Sex-mad males attract University research
Some Australian males are obsessed by sex and a University of Queensland researcher has spent a couple of years trying to find out why.
For her PhD, Charlotte Toftegaard is studying hormonal control of chemical communication and behaviour in the brown antechinus, a small, mouse-like marsupial commonly found in Queensland rain forests.
The male antechinus never survives longer than 12 months and in that year of living dangerously most of its energy is channelled into a frantic and frenzied urge to mate.
Previous research has shown that around May of each year the hitherto solitary males suddenly become gregarious, form nesting groups and begin "lekking", a ritual display to attract females.
The mating season lasts for the next two or three months and such is the dedication of the males to the task at hand that they neglect to eat and basically wear themselves out.
Ms Toftegaard said that by September the males were looking haggard and drawn, were riddled with parasites, developed ulcers and finally the stress of it all caused fatal haemorrhaging from gastric ulceration.
"You won't find any adult males in the forest past October. They are all dead," said Ms Toftegaard, who has set out to discover just what triggers this extraordinary behaviour and life cycle.
Ms Toftegaard, who has a bachelor of science degree from the University of Copenhagen in her native Denmark and gained honours for a study in bird ecology at St Andrews University, in Scotland, began studying marsupial biology at UQ in 1996.
She said there were nine species of antechinus on mainland Australia and the prospects for female browns were less gloomy. Though they bred only once a year they could have as many as 10 young and by the time they were all weaned, up to half the mothers died of exhaustion.
The young are born around October or November and attach themselves like little kidney beans to the mother's teats. However, by February or March, when they are weaned, the mother is dragging them around on the ground.
"Interestingly, this whole stress thing and premature death doesn't affect the brown antechinus we have in the laboratory because they have no social contact. Some of these have lived quite happily up to five years," Ms Toftegaard said.
Findings from her research may play a part in promoting breeding among rare species or inhibiting reproduction in cases where over-population is becoming a problem.
Using a range of University facilities - from magnetic resonance imaging to microscopy and microanalysis - Ms Toftegaard has been studying hormonal and chemical changes in these tiny marsupials.
She has found that during the breeding season, male brown antechinus are awash with testosterone, the principal male sex hormone. At the same time she found continuous high levels of the steroid hormone cortisol.
Otherwise known as hydrocortisone, this compound is important in the normal response to stress but in the excessive quantities present in the antechinus, it has the opposite effect and causes gastric ulcers.
Ms Toftegaard is also trying to discover what triggers the sudden "lekking" and is concentrating on the role played by odours found in the marsupials' urine and in secretions given off from chest glands.
"I have been analysing the urine and found some very interesting compounds. I have also been looking at how these influence stress levels and reproductive profiles," she said.
"It appears the animals are drawn together for ?lekking' by scent and the scent glands may also be the key to individual recognition."
In support of this theory, Ms Toftegaard has discovered the antechinus have a very large and active vomeronasal organ in their noses specifically for perceiving pheromones, chemical substances given off as signals between animals.
Pheromones, which can be used to attract mates and promote social cohesion in colonies of animals, are so powerful they can be effective in the most minute concentrations.
Ms Toftegaard said one practical application of her research might be in the area of conservation of endangered species which could be encouraged to mate and reproduce by subjecting them to the right chemical smells.
Conversely, animals which were becoming a pest through over-population, such as possums in New Zealand, could be discouraged from breeding by neutralising certain scents and associated chemical and hormonal impulses.
For further information, contact Ms Charlotte Toftegaard (telephone 3365 2720).
