Biomechanical analysis of the distal hindlimb of raptorial birds (Accipitridae, Falconidae and Pandionidae): force and velocity in equilibrium

MOSTO, M.C.; DEGRANGE, F.J.

Conferencia; I Worldwide Raptor Conference; 2013

To establish the commitment of the tarsometatarsus and foot with their capture technique, the velocity ratio (Vr) was calculated for 26 taxa from the raptorial families Falconidae,Accipitridae and Pandionidae. Furthermore, the resultant force of the muscles involved in flexing the digits was estimated through its physiological cross sectional area (PCSA) for four species. Regarding the tarsometatarsus, the Accipitrinae and Polyborinae exhibit the highest values of Vr whereas in Herpetotheres cachinnans, Falco peregrinus and Pandion haliaetus this ratio is lower, indicating a higher commitment with force. In general, digits I and III present the highest Vr (higher commitment with the speed) and digits II and IV show lower rates (higher commitment with force). The digit I of Caracara plancus, Spiziapteryx circumcincta and some Buteoninae (Buteo erythonotus, Buteogallus urubitinga and Geranoaetus melanoleucus) has relatively lower values of Vr. However, most of the Buteoninae and the Accipitrinae show high values of Vr. For digit II, Geranospiza caerulecens and the Falconidae have the highest values while the Buteoninae generally show lower ratios. Digit III exhibits the lowest range of variability among all digits and only P. haliaetus and Busarellus nigricollis, two piscivorous species, have a low Vr for this digit. Finally, digit IV has the lowest ratios among all digits. Interestingly, the PCSA results show that digit I exhibits the higher strength and digit IV the lowest, digit II and III have intermediate force values, similar to each other. Therefore, there is a commitment of the raptor distal hindlimb between speed and force: whereas digits I and III act with higher speed first and with force latter to retain the prey, digit II always acts after the first digits with strength, assuring the latter retaining of the prey.