 Because most dugongs look alike, we apply tags in order to identify them at later recaptures. We use a system of multiple tags since at this stage we are not certain how long different types of tags will remain on the animals. For each captured dugong, we apply a uniquely-numbered titanium turtle tag to the tail fluke and a microchip PIT tag to the shoulder region. We also take a small notch out of the trailing edge of the fluke (a 'cookie') using a cattle ear notcher: this gives us an additional physical marker, but also a tissue sample for stable isotope analysis. A small skin scraping from the dorsum is used for genetic analysis. We are using DNA profiles at 26 microsatellite loci to routinely identify individuals, assign paternity, construct pedigrees, detect population structuring and estimate rates of physical tag loss.
A series of photographs of each dugong allows us to record any distinguishing features (e.g. scars or old injury) which may be useful in identifying an individual.
In addition to tagging a dugong, we measure it and collect a number of samples at each capture. Body measurements include body length and a series of girth measurements to assess body condition of the animal, i.e., how fat it is. We also sex the dugong then take a small faecal sample to check levels of reproductive hormones to determine reproductive status. If a dugong has unusual pathology, appropriate samples are also taken.
View a video of the team tagging and sampling a dugong.
Please note: This video file has been compressed for download viewing, and should open automatically in Windows Media Player on a PC. It is best viewed at set (100%) resolution; viewing in larger or 'full screen' resolution will result in a poor picture. To view on a Mac computer, a suitable viewing program should be installed; Windows Media Player for Mac may be downloaded from Microsoft.
This video , "Reef Dreams" was produced by Iguana Films, and they have kindly made the segment available to the website for research and educational purposes only (not for commercial use or screening).
We now have substantial numbers of dugongs that have been caught in consecutive years. All dugongs have individual ID numbers and have been named to make it easier to keep track of individuals. At recapture, dugongs are measured so that growth rates can be determined, sex is confirmed and a small skin biopsy confirms genetic identity.
This project is a long term one which will yield data on growth and life history of wild dugongs in Moreton Bay. The mark-recapture program has expanded recently to include the dugong populations in the more northern Hervey and Shoalwater Bays. These bays hold the nearest dugong populations to Moreton Bay. At this stage animals in these areas are not captured as part of the program. Instead, a small tissue sample from the dorsum of the dugong is collected remotely from the boat using a biopsy implement attached to a long pole. Through DNA analysis and genetic mark-recapture, we are examining structure and size of these populations, and relatedness and migration between populations over regional scales.
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