expression, suru verb (irregular)
prick up one's ears; listen attentively
Idiomatic expression meaning to listen very carefully, as if making one's ears as big as Dumbo's. Often used when trying to catch faint or distant sounds.
See also: 耳がダンボ (みみがダンボ)
隣の部屋の話が気になって、耳をダンボにした。
Curious about the conversation in the next room, I pricked up my ears.
赤ちゃんが泣いていないか、耳をダンボにして聞いていた。
I was listening attentively, straining my ears to hear if the baby was crying.