Hand and body position during locomotor behavior in the aye‐aye ( Daubentonia madagascariensis )

135

Effects of substrate diameter on locomotor biodynamics were studied in the gray short-tailed opossum (Monodelphis domestica). Two horizontal substrates were used: a flat 'terrestrial' trackway with a force platform integrated into the surface and a cylindrical 'arboreal' trackway (20.3·mm diameter) with a force-transducer instrumented region. On both terrestrial and arboreal substrates, fore limbs exhibited higher vertical impulse and peak vertical force than hind limbs. Although vertical limb impulses were lower on the terrestrial substrate than on the arboreal support, this was probably due to speed effects because the opossums refused to move as quickly on the arboreal trackway. Vertical impulse decreased significantly faster with speed on the arboreal substrate because most of these trials were relatively slow, and stance duration decreased with speed more rapidly at these lower speeds. While braking and propulsive roles were more segregated between limbs on the terrestrial trackway, fore limbs were dominant both in braking and in propulsion on the arboreal trackway. Both fore and hind limbs exerted equivalently strong, medially directed limb forces on the arboreal trackway and laterally directed limb forces on the terrestrial trackway. We propose that the modifications in substrate reaction force on the arboreal trackway are due to the differential placement of the limbs about the dorsolateral aspect of the branch. Specifically, the pes typically made contact with the branch lower and more laterally than the manus, which may explain the significantly lower required coefficient of friction in the fore limbs relative to the hind limbs.

Section: Behavioral Adaptations For Arboreal Locomotionmentioning

confidence: 99%

The biodynamics of arboreal locomotion: the effects of substrate diameter on locomotor kinetics in the gray short-tailed opossum (Monodelphis domestica)

Lammers

Biknevicius

2004

135

“…Aye-ayes, which are able to grasp branches of 80mm in diameter, switch from a 'full-curl' hand position during locomotion on a horizontal branch to a 'full-grip' hand position on slightly ascending branches (30-35deg) (Krakauer et al, 2002). This may be due to the need to generate tensile forces as they move upwards.…”

Section: Kinematic Changes On Inclined Branchesmentioning

confidence: 99%

“…Nakano suggested that this shift in the touch-down position of the forelimbs depends on substrate inclination in each species, which gives rise to the assumption of a significant correlation between limb proportion, inclination and the position of the center of mass (Nakano, 2002). Yet, between 0 and 30deg substrate orientation, forelimbs and hindlimbs in the gray short-tailed opossum are placed in a comparable way (Lammers et al, 2004;Lammers, 2007), and an unmodified body position was also observed in the aye-aye (Krakauer et al, 2002). The influence of limb proportions on locomotor performance is supported by observations regarding differences in limb flexion; elbow and knee joints, for example, are consistently more flexed at touch-down and midstance on sloped branches in primates that possess long limbs (lemurids and lorisids) than in cheirogaleids, which possess short limbs (Stevens, 2003).…”

Section: Introductionmentioning

confidence: 99%

“…The need to increase stability on inclined branches also results in differences in limb placement. The aye-aye, for example, uses primarily 'full grip' rather than 'full curl' or 'digit-2-curl' hand postures during locomotion on shallow inclines (Krakauer et al, 2002). The forelimbs of the white-handed gibbon and the Japanese macaque are placed underneath the branch whereas the hindlimbs make contact with the top, in order to permit maximum propulsion (Nakano, 2002).…”

Section: Introductionmentioning

confidence: 99%

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The kinematic consequences of locomotion on sloped arboreal substrates in a generalized (Rattus norvegicus) and a specialized (Sciurus vulgaris) rodent

Schmidt

Fischer

2011

SUMMARY Small mammals must negotiate terrains that consist of numerous substrates that vary in diameter, surface structure, rigidity and orientation. Most studies on mammals have focused on the effects of substrate diameter during horizontal locomotion, especially in small- to medium-sized primates and marsupials. Locomotion across sloped arboreal substrates, however, is poorly understood. Here, in order to determine which locomotor parameters a terrestrial mammal, the rat, and a tree-dwelling mammal, the European red squirrel, modify in response to differences in substrate orientation, three-dimensional kinematics were examined using biplanar videoradiography as the animals moved on 30 and 60 deg inclined branches. Our results revealed that to maintain stability and friction as well as balance during inclined branch locomotion, these species utilize comparable locomotor adjustments despite significant differences in travel speed and gait. Rats and European red squirrels increased limb flexion and retraction in order to bring the center of mass as close as possible to the substrate surface and to achieve maximum propulsion. Additionally, forelimbs were placed more laterally and underneath the branch whereas the hindlimbs were placed approximately on the top of the branch. These locomotor adjustments, which have also been observed in primates and marsupials, are independent of speed, morphological adaptations and limb proportions and thus might be strategies used by early mammals. Our results also suggest that mammals that lack, or have reduced, grasping abilities try to maintain the locomotor mode used during horizontal branch locomotion on inclined branches for as long as possible.

“…Behavioral studies suggest that aye-ayes curl their fingers off the substrate during horizontal and descending locomotion, placing the entire forelimb load on the palm (Oxnard et al, 1990). However, in a study of arboreal locomotion, Krakauer et al (Krakauer et al, 2002) showed that aye-ayes do not always curl all fingers off the substrate. Instead, they found that the animals in their study used a variety of different hand postures, including postures in which the digits make direct contact with the substrate.…”

Section: Introductionmentioning

confidence: 99%

Hand and foot pressures in the aye-aye (Daubentonia madagascariensis) reveal novel biomechanical trade-offs required for walking on gracile digits

Kivell

Schmitt

Wunderlich

2010

Self Cite

SUMMARYArboreal animals with prehensile hands must balance the complex demands of bone strength, grasping and manipulation. An informative example of this problem is that of the aye-aye (Daubentonia madagascariensis), a rare lemuriform primate that is unusual in having exceptionally long, gracile fingers specialized for foraging. In addition, they are among the largest primates to engage in head-first descent on arboreal supports, a posture that should increase loads on their gracile digits. We test the hypothesis that aye-ayes will reduce pressure on their digits during locomotion by curling their fingers off the substrate. This hypothesis was tested using simultaneous videographic and pressure analysis of the hand, foot and digits for five adult aye-ayes during horizontal locomotion and during ascent and descent on a 30° instrumented runway. Aye-ayes consistently curled their fingers during locomotion on all slopes. When the digits were in contact with the substrate, pressures were negligible and significantly less than those experienced by the palm or pedal digits. In addition, aye-ayes lifted their hands vertically off the substrate instead of 'toeing-off' and descended head-first at significantly slower speeds than on other slopes. Pressure on the hand increased during head-first descent relative to horizontal locomotion but not as much as the pressure increased on the foot during ascent. This distribution of pressure suggests that aye-ayes shift their weight posteriorly during head-first descent to reduce loads on their gracile fingers. This research demonstrates several novel biomechanical trade-offs to deal with complex functional demands on the mammalian skeleton. Supplementary material available online at