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ABSTRACT Jumping is a crucial behavior in fitness-critical activities including locomotion, resource acquisition, courtship displays and predator avoidance. In primates, paleontological evidence suggests selection for enhanced jumping ability during their early evolution. However, our interpretation of the fossil record remains limited, as no studies have explicitly linked levels of jumping performance with interspecific skeletal variation. We used force platform analyses to generate biomechanical data on maximal jumping performance in three genera of callitrichine monkeys falling along a continuum of jumping propensity: Callimico (relatively high propensity jumper), Saguinus (intermediate jumping propensity) and Callithrix (relatively low propensity jumper). Individuals performed vertical jumps to perches of increasing height within a custom-built tower. We coupled performance data with high-resolution micro-CT data quantifying bony features thought to reflect jumping ability. Levels of maximal performance between species – e.g. maximal take-off velocity of the center of mass (CoM) – parallel established gradients of jumping propensity. Both biomechanical analysis of jumping performance determinants (e.g. CoM displacement, maximal force production and peak mechanical power during push-off) and multivariate analyses of bony hindlimb morphology highlight different mechanical strategies among taxa. For instance, Callimico, which has relatively long hindlimbs, followed a strategy of fully extending of the limbs to maximize CoM displacement – rather than force production – during push-off. In contrast, relatively shorter-limbed Callithrix depended mostly on relatively high push-off forces. Overall, these results suggest that leaping performance is at least partially associated with correlated anatomical and behavioral adaptations, suggesting the possibility of improving inferences about performance in the fossil record. 

Abstract Several studies comparing primate locomotion under lab versus field conditions have shown the importance of implementing both types of studies, as each has their advantages and disadvantages. However, three‐dimensional (3D) motion capture of primates has been challenging under natural conditions. In this study, we provide a detailed protocol on how to collect 3D biomechanical data on primate leaping in their natural habitat that can be widely implemented. To record primate locomotion in the dense forest we use modified GoPro Hero Black cameras with zoom lenses that can easily be carried around and set up on tripods. We outline details on how to obtain camera calibrations at greater heights and how to process the collected data using the MATLAB camera calibration app and the motion tracking software DLTdv8a. We further developed a new MATLAB application “WildLeap3D” to generate biomechanical performance metrics from the derivedx,y,zcoordinates of the leaps. We provide details on how to collect data on support diameter, compliance, and orientation, and combine these with the jumps to study locomotor performance in an ecological context. We successfully reconstructed leaps of wild primates in the 3D space under natural conditions and provided data on four representative leaps. We provide exemplar data on primate velocity and acceleration during a leap and show how our protocol can be used to analyze segmental kinematics. This study will help to make motion capture of freely moving animals more accessible and help further our knowledge about animal locomotion and movement. 

Abstract ObjectivesDespite qualitative observations of wild primates pumping branches before leaping across gaps in the canopy, most studies have suggested that support compliance increases the energetic cost of arboreal leaping, thus limiting leaping performance. In this study, we quantified branch pumping behavior and tree swaying in wild primates to test the hypothesis that these behaviors improve leaping performance. Materials and MethodsWe recorded wild colobine monkeys crossing gaps in the canopy and quantitatively tracked the kinematics of both the monkey and the compliant support during behavioral sequences. We also empirically measured the compliance of a sample of locomotor supports in the monkeys' natural habitat, allowing us to quantify the resonant properties of substrates used during leaping. ResultsAnalyses of three recordings show that adult red colobus monkeys (Piliocolobus tephrosceles) use branch compliance to their advantage by actively pumping branches before leaping, augmenting their vertical velocity at take‐off. Quantitative modeling of branch resonance periods, based on empirical measurements of support compliance, suggests that monkeys specifically employed branch pumping on relatively thin branches with protracted periods of oscillation. Finally, an additional four recordings show that both red colobus and black and white colobus monkeys (Colobus guereza) utilize tree swaying to cross large gaps, augmenting horizontal velocity at take‐off. DiscussionThis deliberate branch manipulation to produce a mechanical effect for stronger propulsion is consistent with the framework of instrumental problem‐solving. To our knowledge, this is the first study of wild primates which quantitatively shows how compliant branches can be used advantageously to augment locomotor performance. 

Abstract ObjectivesAn accident during arboreal locomotion can lead to risky falls, but it remains unclear that the extent to which primates, as adept arborealists, change their locomotion in response to the perceived risk of moving on high supports in the tree canopy. By using more stable forms of locomotion on higher substrates, primates might avoid potentially fatal consequences. Materials and MethodsUsing high‐speed cameras, we recorded the quadrupedal locomotion of four wild lemur species—Eulemur rubriventer,Eulemur rufifrons, Hapalemur aureus, and Lemur catta(N = 113 total strides). We quantified the height, diameter, and angular orientation of locomotor supports using remote sensors and tested the influence of support parameters on gait kinematics, specifically predicting that in response to increasing substrate height, lemurs would decrease speed and stride frequency, but increase stride length and the mean number of supporting limbs. ResultsLemurs did not adjust stride frequency on substrates of varying height. Adjustments to speed, stride length, and the mean number of supporting limbs in response to varying height often ran counter to predictions. OnlyE. rubriventerdecreased speed and increased the mean number of supporting limbs on higher substrates. DiscussionResults suggest that quadrupedal walking is a relatively safe form of locomotion for lemurs, requiring subtle changes in gait to increase stability on higher—that is, potentially riskier—substrates. Continued investigation of the impact of height on locomotion will be important to determine how animals assess risk in their environment and how they choose to use this information to move more safely.