Mice often communicate in ultrasound, which is so high-pitched that it's beyond human hearing. Because these sounds don't travel very far, it was thought that they were only used for private, close-up conversations. New research on wild African striped mice (Rhabdomys pumilio) reveals a clever way these rodents use their "private" calls for "public" messages, extending the reach of short-range signals. They do this by switching to a specific type of call when they are at the borders of their territories.