By Agence France-Presse
The tiny black-tailed dusky antechinus and silver-headed antechinus -- discovered in 2013 and found in wetter, higher-altitude regions of Queensland state -- are known for suicidal mating habits that include up to 14-hour sex sessions.
Climate change, habitat loss and feral pests are also threatening the mouse-like species, with scientists fearful they could soon die off in a country notorious for having the world's highest mammal extinction rate.
"They are very frantic and try and get from one mate to another and the mating itself can last hours, so it's very tiring," Queensland University of Technology mammalogist Andrew Baker said of the frenzied copulation.
Males go from "absolutely prime health... to falling to pieces before your very eyes" within the annual two-week mating period at the end of the Southern Hemisphere winter, Baker told AFP.
They have so much sex while also trying to hang on to female mates and fighting off rivals that they produce excessive levels of testosterone.
This stops a stress hormone from switching off, which then destroys their organs and kills them off.
"They're honestly like the walking dead towards the end," Baker said.
"I've seen them stumbling around during the day -- they are nocturnal mostly -- still looking for mates, bleeding from various parts of their body and their hair has fallen out."
Females have a lifespan of about two years, with more than half only breeding once and giving birth to between six to 14 babies. The males die before their first birthday.
Only three areas -- two for the silver-headed and one for the black-tailed -- in Queensland have so far been identified as home to the species, with population sizes estimated to be fewer than 250 for males and females.
Baker, who discovered both species, believes that just a few decades ago, the population was 10 times bigger.
With external pressures such as climate change reducing food sources, Baker said his team was rushing to find other populations in Australia to study how they can better protect the antechinus' habitats and save the species.
"It's a double tragedy to only just recently discover them -- and we were so excited about that, especially in a country like Australia where we have lost so many mammals -- and then now the very ones we've discovered might be lost," he added.