Mass dying events and heat stress events

Mass dying events are commonly caused by heat stress, but can also occur from natural disasters such as fire, cyclone and trees falling over, as well as food shortages. Heat stress events are generally days where the temperature exceeds and stays above 38°C, which is more likely to occur in the warmer months of November to February.

Heat stress occurs when flying-foxes can no longer regulate their body temperature, often collapsing out of trees from hyperthermia (Welbergen et. al., 2008). Watch out for the signs of distress in the figure below.

Heat stress, and responding to heat stress events, is discussed further in the Roost Management Guideline (PDF, 3.3MB)

Stages of heat stress in flying-foxes

  • Category 1—Normal
  • Category 2—Minor stress - wing fanning
  • Category 3—Moderate stress - seeking shade and clustering
  • Category 4—Major stress - clumping, salivating, licking wrists and panting
  • Category 5—Critical stress - collapsing and falling from trees
  • Deceased