How the snipe makes its drumming sound

Comparative Biochemistry and Physiology, Part A 153 (2009) S114–S133 Contents lists available at ScienceDirect Comparative Biochemistry and Physiology, Part A j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / c b p a Society for Experimental Biology Annual Main Meeting 28th June — 1st July 2009, Glasgow, UK A6 — GENERAL BIOMECHANICS A6.1 A6.2 09:00 Sunday 28th June 2009 What makes a great footballer? Trade-offs between athleticism and skill in human performance 09:20 Sunday 28th June 2009 Functional and behavioral limits on human hammering performance Robbie S. Wilson (The University of Queensland) Duncan J. Irschick (University of Massachusetts at Amherst), Suellen Almeidac (University of Massachusetts at Amherst) Animal performance during critical behaviours such as predatorescape, prey-capture and fighting ability is determined by a complex assortment of underlying traits. Maximal physical capacity is widely appreciated to be an important determinant of performance during these complex behaviours. However, the role of individual skill in determining performance is virtually unknown and its role in the evolution of physical function has been surprisingly dismissed. Skill is likely to be a key determinant of performance for many complex behavioural traits. For example, male fighting capacity is likely to be determined by more than just strength alone, but also fighting technique, coordination, and decision-making. Given the difficulties associated with assessing skill in non-human organisms, we used analyses of human performance to investigate the possible interactions and trade-offs between skill and athletic ability. Performance of individuals during staged one-on-one football games was used as our model complex performance trait. Footballing ability was assessed for 30 subjects (aged 17–31 years) and their performance in 16 different athletic and skills tasks was also quantified. We competed ten different models that evaluated the relationships between individual morphology, athleticism and skill to overall footballing performance. We found that most maximal athletic tasks were positively correlated, as were many skill component tasks. However, there was no evidence of any positive or negative correlations between maximal athletic performance and skill, suggesting that these traits may be completely independent and under different selective pressures or even under separate genetic control. Implications of this work for the evolution of vertebrate physical performance will be discussed. Email Address for correspondence: [email protected] doi:10.1016/j.cbpa.2009.04.170 One of the most fundamental trade-offs in any biomechanical system concerns that between force and velocity during a challenging motor task. How organisms cope with these seemingly conflicting functional demands is poorly understood. We study human hammering as a simple yet challenging motor skill that requires both high force and high accuracy. In particular, we have been studying which factors influence force–velocity relationships during hammering, including the degree of light (light versus dark), gender (male versus female), target size, and degree of learning. Our results indicate that all of these factors affect force–velocity relationships but in a complex manner, with significant individual variability that may be a signature of human performance. Email Address for correspondence: [email protected] doi:10.1016/j.cbpa.2009.04.171 A6.3 09:40 Sunday 28th June 2009 How the snipe makes its drumming sound Roland Ennos (University of Manchester), Adam Van Casteren (University of Manchester), Jonathan Codd (University of Manchester), James Gardiner (University of Manchester), Henry McGhie (Manchester Museum) Male common snipe (Capella gallinago gallinago) produce a “drumming” sound with their outer tail feathers during their mating dives, but little is known about how this is achieved. We investigated the movements and sound producing capabilities of the outer tail feathers. Using a wind tunnel, we compared observations of the frequencies of sound produced with the predictions from aerodynamic theory. The Abstracts / Comparative Biochemistry and Physiology, Part A 153 (2009) S114–S133 feathers were also filmed in an air-flow with a high speed video camera, and subjected to morphological examination and biomechanical testing. Video and audio analysis of the feather demonstrated that a fluttering of the trailing vane generated the sound. The flutter of the vane is facilitated by the rearward curvature of the feather shaft, reduced branching angles of the barbs in the trailing vane and the lack of hooks on the barbs, all of which increase the flexural compliance of the trailing vane, especially in a hinge region. Sound production occurred at the same frequency as the vane movements, at frequencies consistent with it being produced by a fluttering flag mechanism but too high to be caused by an Aeolian whistle mechanism. Email Address for correspondence: [email protected] doi:10.1016/j.cbpa.2009.04.172 A6.4 10:00 Sunday 28th June 2009 Spring or strut? Biomechanical specialisations in elephant limbs Charlotte E. Miller (Royal Veterinary College), Dimitrios Tsaopoulos (Royal Veterinary College), John R. Hutchinson (Royal Veterinary College) S115 Morphological parallelism between South American hystricomorph rodents and small ungulates from the Old World has been