The Philippine tarsier (Tarsius syrichta), a 5-inch tall Southeast Asian primate, has long resembled a ventriloquist's doll. It would open its mouth as though chattering away, but researchers heard nothing. Now, a study in Biology Letters has found out why: the Philippine tarsier communicates ultrasonically, surpassing all other primates, and nearly all terrestrial mammals, in its ability to create sounds in the upper registry.