Echolocation follows
Within a few million years bats are broadcasting ultrasound and listening to the echoes.
- When
- —
- Duration
- 4 million years
- Known to
- ± 1 million years
- Era
- Eocene, Cenozoic
Icaronycteris and other early Eocene bats already show the enlarged cochlea and robust stylohyal that indicate laryngeal echolocation, so the capability appears close behind flight itself. It opens the night sky: flying insects at night are an enormous, essentially unexploited food supply, and no bird can take it. The arms race that follows leaves marks on both sides — moths evolve ultrasound-sensitive ears and jamming clicks, and some bats shift their calls out of the frequencies moths hear best.