Predation upon moths by free-foraging Hipposideros caffer

Predation upon insects by the bat Hipposideros caffer was studied at Skukuza in the Kruger National Park of South Africa. These bats, whose echolocation calls are inaudible to moths, fed overwhelmingly upon tympanate Lepidoptera, although insects of other orders frequently dominated the local light-responsive, flying, nocturnal insect community. The relative numbers of noctuid, pyralid, and arctiid moths taken by the bats were proportional to the representation of these families in the general population of moths, but they took disproportionately fewer moths of the family Geometridae. The bats also ate significantly fewer arctiid moths of those species capable of clicking than of those species that could not. Because the arctiids could nor hear approaching H. caffer, these moths did not click before contact with an attacking bat, and their clicks could not protect them by interfering with echolocation by the predators. These results are consistent with the startle and acoustic-aposematism hypotheses for the bat-protective function of arctiid clicks.