Determining the age of the Eastern Grey Kangaroo based on their mandibular features and measurements

Dougheney-Earle, Riley 2021, Determining the age of the Eastern Grey Kangaroo based on their mandibular features and measurements, B. Science (Hons) thesis, School of Life and Environmental Sciences, Deakin University.

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Title Determining the age of the Eastern Grey Kangaroo based on their mandibular features and measurements
Author Dougheney-Earle, Riley
Institution Deakin University
School School of Life and Environmental Sciences
Faculty Faculty of Science, Engineering and Built Environment
Degree type Honours
Degree name B. Science (Hons)
Thesis advisor Weldon Elizabeth A.ORCID iD for Weldon Elizabeth A. orcid.org/0000-0002-1147-8785
Date submitted 2021
Summary The Lancefield megafaunal site is a swamp deposit comprised of over 10,000 fossilised bones, about 90% of which are from an extinct sub-species of kangaroo (Macropus giganteus titan). These bones have been estimated to be between 40,000 and 60,000 years of age. If the age in years of these kangaroos at death can be determined, this information may be able to help ascertain if the death assemblage is the result of natural attrition or a catastrophic event.

This study aims to develop a new method for assessing the age of eastern grey kangaroos (Macropus giganteus) based on their mandibles, which can later be applied to the Lancefield megafaunal site.

Three methodologies were followed to determine if an estimation of the eastern grey kangaroo’s age could be established. Kirkpatrick’s method of molar indexing was modified and applied on the mandible, and follow-up measurements were taken measuring the distance of the final molar past the established reference point. A logarithmic regression analysis determined that mandibular molar indexing could determine the age of the eastern grey kangaroo until age 5.5 years. For every subsequent year, the linear regression analysis revealed that the posterior molar will move a further 1.61 mm past the reference point.

The diastema length was measured on all mandibles. The linear regression showed no significant relationship with age, and thus this was not an appropriate method of determining the age of the eastern grey kangaroo.

Measurements for mandibular body height, body length, body robustness (length x height), ramus breadth, ramus height, ramus robustness (height x breadth) and angle were measured with digital callipers. 2D robustness measurements were also taken as height x width at the apex of the mandibular arch and the posterior of the mental foramen. The Welsh’s t-test found that the body robustness and mandibular arch robustness increased with age, but only in the male populations. As there is no established method of determining gender based on the mandible, this will not be an appropriate method of determining the age of the eastern grey kangaroo.

Language eng
Indigenous content off
Description of original 57 p.
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Persistent URL http://hdl.handle.net/10536/DRO/DU:30154678

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