Meeting Abstract
Forelimb strokes are used to propel animals through substrates in many forms of locomotion, including flying, swimming, sculling and burrowing. Moles, one of the most specialized mammalian diggers, are thought to burrow through the earth with swimming-like lateral strokes, but the kinematic details of the mole’s lateral stroke remains unclear. In this study, we analyzed the 3D pattern of 83 lateral strokes from 3 Eastern moles using biplanar video radiography combined with model-based motion analysis (XROMM). We allowed the animals to burrow in couscous and traced the movement of the tips of the third digits. We found that the path of the lateral stroke has much more of a lateral component than a posterior component. The stroke ends with the two hands parallel to the body axis with palmar surface facing outward. This contradicts the previous view that lateral strokes end with the hands facing posteriorly as in swimming. We also found that the stroke span, the maximum distance between claw tips, is somewhat wider than body width. 77% of the strokes have a span that is 90-140% of body width, but only 2% of the strokes are over 160% of body width. Finally, we found that moles alternate their right and left hands during burrowing. 65% of the strokes we surveyed were asymmetric: one hand moved the substrate laterally while the other hand braced against the substrates. Our findings suggest that the lateral stroke of Eastern moles is unlike any type of swimming stroke and is also distinct from the stroke used by scratch diggers.
