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Document Type

Open Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Degree Program

Organismic and Evolutionary Biology

Year Degree Awarded

2017

Month Degree Awarded

May

First Advisor

Elizabeth R. Dumont

Subject Categories

Biomechanics | Evolution | Integrative Biology | Other Ecology and Evolutionary Biology | Zoology

Abstract

Moles (Family Talpidae) are a classic example of extreme specialization, in their case highly derived forelimb morphologies associated with burrowing. Despite many observations of mole burrows and behaviors gathered in the field, we know very little about how and how well moles use their forelimbs to dig tunnels and to walk within the built tunnels to collect and transport food. The first chapter investigates the effect of soil compactness on two sympatric mole species under controlled laboratory conditions. My results demonstrate that increasing soil compactness impedes tunneling performance as evidenced by reduced burrowing speed, increased soil transport, shorter tunnels, shorter activity time, and less time spent burrowing continuously. Furthermore, differences in performance between the two mole species may be associated with differences in the structure and extent of their burrow systems or the morphology of their forelimbs. The second chapter investigates the kinematics of Eastern moles burrowing in loose and compact substrates. Using XROMM (X-ray Reconstruction of Moving Morphology), I found that moles move substrate dorsally using elevating strokes in loose substrates and laterally using scratching strokes in compact substrates. They do not move the substrate caudally like most mammalian forelimb diggers. Furthermore, my results demonstrate that the combination of stereotypic movements of the shoulder joint, where the largest digging muscles are located, and flexibility in elbow and wrist joints makes moles extremely effective diggers in both loose and compact substrates. In the third chapter I test two hypotheses about forelimb movements during walking. The first is that moles move their shoulders by humeral long-axis rotation, as they do during burrowing and in walking echidnas. The second is that moles move their shoulders by flexion and extension in the horizontal plane, similar to sprawling reptiles. Surprisingly, my results reject both hypotheses and indicate that the way moles walk is different from that of all tetrapods that have been studied. The results of my dissertation open new horizons in the study of morphological, physiological, behavioral and ecological evolution of fossoriality, and may provide new ideas for the design of bio-inspired robots used for urban search and rescue.

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