Laboratory investigations have provided important insight into the functional underpinnings of primate locomotor performance; however, it is unclear to what extent gait patterns in the laboratory reflect those of primates moving in natural settings. We filmed quadrupedal loco-motor activity in eight platyrrhine species at the Tiputini Biodiversity Station, Ecuador, and three additional platyrrhine species at La Suerte Biological Field Station, Costa Rica, and also quantified the diameter and orientation of locomotor substrates using remote sensors (N = 1,233 strides). We compared overall arboreal quadrupedal gait kinematic patterns in free-ranging individuals to those of laboratory platyrrhine congenerics. As expected, gait kinematics of free-ranging individuals were more variable than laboratory counterparts. Within the free-ranging dataset, Ateles and Alouatta increased limb phase on inclines (p=0.04; p=0.002, respectively), Lagothrix increased duty factors on inclines (p=0.002), Cebus increased duty factors on declines (p=0.02), and both Saimiri and Saguinus displayed an inverse relationship between limb phase and substrate diameter (p=0.05; p=0.03, respectively). This study confirms the preference for diagonal sequence gaits in free-ranging primates (i.e., 87.9% of all recorded symmetrical strides) and that in both settings primates tend to adjust gait patterns to promote security through longer contact times on non-horizontal substrates and increased limb phase on inclined substrates. We show that laboratory and field investigations of primate locomotion yield consistent patterns but that field studies can capture additional aspects of gait variability and flexibility in response to the increased substrate complexity of natural environments.
more »
« less
Symposia and Oral Abstracts
Primates' near exclusive use of diagonal sequence gaits has been
hypothesized to enhance stability on arboreal substrates. To assess
how primate gait kinematics vary in complex arboreal environments,
we filmed eight species of free-ranging primates (Ateles, Lagothrix,
Alouatta, Pithecia, Callicebus, Saimiri, Saguinus, and Cebuella) at
the Tiputini Biodiversity Station, Ecuador, and quantified the
diameter and orientation of locomotor substrates using remote
sensors (n = 858 strides). Five of the species used primarily diagonal
sequence, diagonal couplet (DSDC) gaits. Callicebus frequently used
lateral sequence gaits (i.e., ~50% of strides). Saguinus and Cebuella
most frequently used asymmetrical gaits. We examined the effects of
substrate diameter and orientation on duty factor and interlimb
phasing, controlling for speed via ANCOVA. Ateles increased limb
phase on inclines (p=0.04), Lagothrix had greater duty factors on
inclines (p=0.002), Callicebus exhibited greater duty factors (p=0.04)
and lower limb phase values on declines (p=0.001), and both Saimiri
and Saguinus displayed an inverse relationship between limb phase
and substrate diameter (p=0.05, p=0.03, respectively). This study
confirms the ubiquity of diagonal sequence gaits in free-ranging
primates and at least partially supports predicted biomechanical
adjustments to promote stability including: increased duty factor on
nonhorizontal substrates, increased limb phase on inclines, and
decreased limb phase on declines. Other species-specific kinematic
adjustments to substrate variation are likely related to body size and
ecological variation but require further investigation.
more »
« less
- Award ID(s):
- 1640552
- NSF-PAR ID:
- 10167059
- Date Published:
- Journal Name:
- Integrative and Comparative Biology
- Volume:
- 59
- Issue:
- Supplement_1
- ISSN:
- 1540-7063
- Page Range / eLocation ID:
- e59
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
more » « less
Abstract Objectives Primate diagonal sequence (DS) gaits are often argued to be an adaptation for moving and foraging in the fine‐branch niche; however, existing data have come predominantly from laboratory studies that are limited in taxonomic breadth and fail to account for the structural and ecological variation of natural substrates. We test the extent to which substrate diameter and orientation influence gait sequence type and limb phase in free‐ranging primates, as well as how phylogenetic relatedness might condition response patterns.
Materials and methods We filmed quadrupedal locomotion in 11 platyrrhine species at field sites in Ecuador and Costa Rica and measured the diameter and orientation of locomotor substrates using remote sensors. We quantified limb phase values and classified strides by gait sequence type (
N = 988 strides).Results Our results show that most of the species in our sample consistently used DS gaits, regardless of substrate diameter or orientation; however, all taxa also used asymmetrical and/or lateral sequence gaits. By incorporating phylogenetic eigenvectors into our models, we found significant differences in gait sequence patterns and limb phase values among the major platyrrhine clades, suggesting that phylogeny may be a better predictor of gait than substrate diameter or orientation.
Discussion Our field data generally corroborate locomotor patterns from laboratory studies but capture additional aspects of gait variability and flexibility in response to the complexity of natural environments. Overall, our results suggest that DS gaits are not exclusively tailored to narrow or oblique substrates but are used on arboreal substrates in general.
