Faunal studies in the Riversleigh/Boodjamulla area of north-western Queensland undertaken between 1990 and 2011 revealed a decline in the number of Ghost Bats Macroderma gigas. Cane Toads Rhinella marina reached Boodjamulla in 1986 and were widespread by 1988. The last reported sighting of a Ghost Bat in Boodjamulla was in 1993.
In view of the absence of sightings, an extensive targeted survey for Ghost Bats was initiated in 2012 in the Riversleigh World Heritage Area and elsewhere in the Boodjamulla National Park (NP). No Ghost Bats were found in historic roosting sites. Helicopter surveys located another 24 potential Ghost Bat sites but none contained evidence of occupation by these carnivorous bats. A number of cave features that were considered to be important to Ghost Bats and Cane Toads were recorded and samples of Ghost Bat droppings were collected from the cave floor. All of the historic roosting caves contained water and were inhabited by Cane Toads.
In 2013, the search for Ghost bats was extended to the Camooweal Caves NP, the nearest known Ghost Bat colony to Riversleigh/Boodjamulla. Ghost Bats were found in seven caves in the Camooweal Caves NP. Again, cave features were recorded and cave floor samples taken. Cane Toads were not present in any of the caves at Camooweal Caves NP despite being present in the local area.
In 2013/2014, Ghost Bat surveys were extended to Kakadu NP in the Northern Territory. Many historically occupied roost sites were found to be devoid of Ghost Bats, but some more remote caves still retained extant populations (albeit in low numbers). Cave floor samples of droppings revealed that toads were being taken as a very minor component of the vertebrate prey of Ghost Bats. One dead Ghost Bat was found with a partly masticated toad in its oesophagus. This, and other indirect evidence, indicates that Cane Toads are being taken by Ghost Bats on an occasional basis and that these episodic predation events may be a significant factor in the observed decline in Ghost Bats populations in areas where Cane Toads are abundant.