postulated for a long time. This research deals with this question from the point of view of biomechanical characteristics of the long bones. For that, cross-sectional area, second moment of area, polar moment, athletic ability indicators and strength were calculated for the long bones (humerus, radius, femur and tibia) of 5 species of Cavioidea and 2 species of Artiodactyla. Regressions of each of these variables to body mass were carried out. Regarding the cross-sectional area, the confidence intervals show that the exponents calculated are always higher than the value predicted by geometrical similarity, except in the case of the femur, while exponents obtained for the second moment of area or the polar moment are not significantly different from the predicted values, except for humerus and tibia. The two indicators of athletic ability scaled as expected, except the humerus and tibia axial indicators. The exponent calculated for femur strength is not different from 0, while in the case of the humerus, strength decreases slightly with body mass. Additional statistical tests show no difference between the values of these parameters calculated for the studied samples of artiodactyls and rodents. The present results are consistent with the hypothesis that the parallelism between hystricomorph rodents and small ungulates is very important. Email Address for correspondence: [email protected] doi:10.1016/j.cbpa.2009.04.174 The fore- and hindlimbs of elephants contain several specialised muscle–tendon units and fasciae. Differences in fore- and hindfoot form and function, with a spring-like ankle and strut-like wrist, appear to be balanced by differences in more proximal limb anatomy, consistent with measurements of similar overall mechanical functions in both limbs. Here we present qualitative and quantitative anatomical data on the limb specialisations of elephants, with particular reference to the changes in morphology seen across a wide ontogenetic size range (~ 100–4000 kg). These are then integrated with available biomechanical data to infer possible locomotor function. Elastic structures are more developed in the proximal fore- than hindlimb and become more extreme during growth. Pronounced flexion of the forelimb appears to be the default position when the muscles are inactive, as indicated by the normal orientation observed post-mortem. This flexed limb configuration is maintained, at least in part, by tension in the thick fascial layers covering the muscles, and is much more pronounced than in the hindlimb. The elephant forelimb also contains two muscles which have become remarkably specialised when compared with the ancestral mammalian condition. The pronator teres forms a thick, fibrous band in larger elephants, fixing and stabilising the wrist joint in pronation. The flexor carpi radialis muscle is strongly compartmentalised by yellow elastic tissue, creating a long, springy connection between the radius and the carpus. This unusual structure may aid in damping the “heelstrike” impulse at the carpus, making wrist and ankle function more similar in the living elephant than seen in in vitro experiments. Email Address for correspondence: [email protected] doi:10.1016/j.cbpa.2009.04.173 A6.5 10:40 Sunday 28th June 2009 Geometry and parallelism in the long bones of rodents and ungulates Adrià Casinos (University of Barcelona), Oscar Rocha-Barbosa (Universidade do Estado do Rio de Janeiro), Eloy Gálvez-López (University of Barcelona) A6.6 11:00 Sunday 28th June 2009 Allometric scaling of trabecular bone Michael Doube (Imperial College London), Sandra J. Shefelbine (Imperial College London), John R. Hutchinson (The Royal Veterinary College), Alexis M. Wiktorowicz Conroy (Imperial College London), Michal M. Kłosowski (Imperial College London) The scaling of gross bone shape with size is well-studied. However, the mechanically important interior micro-architecture of bones has been more neglected. We measured trabecular scaling in a broad range of taxa, spanning the 6 orders of magnitude size range from Etruscan shrews (Suncus etruscus) to Asian elephants (Elephas maximus). We acquired 3D microtomographic scans (Metris X-Tek) of entire femoral heads (femoral head radius, R < 7.5 mm) or of 10 mm cubes cut from the centre of the femoral head (R > 7.5 mm). We cropped images to contain only trabecular bone and then binarised them. Trabeculae tend to increase in thickness as R increases, with greatest maximum thickness (Tmax) attained in elephant trabeculae (Tmax ∝ R2.6). For perspective, the radius of a mouse's (Mus musculus) femoral head is similar to the thickest elephant trabecula (both 0.77 mm). For small animals with R < 10 mm, mean trabecular thickness (Tav) scales strongly with R (Tav ∝ R2.4). Greatest mean trabecular thickness (0.197 mm) was found in relatively small animals – the mountain hare (Lepus timidus) and greater mouse deer (Tragulus napu) – possibly related to high acceleration propulsion by the hindlimbs. Trabecular thickness is not associated with volume fraction. Bone volume fraction and anisotropy did not scale with animal size, remaining within a similar range independent of animal size. Measurement of trabecular network parameters such as branch length, connectivity and rod/plate distribution may explain why the largest animals do not have relatively the most trabecular bone. Email Address for correspondence: [email protected] doi:10.1016/j.cbpa.2009.04.175