We performed comparative analyses of four cross-sections of the distal radius and tibia in two species of macaque to clarify
the relationships between bone morphology and locomotor type. The lengths of bones and five bone geometric properties in each
section were examined and compared separately in both female and male
Macaca mulatta and
Macaca fascicularis. In
M. mulatta, there were no significant gender-specific differences in either the radius or the tibia. In contrast, the radius and tibia
of male
M. fascicularis had greater geometric parameters in the 20% and 40% positions relative to the 5% and 10% positions from the distal end than
those of their female counterparts. The radius and tibia of
M. mulatta were relatively longer than those of
M. fascicularis, and the sectional parameters of the tibia of
M. mulatta were relatively larger than those of
M. fascicularis. Standardization of the log-transformed bone length between the species revealed larger radial cortical bone areas in
M. fascicularis. In contrast, there were minimal differences in the tibial cortical bone areas between the two species. This study suggests
that the observed distinctions in bone geometry in female and male
M. fascicularis may be due to gender-specific differences in the muscle weights of the forearm and calf, which may underlie the divergence
in the leaping abilities of females and males of this species. Taken together, these results of interspecies comparisons may
be related to the fact that arboreal primates such as
M. fascicularis undergo compressive mechanical stress due to the forelimb lead that occurs as the animal descends a sloping trunk or bridges
a tree gap downward, while terrestrial primates such as
M. mulatta move on nearly flat substrates. Differences in fore- and hind-limb bone properties between the two species are discussed
with regard to functional morphology and locomotor type.
Keywords Locomotion -
Macaca
- Cortical bone - Terrestrial - Arboreal