Measuring physiological stress in Australian flying-fox populations

Area of Science:

• Veterinary Medicine
• Wildlife Ecology
• Zoonotic Disease Research

Background:

• Flying-foxes (pteropid bats) are natural reservoirs for the Hendra virus, a zoonotic pathogen impacting horses and humans in Australia.
• Physiological stress has been implicated as a risk factor for Hendra virus infection in flying-foxes, yet stress hormone levels remain understudied.
• Understanding stress physiology in flying-foxes is crucial for managing Hendra virus transmission dynamics.

Purpose of the Study:

• To establish a method for measuring stress hormones in flying-foxes.
• To determine population-level urinary cortisol ranges for four Australian flying-fox species.
• To assess the utility of urine specific gravity as a correction factor for urine concentration.

Main Methods:

• Collected pooled urine samples from roosting flying-foxes and individual urine/blood samples from captured bats over 12 months.
• Assayed urine and plasma samples for cortisol using a commercial enzyme immunoassay.
• Validated urine specific gravity as an alternative to creatinine for correcting urine concentration.

Main Results:

• Demonstrated a typical stress response in flying-foxes following capture.
• Established population-level urinary cortisol ranges and geometric means for Pteropus alecto, P. conspicillatus, P. poliocephalus, and P. scapulatus.
• Found significant differences in geometric means among species, except between P. alecto and P. conspicillatus.

Conclusions:

• Developed a robust methodological approach for assessing stress in flying-foxes.
• The established urinary cortisol ranges provide a valuable baseline for wildlife health monitoring and research.
• This approach can be applied to other free-living, colonial wildlife species for stress assessment and disease management.