Acoustic prey and a listening predator: interaction between calling katydids and the bat-eared fox

Abstract

The bat-eared fox is an insectivorous, nocturnal predator that uses its characteristic large ears to detect sounds made by invertebrate prey. Behavioural observations of the bat-eared fox emphasize the significant role hearing plays in insect prey detection and localization. In turn, katydids are nocturnal insects that risk attracting predators by producing conspicuous signals for mate attraction and pair formation. To determine the interaction and potential level of predation between this listening, insectivorous predator with acoustically active katydids, behavioural observations and scat collection from bat-eared fox individuals were conducted in the Western Cape, South Africa. Acoustic surveys were also conducted to identify acoustic species within foraging areas of bat-eared foxes and assist with identifying their remains in scat. Results indicated that bat-eared foxes have a broad, opportunistic diet. Despite the fox's hearing ability, and its use of sound to detect insect prey, acoustically active species were not consumed as part of the bat-eared fox diet. Instead, acoustically mute invertebrates such as most beetles and cockroaches were the dominant prey, followed by fruit and vertebrate prey, such as lizards, small mammals and nestlings. Although there was a diverse acoustic assemblage of katydids across the landscape, their absence within the bat-eared fox diet may either reflect a preference for other prey, or suggests highly developed anti-predator behaviour found within this insect group in which predation pressure has been a major evolutionary driver. It is likely that both apply, and currently bat-eared foxes find foraging on other prey more optimal.