. lanatus. The strong role of geographical space mainly on size of both species and on shape of C. lanatus suggests that they are spatially structured, supporting neutral processes, such as drift, in their evolution. Size of both species was related to latitudinal variation, the inverse pattern of Bergmann’s rule. Temperature and the set of bioclimatic variables influenced both size and shape of species. The shape of C. philander was influenced by bioclimatic variables (e.g. rainfall), while the shape of C. lanatus showed such influence (mostly temperature) but just when under the presence of allometry. Our results indicate the importance of allometry and environment in the patterns of skull shape variation in the South-American Caluromys, with a concomitant influence of geography. Climatic factors, such as the temperature, have strong influence on cranial changes along populations, with the two species varying similarly in skull size and shape along a climatic gradient. The latitudinal distribution, although mostly parapatric, of these congeneric species in South America should be in part responsible for their similarities in the observed phenotypic variation.

POSTURAL CLIMBING BEHAVIOUR OF DIDELPHID MARSUPIALS: PARALLELS WITH PRIMATES

Differences in body size and in the use of arboreal strata limit the climbing behaviour and performance of didelphids. Similarly to primates, the arboreal canopy dweller, Caluromys philander exhibits a diagonal-sequence gait. In contrast, terrestrial didelphids use a symmetrical lateral sequence in horizontal locomotion. Postural behaviour along thin supports may allow understanding the mechanisms behind the higher performance of arboreal didelphids climbing. Here in, we describe and compare gait sequence and postural behaviour of seven didelphids climbing a slender and flexible vertical support. Animals were stimulated to climb a vertical support of 1.25 cm diameter. Postural behaviour was qualitatively described for each species in the cycle of maximum velocity by a frame-by-frame analysis of gait cycles, evaluating (1) movements of the tail, (2) posture of hand and wrist when grasping, (3) distance of the body to the support, (4) lateral swinging of the body, (5) orientation of the head, (6) limb posture, and (7) stride cycle. Only arboreal species were capable of climbing with only two limbs grasping the support, keeping a straight body orientation at some distance from the support, and sustaining a more constant and regular climbing velocity. The tail played a role in didelphids with better climbing performance (i.e., higher relative velocity), counteracting the lateral swinging of the body, helping with the animal balance. However, the prehensile ability of the tail was not used in climbing. The most stunning result is that all didelphids grasped the rope between digits 2-3, a schizaxonic grasp, involving a neutral hand orientation regarding the ulna. The didelphids protracted the humerus at forelimb touchdown, and the angle between the arm and the horizontal body axis was greater than 90°. The same postures were already observed in horizontal locomotion of C. philander, Monodelphis domestica, and primates. Locomotory and postural adaptations for an arboreal lifestyle in didelphids seem to be limited to small to medium body sizes, up to the size of species of Caluromys. The arboreal locomotion of didelphids is an important key to understand adaptation and evolution of mammals to an arboreal niche, and the comparison with small primates may help to identify adaptive convergence to arboreal locomotion.

Incorporating habitat availability into systematic planning for restoration: a species‐specific approach for Atlantic Forest mammals

AbstractAimSpecies persistence often depends not only on habitat protection, but also on habitat restoration. The effectiveness of species conservation through habitat restoration can be enhanced by explicitly considering ‘habitat availability’, the combined effects of the total amount of habitat and its spatial configuration. We develop an approach for prioritizing land for restoration in a complex biome, considering habitat availability, land acquisition cost and biogeographical representation.LocationBrazilian Atlantic Forest.MethodsWe evaluate alternative restoration prioritization strategies for two mammal species with widely different dispersal abilities and habitat patch requirements. Our strategies focused on minimizing cost while meeting targets for biogeographical subregion representation and habitat availability metrics. We evaluated solutions based on the expected post‐restoration improvement in habitat availability per unit cost.ResultsRestoration through land acquisition to improve habitat availability for both species and to ensure 20% forest cover within each of the Atlantic Forest biogeographical subregions would cost US$ 17.5–20.5 billion. The 12.6 and 11.4 million ha of restored forest resulted in an increase of 10.5% and 9.8% in habitat area and 5518% (55‐fold) and 4100% (41‐fold) in future habitat availability forLeopardus pardalisandCaluromys philander, respectively. We found a high degree of concordance (> 75%) among selected planning units for each species.Main conclusionSubstantial improvements in habitat availability that benefit both species can be realized for minimal additional cost relative to solutions based solely on cost‐minimization and biogeographical subregion representation. We demonstrate that metrics based on metapopulation theory can be quantified in complex systems and used in a systematic restoration prioritization approach to improve habitat availability cost‐effectively. Concordance among priority areas for restoration for species with widely different dispersal abilities and habitat patch requirements supports the idea that many species in the Brazilian Atlantic Forest might benefit from plans based on indicator species. This is particularly useful in data‐deficient systems like the Brazilian Atlantic Forest.

