Title

Auditory characteristics of the dugong ear

Objective

To determine the auditory characteristics of the dugong ear with respect to its acoustic capabilities and sensitivity to pressure wave injury.

Relevance

This project forms part of the dugong research program being funded by Defence to assess the effects of underwater explosions which are conducted at two intertidal sites at Triangular Island during occasional Clearance Diver training courses. The underwater hearing abilities of marine mammals remain relatively poorly understood due to their size and difficulty of conducting research in open water environments. This is particularly the case for shy sirenian mammals such as the dugong. The results will therefore be valuable for auditory zoologists in general, as well as for environmental appraisals of other noise-generating activities such as boating and underwater seismic exploration by the petroleum industry.

Feasibility

Based on work already undertaken elsewhere, particularly that on the Florida manatee at the Woods Hole Oceanographic Institute, a comparative morphological and histological investigation of preserved dugong skulls and ear structures will enable the auditory characteristics to be determined. It is hoped that this project can include a manipulative study using 1–2 dugong heads taken from fresh carcasses. This will allow the project to provide a reliable estimate of both auditory capabilities and pressure thresholds that could injure the middle ear (a sensitive structure present in all mammals and considered the most susceptible to pressure wave damage).

Methodology

Defence plans to contract Dr Darlene Kettern (Woods Hole) to undertake the various morphological, histological and manipulative studies using the same techniques she pioneered for her studies of the Florida manatee. Because the project relies heavily on obtaining suitably preserved dugong material from fresh carcasses, the first stage will involve Dr Kettern’s training of selected staff from James Cook University and rangers from Queensland Parks and Wildlife Service on some basic field triage and preservation techniques.

Approximate Cost

Likely to be ~$150 000 (based on initial data from Dr Kettern, including travel costs from the United States).

Time Required

Approximately 18–20 months from August 1999