World's Highest-Pitched Primate Calls Out Like a Bat

A huge-eyed little primate of the Philippines can communicate in pure ultrasound — issuing calls so high-pitched that human ears can't detect them.

Study researcher Marissa Ramsier noted the ironic discovery in an animal that has always been considered a quiet night creature. "It turns out that it's not silent. It's actually screaming and we had no idea," said Ramsier, an evolutionary biologist at Humboldt State University in California.

The shrillest noise a human can hear has a frequency of about 20 kilohertz. The Philippine tarsier can hear up to 91 kilohertz, and it cries out in the 70-kHz range. Those numbers put the tarsier's hearing abilities in the same range as bats and far beyond those of any other primate ever known.

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