Differential sex-specific walking kinematics in leghorn chickens (Gallus gallus domesticus) selectively bred for different body size

Abstract

The differing limb dynamics and postures of small and large terrestrial animals may be mechanisms for minimising metabolic costs under scale-dependent muscle force, work and power demands; however, empirical evidence for this is lacking. Leghorn chickens (Gallus gallus domesticus) are highly dimorphic: males have greater body mass and relative muscle mass than females, which are permanently gravid and have greater relative intestinal mass. Furthermore, leghorns are selected for standard (large) and bantam (small) varieties and the former are sexually dimorphic in posture, with females having a more upright limb. Here, high-speed videography and morphological measurements were used to examine the walking gaits of leghorn chickens of the two varieties and sexes. Hindlimb skeletal elements were geometrically similar among the bird groups, yet the bird groups did not move with dynamic similarity. In agreement with the interspecific scaling of relative duty factor (DF, the proportion of a stride period with ground contact for any given foot) with body mass, bantams walked with greater DF than standards, and females walked with greater DF than males. Greater DF in females than in males was achieved via varietyspecific kinematic mechanisms, associated with the presence/ absence of postural dimorphism. Females may require greater DF in order to reduce peak muscle forces and minimise power demands associated with lower muscle to reproductive tissue mass ratios and smaller body size. Furthermore, a more upright posture observed in the standard, but not bantam, females, may relate to minimising the work demands of being larger and having proportionally larger reproductive tissue volume. Lower DF in males relative to females may also be a work-minimising strategy and/or due to greater limb inertia (as a result of greater pelvic limb muscle mass) prolonging the swing phase.

Examining the accuracy of trackways for predicting gait selection and speed of locomotion

“…Many birds and other animals use transitional gaits, suggesting this issue is likely widespread in extinct forms as well. Other unknowns, not quantified in the current study, but likely to further cloud the inferences from tracks in isolation are the influence of sex differences on the kinematics of locomotion [16,[68][69][70] and ontogenetic influences [21] all of which cannot be quantified in extinct animals. Inferences into the biology of extinct forms commonly suffers from large errors [60,61,71] and rely on numerous assumptions when extrapolating from extant to extinct forms [65,72,73].…”

Body proportions for the facilitation of walking, running and flying: the case of partridges

“…Total length and trunk inclination explains this variation; consequently, total length is important to walking and flying [ 44 ]. According to their mass and related to their total length, partridge age-sex classes scale their CoM position with regards to walking and flying [ 45 ]. CoM position and body proportions affect mobility; less mass and better balance facilitates escape terrestrially and aerially [ 46 ].…”

Sex Determination in Male and Female Melopsittacus undulates using a Morphometric Method

“…This study found that the body weights of females are higher than the males. This is because the female have to incubate eggs while the male spends time looking for food and feeding until the baby birds fledge (Rose et al, 2016). Another factor that influence the weight difference is testosterone hormone.…”