A new study by researchers in Australia has found that koalas have the ability to regulate their body temperatures more than previously thought.
For the first time, scientists have observed free-ranging, wild koalas drastically lowering their core body temperatures during cool mornings in preparation for the most sweltering summer days. "We have never seen this type of behaviour before in koalas,” said Dr. Valentina Mella, a zoologist with The University of Sydney’s Sydney School of Veterinary Science.
The hottest day during the study was 105.4 degrees Fahrenheit (40.8C). On that day, the research team recorded the highest ever body temperature in koalas, which was the same temperature. That morning, the team had recorded the lowest ever body temperature for a koala, which was 90.3 degrees Fahrenheit (32.3C), suggesting the marsupial regulates body temperature more than previously believed.
“This self-regulation requires individual koalas to predict days of extreme temperature from overnight and early morning conditions, adjusting their body heat regulation accordingly,” says Mella. “Our results indicate that air temperature and koala body temperature are closely aligned. What surprised us was the self-regulating animals ‘allowed’ their core temperatures to fluctuate with environmental conditions, a possible adaptive tactic to reduce evaporative cooling, saving an estimated 18 percent of water. It seems that this self-regulation of body temperature might play a more important role in surviving hotter days than known behavioural tactics, such as tree-hugging.”
So how do koalas lower their core body temperatures on cooler mornings?
“The specific mechanism is not known but it is hypothesised to have something to do with solar radiation and the redistribution of warm core blood to the cool body periphery,” Mella told EcoWatch. “The greater the solar radiation intensity in the morning, the lower the minimum core temperature would be.”
Koalas also have other ways to help them stay cool on Australia’s stifling summer days.
“Koalas have evolved specific physiological and behavioural strategies to keep cool in hot weather. They have highly insulative fur, produce concentrated urine to preserve body water, they have low metabolic rates to minimise heat production, and they pant and lick their fur to facilitate evaporative cooling. They also seek shade and adopt tree-hugging postures that promote heat exchange and they drink free water,” says Mella.
Koalas are endemic to Australia, where they can only be found in the southeast and eastern parts of the country, along the coastlines of Queensland, New South Wales, South Australia, and Victoria. They live in forests and open woodlands, typically dominated by eucalyptus tree species.