P3.65 Tuesday, Jan. 6 Aye-aye hand posture and loading of their specialised digits during quadrupedal locomotion KIVELL, TL*; KRAMER, EM; WUNDERLICH, RE; Duke University; Duke University; James Madison University firstname.lastname@example.org
Primate hands are often subject to heavy loads during quadrupedal locomotion. Primates using gaits or substrates in which these loads are particularly high will typically either (1) possess morphology that ameliorates potentially high loads (e.g., shorter, more robust digits in terrestrial cercopithecoids) or (2) use behavioral modifications to prevent high loads (e.g., knuckle-walking or fist-walking in great apes). Aye-ayes (Daubentonia madagascariensis) are unique in having exceptionally long, slender fingers specialized for foraging yet the frequency with which they engage in head-first descent is predicted to increase loads on their hands. Little is known about how aye-ayes cope with this seemingly contradictory morphology and locomotion. Behavioral studies suggest that aye-ayes curl their fingers during horizontal and declined locomotion, placing all of the forelimb load on the palm (Oxnard et al., 1990) but other research has shown that this is not always the case (Krakauer et al., 2002). We investigated hand and digit load in aye-ayes during horizontal, ascending and descending quadrupedal locomotion. Four aye-ayes walked along a horizontal and inclined (30) flat substrate with an EMED-ST pressure mat imbedded within the substrate. Kinematic data were collected by videotaping from the lateral view. Forelimb force and pressure increased during head-first decent and decreased during ascent relative to horizontal locomotion. Aye-ayes rarely load their digits on any substrate, especially during head-first descent. Our results show that aye-ayes have modified their behavior by freeing their digits from forelimb loads, especially when descending inclined substrates, to accommodate their highly specialized hand morphology.