-
more » « less
Abstract Wild primates encounter complex matrices of substrates that differ in size, orientation, height, and compliance, and often move on multiple, discontinuous substrates within a single bout of locomotion. Our current understanding of primate gait is limited by artificial laboratory settings in which primate quadrupedal gait has primarily been studied. This study analyzes wild
Saimiri sciureus (common squirrel monkey) gait on discontinuous substrates to capture the realistic effects of the complex arboreal habitat on walking kinematics. We collected high‐speed video footage at Tiputini Biodiversity Station, Ecuador between August and October 2017. Overall, the squirrel monkeys used more asymmetrical walking gaits than symmetrical gaits, and specifically asymmetrical lateral sequence walking gaits when moving across discontinuous substrates. When individuals used symmetrical gaits, they used diagonal sequence gaits more than lateral sequence gaits. In addition, individuals were more likely to change their footfall sequence during strides on discontinuous substrates. Squirrel monkeys increased the time lag between touchdowns both of ipsilaterally paired limbs (pair lag) and of the paired forelimbs (forelimb lag) when walking across discontinuous substrates compared to continuous substrates. Results indicate that gait flexibility and the ability to alter footfall patterns during quadrupedal walking may be critical for primates to safely move in their complex arboreal habitats. Notably, wild squirrel monkey quadrupedalism is diverse and flexible with high proportions of asymmetrical walking. Studying kinematics in the wild is critical for understanding the complexity of primate quadrupedalism. -
more » « less
Abstract Objectives Documenting the variety of quadrupedal walking gaits in a variety of marsupials (arboreal vs. terrestrial, with and without grasping hind feet), to aid in developing and refining a general theory of gait evolution in primates.
Materials and Methods Video records of koalas, ringtail possums, tree kangaroos, sugar gliders, squirrel gliders, wombats, numbats, quolls, a thylacine, and an opossum walking on a variety of substrates were made and analyzed to derive duty factors and diagonalities for symmetrical walking gaits. The resulting distributions of data points were compared with published data and theories.
Results Terrestrial marsupials' gaits overwhelmingly plot slightly below the theoretical “horse line” (Cartmill et al., Zoological Journal of the Linnean Society. 2002;136:401–420) typical of terrestrial mammals; arboreal marsupials' gaits overwhelmingly plot more decisively above it. Both distributions are roughly parallel to the horse line, but arboreal animals exhibit increased diagonality, so that their higher‐speed walking gaits overlap with those of typical primates on the Hildebrand diagram of diagonality against duty factor.
Conclusions Quadrupeds avoid gaits lying exactly on the (theoretically optimum) horse line, to avoid fore/hind limb interference (“forging”). This can be accomplished by either a slight reduction in diagonality (“downshifting”) or a more decisive increase (“upshifting”). Tree‐dwellers adopt the second option to eliminate unilateral bipods of support from the gait cycle. The upshifted horse line represents an early phase in the evolution of primate‐like diagonal‐sequence gaits.
-
more » « less
Abstract The grasping capabilities and gait kinematics characteristic of primates are often argued to be adaptations for safely moving on small terminal branches. The goal of this study was to identify whether Eastern gray squirrels (
Sciurus carolinensis )—arboreal rodents that frequently move and forage on small branches, lack primate‐like grasping and gait patterns, and arguably represent extant analogs of a stem primate ancestor—adjust gait kinematics to narrow and nonhorizontal branches. We studied locomotor kinematics of free‐ranging and laboratory‐housed squirrels moving over various substrates. We used high‐speed video to film (a) a population of free‐ranging squirrels moving on natural substrates and (b) laboratory‐housed squirrels moving on horizontal poles. Substrates were coded as small, medium, or large relative to squirrel trunk diameter, and as inclined, declined, or horizontal. Free‐ranging squirrels used more gallops and half‐bounds on small‐ and medium‐sized substrates, and more high‐impact bounds, with reduced limb‐lead durations, on declined substrates. Laboratory squirrels moved at higher speeds than free‐ranging squirrels and responded to decreasing diameter by using more gallops and half‐bounds, lowering speed, and—controlling for speed—increasing mean duty factor, mean number of supporting limbs, and relative forelimb lead duration. Our inability to detect substantial diameter or orientation‐related gait adjustments in the wild may be due to a limited accounting of confounding influences (e.g., substrate compliance). Ultimately, studies assessing stability measures (e.g., center of mass fluctuations and peak vertical force) are required to assess whether primates' enhanced grasping and gait patterns engender performance advantages on narrow or oblique substrates.
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1093/icb/icz003
