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A race against heat: The numbat's fight for survival

Australia, a land known for its unique and captivating wildlife, faces a grim reality with the increasing threat of climate change. 

Marsupials in arid regions are particularly at risk, as rising temperatures may exceed their survival thresholds. Among these is the numbat, a termite-loving marsupial that is already struggling with escalating heat.

The heat limits of numbats 

Researchers Christine Cooper from Curtin University and Philip Withers of the University of Western Australia have conducted on an innovative study to understand the impact of rising temperatures on the numbat. 

Utilizing infrared cameras and advanced computer models, the researchers sought to determine the heat limits that numbats can withstand before succumbing to the harsh environment.

Alarming findings 

The team discovered that numbats can only forage under the sun for approximately 10 minutes in high temperatures before needing to seek refuge in the shade. 

With increasing ambient temperatures and humidity, the shade may soon be insufficient for their survival.

How the research was conducted

In an unprecedented field study during 2020 and 2021, Cooper and Withers traversed the forest paths of Western Australia’s Dryandra Woodland and Boyagin Nature Reserve. 

The researchers filmed around 50 numbats using infrared technology, simultaneously measuring environmental factors like air temperature, humidity, solar radiation, and wind speed. This comprehensive approach provided a holistic view of the numbat’s struggle against the elements.

Numbats, uniquely diurnal among marsupials, spend 62% of their time under the sun. The researchers meticulously measured the surface temperatures of different body parts of the numbat, both in sunlight and shade. 

Troubling insights

The experts determined that direct sunlight was responsible for a mere 18% of the numbat’s heat gain, indicating other significant heat sources at play. The investigation revealed that, at peak temperatures, numbats continued to absorb heat even in the shade. 

The team discovered that air and ground temperatures, along with heat radiating from surrounding objects, are the primary contributors to the risk of overheating in numbats. This means that even shaded environments may soon become too hostile for these marsupials to cool down.

Dangerous body temperature threshold 

The researchers analyzed the amount of time that numbats could hunt for food before their body temperature reached a critical 40°C. 

They discovered that at air and ground temperatures of 23°C, numbats could only sustain 10 minutes of sun exposure before reaching this dangerous body temperature threshold. This presents a dire situation for numbats, whose sole diet consists of termites. 

Since termites are not particularly nutritious, numbats must consume them in large quantities for survival. However, termites ascend near the surface only when the ground is sufficiently warmed by the sun, limiting the numbats’ feeding to daylight hours.

An uncertain fate

The future for numbats, under the current trajectory of climate change, is increasingly precarious. Nighttime foraging is not a viable alternative due to the inaccessibility of termites and heightened predation risks. 

Furthermore, if the climate continues to warm as projected, even shaded areas will not provide the necessary relief from the accumulating heat in the air and rocks.

The study suggests that if immediate action is not taken to curb global temperature rise, the numbat could become yet another tragic casualty of climate change.

The study is published in the Journal of Experimental Biology.

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