Functional and evolutionary aspects of axial stability in euarchontans and other mammals

The presence of a stable thoracolumbar region, found in many arboreal mammals, is considered advantageous for bridging and cantilevering between discontinuous branches. However, no study has directly explored the link between osteological features cited as enhancing axial stability and the frequency of cantilevering and bridging behaviors in a terminal branch environment. To fill this gap, we collected metric data on costal and vertebral morphology of primate and nonprimate mammals known to cantilever and bridge frequently and those that do not. We also quantified the frequency and duration of cantilevering and bridging behaviors using experimental setups for species that have been reported to show differences in use of small branches and back anatomy (Caluromys philander, Loris tardigradus, Monodelphis domestica, and Cheirogaleus medius). Phylogenetically corrected principal component analysis reveals that taxa employing frequent bridging and cantilevering (C. philander and lorises) also exhibit reduced intervertebral and intercostal spaces, which can serve to increase thoracolumbar stability, when compared to closely related species (M. domestica and C. medius). We observed C. philander cantilevering and bridging significantly more often than M. domestica, which never cantilevered or crossed any arboreal gaps. Although no difference in the frequency of cantilevering was observed between L. tardigradus and C. medius, the duration of cantilevering bouts was significantly greater in L. tardigradus. These data suggest that osteological features promoting axial rigidity may be part of a morpho-behavioral complex that increases stability in mammals moving and foraging in a terminal branch environment.

Positional behaviour and tail use by the bare-tailed woolly opossum Caluromys philander (Didelphimorphia, Didelphidae)

We present the first quantitative description of postural behaviour of a free ranging metatherian, the bare-tailed woolly opossum, Caluromys philander. Postural behaviour was observed using 10 camera traps set in front of artificial nests, located in the understory of an Atlantic forest site in Rio de Janeiro, Brazil. Seven locomotory and positional modes were identified, with a predominance of diagonal couplets. Individuals used three types of grasp as observed in captivity, but the frequency of digital grasping was higher in the wild. The tail was used as an additional grasping limb, preventing falls and freeing hands to other activities, but the tail was also used to carry leaves for nest building. The use of camera traps may represent a breakthrough in the study of positional behaviours in the wild.

Cranial ontogeny ofCaluromys philander(Didelphidae: Caluromyinae): a qualitative and quantitative approach

The ontogeny of skull allometry has been the subject of research in didelphid, microbiotheriid, and dasyurid marsupials. We described and compared postweaning stages of cranial development in the woolly opossum Caluromys philander, a member of a distinct lineage of didelphids. We identified 31 qualitative morphological changes between juveniles and adults, many related to the trophic apparatus. Early development of the paracanine fossa in the snout, correlated with the presence of well-developed canines in juveniles, represents a remarkable difference between the ontogeny of C. philander and other marsupials. We performed bivariate and multivariate analyses of allometry on a data set composed of 14 cranial measurements and 45 specimens. Allometric scaling showed that braincase is relatively small in adulthood, whereas other neurocranial components, particularly the orbit, grew isometrically along its length. The palate becomes elongated by the combination of the isometry of its length and the negative allometry of its width. The rostrum lengthened, but its height remained proportionally constant. In relative terms the temporal fossa expanded inward following the marsupial model that combines the negative allometry of the braincase and the isometry of the zygomatic breadth. The mandible increased in robustness. The skull ontogeny of C. philander shares 4 allometric trends with 2 didelphids (Didelphis albiventris and Lutreolina crassicaudata) and two australidelphians (Dromiciops gliroides and Dasyurus albopunctatus). Three of these trends, breadth of palate, breadth of braincase, and height of occipital plate, were allometrically negative, whereas height of the dentary was positive. These common allometric trends may be interpreted as symplesiomorphic for marsupials, suggesting a high degree of conservatism in the skull development of Caluromys and other marsupials. DOI: 10.1644/09-MAMM-A-291.1.

