Scientists have discovered that tarsiers, a group of tiny primates native to Southesast Asia, produce ultrasonic calls that are well beyond the audible range of humans. The frequency of the tarsirs' calls is among the most extreme of all animals, and is comparable to the ultrasonic calls made by dolphins and bats. The team of scientists, led by Nathaniel Dominy of Dartmouth, focused their study on a species of tarsier native to the Phillipines.
Tarsiers are a group of primates that diverged from monkeys and apes some 60 million years ago. The group has changed little during the past 45 million years and are considered to be living fossils. They measure a mere 5 inches from head to tail and live on a diet of small animals such as insects and reptiles.
Dominy and colleages noticed that the that tarsiers of Borneo and the Philippines were quieter than species elsewhere. This observation led them to inquire whether the vocalizations of the Borneo and Philippine tarsiers were outside the range of human hearing. They recorded sounds of 35 wild tarsiers on special equipment that captures sounds well outside the range of human hearing. They discovered that the tarsiers were producing ultrasonic calls that were otherwise similar to calls produced by tarsier species that call in the audible range. Further tests showed that tarsiers could indeed hear the ultrasonic calls.
Their findings reveal that tarsiers can both send and receive vocal signals in the ultrasonic range.
Photo © Nathaniel Dominy / Dartmouth.