Meeting Abstract

P2-152   -   The parrot’s beak supports and propels tripedal locomotion Young, MW*; Dickinson, E; Fischer, HM; Hanna, CS; Currier, A; Davoli, EC; Flaim, ND; Granatosky, MC; College of Osteopathic Medicine, New York Institute of Technology, Old Westbury, NY; College of Osteopathic Medicine, New York Institute of Technology, Old Westbury, NY; College of Osteopathic Medicine, New York Institute of Technology, Old Westbury, NY; College of Osteopathic Medicine, New York Institute of Technology, Old Westbury, NY; College of Osteopathic Medicine, New York Institute of Technology, Old Westbury, NY; College of Osteopathic Medicine, New York Institute of Technology, Old Westbury, NY; College of Osteopathic Medicine, New York Institute of Technology, Old Westbury, NY; College of Osteopathic Medicine, New York Institute of Technology, Old Westbury, NY myoung08@nyit.edu https://www.nyit.edu/bio/Michael.Granatosky

Three-legged animals do not exist today, and no such animal is found in the fossil record. Arguably, this “forbidden” phenotype is attributable to an early genetic adoption of a bilaterally symmetrical body plan occurring before the advent of limbs. However, tripedalism is employed by a few animals; none so well-cited as the Psittaciformes that employ their beaks as a third limb during vertical climbing. To determine the beak’s role in this tripedal gait, we measured the external forces the beak exerts on the substrate. We collected these data from six rosy-faced lovebirds (Agapornis roseicollis) during vertical climbing and compared these forces to the hindlimb forces on the same substrate and during bipedal terrestrial walking. Consistent with other bipedal birds, the hindlimb of rosy-faced lovebirds supports ~120% of body weight (%bw) and demonstrates net neutral braking and propulsive forces. During vertical climbing, the beak (~54 %bw) and hindlimbs (~72 %bw) serve a propulsive role. Further, the hindlimbs tend to support tensile (~37 %bw) and compressive (~22 %bw) loads depending on whether they are the leading or lagging limbs. The beak always serves a tensile pulling function (~38%BW). Propulsive and tensile forces exerted by the beak are consistent with what has been reported in the forelimb of vertical climbing mammals. Psittaciformes use their beak and neck musculature to support and propel their tripedal gait like a leg. The tripedal gaits of parrots represent an anatomical and neuromuscular novelty breaking from the normal pattern of tetrapod left/right limb asynchrony.