Owls are a common but often overlooked predator of small mammals in Australia. Though they don't exact the same toll as feral cats, they're expert hunters using sight and sound to locate their nocturnal prey.
A quirk of owl feeding behaviour is that they need to disgorge the indigestible components of their prey. These are produced as owl pellets, or as I like to call them, owl vomit. And they're really useful to us ecologists.
Owl pellets are packed full of information about the prey, in the form of skeletal remains, fur or feathers. These are readily identifiable and provide data about what species occur in the local area, and how the species present in the landscape change over time.
For example, Barn Owl roosts with pellets dating back beyond European settlement at Camooweal Caves in north-western Queensland provided evidence of the occurrence of now-extinct species such as the Western Quoll and Brush-tailed Rabbit-rat. Barn Owls may hunt up to 10 km from their roosts, so we know that species found in pellets occur or were previously present within that distance from where pellets are found.
Last week I travelled with Dr Pippa Kern (Bush Heritage ecologist at Edgbaston Reserve) to investigate a cave known as Bat Hole. It's in the far west of Cravens Peak Reserve near the Northern Territory border.
A Barn Owl had been known to have been roosting there over the years, and we were keen to find as many pellets as we could. After bumping along for hours crossing the dunes and through parts of the Toomba range we got to our destination – and we were not disappointed. There was a large pile of owl-vomity goodness, each containing the mummified and undigested remains of many hapless small animals. Success for the Down-Under Chunder-Hunters!
The pellets, which numbered over 100, each seemed to contain two or three prey items – a fabulous owl-generated inventory of species around the cave.
We're in the process of sending the pellets to Dr Andrew Baker (ecologist and geneticist at Queensland University of Technology and editor of the soon to be published revised edition of Mammals of Australia). The pellets will be sorted as a student project. They will then go to Dr Heather Janetski at the Queensland Museum for final identification and lodging in the museum's collections. Stay tuned for the results later this year!
– Dr Alex Kutt, Senior Ecologist, North Region