Use of zygodactylous grasp by Caluromys philander (Didelphimorphia: Didelphidae)

The present report aims to quantify the use of zygodactylous (opposability of digits II to III) grasping in relation to positional modes and support size and orientation, in the highly arboreal, walking/climbing woolly opossum, Caluromys philander. For this purpose, four captive adult C. philander were intensively video-recorded and their positional behavior, hand grasp, and support size and orientation use were analyzed frame-by-frame. Overall, C. philander used a zygodactylous grasp in 81.3±1.2% of bouts. In terms of support features, this grasp was particularly common on (a) supports that could be wholly and partly held by the animals’ hand and (b) vertical supports in particular. In a comparable manner, zygodactyly dominated during above-support positional modes, but was significantly less used during bridging and suspension. The results show that zygodactyly provided an above-support secure and steady grasp on relatively unstable arboreal supports, by aligning the hand with the main axis of the support. This very likely assisted in controlling over the applied torques during cautious quadrupedal and climbing activities with extended hand contact that characterizes the locomotor strategy of C. philander. These observations need to be further tested by more detailed kinetic studies and on a larger sample of arboreal didelphids.

Brief communication: Forelimb compliance in arboreal and terrestrial opossums

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 Monodelphis 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. Monodelphis 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.

Isolation, characterization and cross-species amplification of new microsatellite markers for three opossum species of the Didelphidae family

The American opossums from the Didelphidae family (Order: Didelphimorphia) are on the IUCN Red List, and their threatened status varies from extinct to data deficient. Although microsatellites have already been developed for some species, only a small amount of population genetic analysis of the didelphid wild populations has been made using them. In this work, we developed new microsatellites and tested for cross-species amplification for one species from the subfamily Caluromyinae, Caluromys philander, and two from the subfamily Didelphinae, Didelphis aurita and Metachirus nudicaudatus, to determine the degree of gene flow and isolation of populations of those species in some fragments of the Atlantic Forest in Minas Gerais state, Brazil. Among all microsatellite loci amplified, 18 from C. philander, 9 from D. aurita, and 17 from M. nudicaudatus were polymorphic. Cross-species amplification of these polymorphic microsatellite loci were performed in these three species and in one additional related species Micoureus paraguayanus. Our data showed that microsatellites were not highly conserved among Didelphidae species.

História natural e biologia reprodutiva de marsupiais no Pantanal, Mato Grosso, Brasil

Three forested habitats at Pantanal of Pocone (Mato Grosso) were sampled during 17 months, with an effort of 38,635 trap-nights, resulting in a 6.3% of trapping success. Six marsupial and eight rodent species were recorded. Natural history, reproductive biology, behavior and habitat use are described for six marsupial species from the Pantanal floodplain: Caluromys philander (Linnaeus, 1758), Didelphis albiventris Lund, 1840, Gracilinanus agilis (Burmeister, 1854), Micoureus demerarae (Thomas, 1905), Monodelphis domestica (Wagner, 1842) and Philander opossum (Linnaeus, 1758). Micoureus demerarae was the species with the highest number of captured individuals (n = 240) and with the highest number of capture events (n = 1287). Reproduction of most species begins at the end of the dry season, being intensified during the wet season. The flooded forest locally known as 'landis' showed the highest marsupial species richness (six species), whereas the forests that are never flooded, locally known as 'cordilheiras', and the seasonally flooded forest, locally known as 'cambarazais', showed the lowest species richness, with three species each.

Allometric, Phylogenetic, and Adaptive Components of Climbing Performance in Seven Species of Didelphid Marsupials

Didelphid marsupials specialized in arboreal locomotion have morphological features convergent with primates, and hence are an ideal group to test hypotheses about the evolution of arboreality. We analyzed the relative contributions of allometric, phylogenetic, and adaptive aspects to the climbing performance of 7 species of didelphid marsupials of the Atlantic Forest of Brazil. These species encompass a diversity of body sizes, use of the vertical strata, and lineages within didelphid marsupials. Climbing performance was evaluated by measuring the velocity in climbing 3 nylon ropes of 0.6, 0.9, and 1.25 cm diameter. The cycle of maximum velocity was chosen to measure relative stride length, frequency, and relative velocity. As expected, arboreal species (Gracilinanus microtarsus, Marmosops incanus, Micoureus paraguayanus, and Caluromys philander) had higher relative climbing velocities than more terrestrial species (Didelphis aurita, Philander frenatus, and Metachirus nudicaudatus). Stride frequency was mostly associated with phylogeny and vertical use of the forest, but relative velocities generally were determined by a combination of stride length and frequency. Differences in climbing performance originated early in the diversification of the group, but continued to evolve because significant differences also were detected at the subfamily, tribe, and genus levels, which seems to parallel the evolution of grasping abilities in primates.

