Numbats are one of Australia’s most distinctive and endangered marsupials. They are the only marsupials that feed exclusively on termites, which they dig out from the ground with their long tongues. They are also active during the day, unlike most other marsupials that are nocturnal. However, these traits may also make them vulnerable to the effects of climate change, which is expected to increase the temperature and aridity of their habitat.
Numbats live in the dry woodlands and forests of Western Australia, where they face high levels of solar radiation, air temperature, ground temperature, and humidity. These factors affect their body temperature, which they need to keep within a safe range of 32°C to 40°C. If their body temperature gets too high, they can suffer from heat stress, dehydration, and organ damage. If their body temperature gets too low, they can lose energy and become more susceptible to predators.
To regulate their body temperature, numbats use various strategies, such as seeking shade, resting in hollow logs, grooming their fur, and panting. However, these strategies also have costs, such as reducing the time and energy available for foraging, increasing the risk of predation, and losing water through evaporation. Therefore, numbats need to balance their heat and food requirements, which can be challenging in a changing climate.
Infrared cameras reveal numbat thermal ecology
To understand how climate change affects numbats, researchers from Curtin University and the University of Western Australia used infrared cameras and computer models to measure the surface temperature and heat exchange of numbats in two reserves in Western Australia. They filmed about 50 numbats during 2020 and 2021, and also recorded the environmental conditions, such as air temperature, relative humidity, solar radiation, and wind speed.
The researchers found that numbats gained heat quickly when they were exposed to direct sunlight, which accounted for 18% of their heat gain. However, they also gained heat from the air and ground, which accounted for 82% of their heat gain. Even when they retreated to the shade, they still gained heat from their surroundings, especially from the heat radiating from objects in the environment. The researchers also found that humidity reduced the effectiveness of panting as a cooling mechanism.
Using computer models, the researchers calculated how long numbats could forage in the sun before their body temperature reached 40°C, which is the upper limit of their thermal tolerance. They found that if the air and ground temperatures (not the temperature in direct sunlight) increased to 23°C, the numbats were only able to remain in the sun for 10 minutes before they had to seek shade. This poses a huge problem for the numbats, as their only food source is termites, which are most abundant and accessible during the day.
Climate change threatens numbat survival
The researchers concluded that climate change poses a serious threat to the survival of numbats, as it will increase the frequency and intensity of heat waves and droughts in their habitat. This will reduce the availability and quality of their food, as well as their ability to cope with heat stress. The researchers estimated that by 2070, the numbats will experience lethal body temperatures for more than half of the year, even in the shade.
The researchers suggested that conservation efforts for numbats should focus on protecting and restoring their habitat, especially the areas with dense vegetation cover, which can provide shade and reduce heat radiation. They also recommended that more research should be done on the effects of climate change on other aspects of numbat ecology, such as reproduction, behavior, and physiology.
The researchers hope that their study will raise awareness and inspire action to save the numbats from extinction. They said that numbats are not only important for the biodiversity and cultural heritage of Australia, but also for the ecosystem services they provide, such as controlling termite populations and enhancing soil fertility.