AAAS QLD & NT Webinar Series: October 2020
Want to revisit a top koala-ty webinar?
Check out “A koala-ty webinar with wombats: climate change and disease in wildlife” here.
Hello Fellow Animal Enthusiasts!
Koala’s, wombats and mange Oh My! Our second last AAAS webinar for the year focused on our wild animal sector of the animal sciences. Two koala-ty Aussie scientists Dr. Scott Carver from the University of Tasmania and our own Dr. Dalene Adam from the University of Queensland enlightened us about diseases in these important Australian animals.
Dr. Scott Carver reviewed Sarcoptic mange in koalas and wombats. Mange, or scabies is a parasitic disease that can affect humans, but also koalas and wombats. Scott said Sarcoptic mange is one of the earliest known diseases in humans (1647AD!) and continues to be one of the 50 most prevalent pathogens with 100 million humans infected (Ew!) at any one time. Molecular analysis suggests that it emigrated to Australia aboard the First Fleet. Ship records indicate that some early settlers had scabies on board and these early European settlers brought with them dogs and other companion animals that helped spread it further throughout the wild animal population. A fully-fledged outbreak was observed in wombats in 1937.
Affecting 148 species of mammal, mange are not fussy about where they lay their ‘egg’ for the night! The disease presents as an epidermal infection with a 1-2 month lifecycle starting when the female mange mite digs her way into the skin of the host and lays her eggs. Symptoms due to sensitivity of the skin to the mite; include alopecia (hair loss), pruritus (desire to itch and scratch), hyperkeratosis (thickening of the skin affected skin layers), emaciation and secondary infections. The Bare Nosed wombat suffers severely from mange spread through bedding in their burrows. In koalas it is less common but they suffer similar symptoms and individuals can present severe cases. Itching and scratching can disrupt their sleep and foraging behaviour which ultimately means they can’t meet their metabolic demands, resulting in death.
Using heat maps to determine population disease fronts, it was found that as incidence of mange went up, the number of wombats went down. When compared to population transects collected by the Tasmanian government from 1985, it was found that overall, the number of wombat populations increased but key areas were declining, particularly in areas near National Parks where mange was an issue. Scott’s team trialled some treatment options using ‘burrow flaps’ coated in mange treatment for 12 weeks. However, some animals rejected the flaps and those that passed through them were not having the treatment applied in the target areas with only 33% success rate. Further, mange infected animals did recover despite the overall continued local declines in populations. Scott’s team found that if treatment could have a longer lasting effect then it would be much more successful. The team have recently received an ARC Linkage grant to try and adapt novel treatments in dogs to wombats. If this is successful, then many other animal species may also benefit from relief from mange. Good luck Scott and team!
UQ’s Dr. Dalene Adam spoke about behavioural and physiological adaptations of koalas to climate change. Considering their status as an Australian icon, surprisingly there is not much information out there about physiological capabilities and limitations. Despite having a large spread of habitable area, their current population distribution is to eastern Australia, which means that climate plays a large role in curbing populations. Koalas, use evaporative cooling by panting to dissipate heat, they do have sweat glands on their palmer and planter surfaces but these are not used for cooling. Their water comes from leaves and so death from dehydration in dry times is a problem. Climate change predictions suggest that Koala populations are likely to shrink significantly southward and eastward due to extreme climate events but there is still much that is unknown about this iconic animal. Dr. Adam’s PhD research set out to resolve some of these issues and investigate the physiological and behavioural adaptations of koalas in response to different environmental conditions with a focus on identifying critical temperature that might drive habitat and microclimate selection. The research provided some interesting and relevant findings. A free-floating temperature logger was confirmed to be safe and effective with an 18 month recording interval. This internal logger allowed the team to find that rectal temperature is on average 2°C cooler than body temperature (which ranged from 35.5 to 36.8°C during this experiment). A useful finding for vets and other field workers dealing with koalas.
Unfortunately, strict limitations on the research meant that the manipulated temperature allowed was a maximum of 28°C which was not hot enough to trigger behavioural or physiological adjustments in koalas and so, the critical threshold of adaptation could not be ascertained. However, turning lemons to lemonade, it was observed that koalas who fed in the morning had a higher heat load than koalas fed at night. This observation will help zoos and other koala management facilities to adapt management practise to better suit koalas.
Seventy-six temperature loggers deployed 1.5 m above the ground in habitat at St. Bees island were used in conjunction with GPS collars affixed to free ranging koalas. These tools helped to determine behaviour of koalas in response to heat load during the day and night. This experiment found that koalas do seek refugia from the heat, choosing food trees at night and shelter trees during the day, allowing them to capitalise on cooler regions within the shelter trees. Previous research on mapping prime koala habitat has focused on food trees only, so this is an important finding for future research on koala distribution. This is also important in climate change prediction scenarios where extreme heat events are more likely.
Thanks to both our speakers for telling us about your interesting wildlife research, and thanks for reading!
AAAS QLD & NT Branch Committee
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