Arboreal walking performance in seven didelphid marsupials as an aspect of their fundamental niche

Abstract Species of didelphid marsupials (Didelphimorphia, Didelphidae) differ in their use of the forest strata, but it is not clear whether these differences are in fundamental or realized niches. The fundamental niche of seven species of didelphids (Caluromys philander,Didelphis aurita,Gracilinanus microtarsus,Marmosops incanus,Metachirus nudicaudatus,Micoureus demerarae, andPhilander frenatus) was compared using their performance in arboreal walking. The association between performance and vertical use of the forest also was tested accounting for phylogenetic and allometric effects. Tests consisted of making the animal cross five 3 m long horizontal supports of different diameters, 1 m from the ground. The cycle of maximum speed was chosen to measure stride length, frequency and velocity. Arboreal species performed better than the terrestrial ones, but a major part of the variation in stride length (70.95%) and stride frequency (88.10%) was associated with body size. Part of the variation in stride length independent of body size (14.05%) was associated with the degree of vertical use of the forest, after phylogenetic effects were accounted for. Fundamental niches of six of the seven species were discriminated with the performance tests used. Discrepancies between the realized and fundamental niches can be inferred for two of these species,D. auritaandP. frenatus.

Food habits of sympatric opossums coexisting in small Atlantic Forest fragments in Brazil

The diets of sympatric species of opossums coexisting in small (<10 ha) Atlantic Forest fragments were studied at Poço das Antas Biological Reserve, southeastern Brazil. Food items consumed by Caluromys philander and Didelphis aurita were investigated through the analysis of faecal contents, and compared with the diet of Micoureus demerarae analysed in a previous study. The major diet components for all three species were arthropods and fruits, with a high richness of items of both feeding categories; feathers were also found in the diet of D. aurita. The most frequent insect orders overall were Hymenoptera and Coleoptera, and most seeds were from plants of secondary vegetation such as Cecropia and Piper. The diets showed little variation along time and space for all three species. Diets were also similar among species, except for a larger consumption of Arachnida and Diplopoda and a smaller consumption of Lepidoptera by D. aurita when compared to M. demerarae. Diversity of food items was lower for C. philander when compared with either other species. There was a high feeding niche overlap between species, suggesting that differentiation in diet composition would not be enough to allow coexistence of the three species in small fragments. Coexistence may rather be allowed by vertical segregation and/or by differences in prey size.

Locomotor mechanics of the slender loris ( Loris tardigradus)

The quadrupedal walking gaits of most primates can be distinguished from those of most other mammals by the presence of diagonal-sequence (DS) footfall patterns and higher peak vertical forces on the hindlimbs compared to the forelimbs. The walking gait of the woolly opossum ( Caluromys philander), a highly arboreal marsupial, is also characterized by diagonal-sequence footfalls and relatively low peak forelimb forces. Among primates, three species— Callithrix, Nycticebus, and Loris—have been reported to frequently use lateral-sequence (LS) gaits and experience relatively higher peak vertical forces on the forelimbs. These patterns among primates and other mammals suggest a strong association between footfall patterns and force distribution on the limbs. However, current data for lorises are limited and the frequency of DS vs. LS walking gaits in Loris is still ambiguous. To test the hypothesis that patterns of footfalls and force distribution on the limbs are functionally linked, kinematic and kinetic data were collected simultaneously for three adult slender lorises ( Loris tardigradus) walking on a 1.25 cm horizontal pole. All subjects in this study consistently used diagonal-sequence walking gaits and always had higher peak vertical forces on their forelimbs relative to their hindlimbs. These results call into question the hypothesis that a functional link exists between the presence of diagonal-sequence walking gaits and relatively higher peak vertical forces on the hindlimbs. In addition, this study tested models that explain patterns of force distribution based on limb protraction angle or limb compliance. None of the Loris subjects examined showed kinematic patterns that would support current models proposing that weight distribution can be adjusted by actively shifting weight posteriorly or by changing limb stiffness. These data reveal the complexity of adaptations to arboreal locomotion in primates and indicate that diagonal-sequence walking gaits and relatively low forelimb forces could have evolved independently.