Explore our Indian flying foxes (Pteropus medius) thermoregulatory behavior guide.

Pteropus medius are often vulnerable to high temperatures as they have exposed open roosting structures and are devoid of sweat glands, contributing toward their lower thermal tolerance than similar size mammals. Thermal or thermodynamic tolerance is an animal’s ability to balance thermogenesis and heat dissipation under ambient temperatures that exceed the thermoneutral zone. As a result, Pteropus have adopted various thermoregulatory behaviors and strategies, such as increasing the exposed surface area of their wings or enhancing evaporative cooling by salivation. The intensity, frequency and duration of the thermoregulatory behaviors increases in a sequential manner, starting with wing fanning to induce forced convection, followed by clumping and clustering to reduce exposure to solar radiation exposure, lastly, salivation (wrist licking), belly soaking and panting to induce evaporative cooling.

These flying foxes eventually collapse due to hyperthermia when ambient temperatures exceed 43°C. In hotter season, Indian flying foxes spend less time sleeping and resting because they engage in more thermoregulation. This sleep deprivation is known to negatively affect cognitive responses, physiological traits, and overall alertness. Ultimately, continued exposure to extreme heat results in early deaths.