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Size relationship of the tympanic bullae and pinnae in bandicoots and bilbies (Marsupialia: Peramelemorphia)

Taylor, Melissa (2019) Size relationship of the tympanic bullae and pinnae in bandicoots and bilbies (Marsupialia: Peramelemorphia). Honours thesis, Murdoch University.

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Hearing is an important factor allowing species to obtain information about their environment. Variation in tympanic bullae and external pinnae morphology has been linked with hearing sensitivity and sound localisation in different mammals. Bandicoots and bilbies (Order Peramelemorphia) typically occupy omnivorous niches across a range of habitats from open, arid deserts to dense, tropical forests in Australia and New Guinea. The morphology of tympanic bullae and pinnae varies between peramelemorphian taxa. Little is known about the relationship between these structures, or the extent to which they vary with respect to aspects of ecology, environment or behaviour.

This thesis investigated the relationship between tympanic bulla and pinna size in 29 species of bandicoot and bilby. Measurements were taken from museum specimens to investigate this relationship using direct measuring methods and linear dimensions. It was hypothesised that an inverse relationship between bullae and pinnae may exist and that species residing in arid regions would have more extreme differences. Environmental variables were examined to determine the level of influence they had on bullae and pinnae.

This study found that there was a phylogenetic correlation between the structures and that they were significantly influenced by temperature (max/average) and precipitation
(average). Species which inhabited more complex, temperate habitats had relatively smaller bullae and pinnae than those in less complex, more arid habitats. Species tended to have either a relatively larger bulla or pinna, with the relationship being more pronounced in species in more arid habitats. No inverse relationship was found between relative bulla and pinna size. Previous studies have found a relationship between relative bulla and pinna and predator evasion tactics; the findings of this study appeared to support this.

These findings suggest that ecological traits and habitat types may be linked with relative bullae and pinnae sizes.

Item Type: Thesis (Honours)
Murdoch Affiliation(s): School of Veterinary and Life Sciences
Supervisor(s): Warburton, Natalie, Fleming, Trish and Travouillon, Kenny
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