Question of the month

Nocturnal noise

I’ve recorded the noise/call of a nocturnal creature that I would be very keen to identify.

The recording was made in deep rain forest adjacent to a freshwater creek. The noise is an intermittent high-pitched squeak. It only calls during the summer months. Despite numerous occasions of trying to spot them at night with a headlamp, I have failed as their movement seems very quick and erratic. I thought it may be a bat. What is it?


A high-pitched squeak in the night. (955 KB) mp3 document icon
Audio file supplied by John Hughes

Answer

Tube-nosed Bat caught on a barbed-wire fence. Photo: Kieran Aland. Eastern Tube-nosed Bat, feeding on a fig. Photo: Conrad Hoskin.

Your suspicion that the culprit is a bat is correct. You have recorded the distinctive call of the Eastern Tube-nosed Bat (Nyctimene robinsoni). These small fruit and blossom-feeding bats are more closely related to the larger flying foxes (megabats) than the smaller predatory (mostly insectivorous) microbats.

Our understanding is that the call that you have recorded communicates territory and may be seasonal, usually heard through summer. It is not thought to be an echolocation click or chirp like that of microbats. The higher-pitched vocalisations allow microbats to “hear” fine detail in their surroundings to catch small insect prey. It is worth noting that many of the microbats also produce vocalisations for communication and some of these are within the human auditory range. 

Tube-nosed Bats (and other megabat species) navigate their surroundings with eyesight. Even though they can see in low light, they are not sensitive to fine detail. This renders them susceptible to some of the hazards we have created in our modern world, such as barbed-wire fences.

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