The mega bat (fruit bat), contrary to its name, is not always large: the smallest species is 2.4″ long and thus smaller than some microbats. The largest have a wingspan of 5.6 ft, weighing in at up to 3.5 lbs. Most mega bats have large eyes, allowing them to orient themselves visually in twilight and inside caves and forests. Their sense of smell is excellent. Mega bats do not use echolocation with one exception, the Egyptian fruit bat Rousettus egyptiacus, which uses high-pitched tongue clicks to navigate in caves. The mega bat has been found to be carriers for a number of diseases which can prove fatal to humans and domestic animals, but the bats themselves sometimes have no signs of infection.