Project Title: Determining critical reproductive parameters for a subtropical dugong population.
Chief Investigator: Dr Janet Lanyon
Dugongs are large, long-lived, marine mammals, with a wide distribution throughout the tropical and subtropical waters of the Indo-Pacific region. Dugongs have a very slow and highly variable reproductive rate. Previous studies on dugong carcasses have demonstrated that dugong reproductive parameters, such as age and size at sexual maturity, first reproduction and calving intervals, exhibit considerable variability in both space and time. To date, there has been no research into the reproductive parameters of free-ranging, subtropical dugongs, suggesting that the life history parameters routinely applied to some dugong populations may not be appropriate. Recent apparent declines in dugongs along the urban Queensland coast have highlighted the need for more reliable regional information on their reproductive parameters.
This project used physiological techniques to develop non-invasive methods to rapidly assess and monitor reproductive hormone levels in wild dugong populations. These techniques have been successful in achieving baseline data on the levels of male hormone (testosterone), female hormone (oestrogen) and gestation hormone (progesterone) in dugong faecal and blood samples. Significantly, amongst our sampling efforts, we have determined the reproductive hormone levels of a few pregnant females. Such information has allowed us to characterise pregnancy in individual dugongs and will contribute towards quantifying pregnancy rates in wild populations.
We collected all dugong samples from the population in Moreton Bay, which is the largest dugong population in close proximity to a major and rapidly expanding city, Brisbane. Our study has gathered baseline data on the levels of stress hormone (corticosterone) in faecal samples from wild dugongs. This will enable the assessment and quantification of chronic or acute stressors. With the rapid expansion of Brisbane city, such data will be an important tool in assessing and monitoring anthropogenic impacts that may affect the fitness or survival of the Moreton Bay dugong population.
We are still working to develop an innovative, remote sampling technique to determine hormonal profiles detected in dugong exhaled air. This part of the project will provide another potential technique for assessing reproductive status in wild dugongs.
Conservation biologists increasingly face the need to provide managers with data on causal mechanisms to better assist population management and protection. This study has established a database that will enable an assessment of reproductive status of dugongs, and will be used to predict the most effective management options for the wild dugong population in Moreton Bay.
