The Tiny, Ultrasonic Philippine Tarsier (Video)

Tarsiers are among the world’s smallest primates. Only five inches tall, with big eyes and ears, some species from Borneo and the Philippines have been thought to be silent, though other species have calls that are audible to humans and used for sending out alarms about danger, or for social interactions. Researchers from Dartmouth University have now found that Tarsius syrichta, one tarsier species in the Philippines, uses ultrasonic vocalizations to communicate. Anthropology professor Nathaniel Dominy studied the Philippine tarsier’s hearing and vocalizations and describes their way of communicating as “extreme, and comparable to the highly specialized vocalizations of bats and dolphins, which are used primarily for echolocation.”

Dominy and other researchers suspected that the Philippine Tarsier did have some form of communication, as do the other species. Recent technical advances helped them to study tarsiers’ communication:

They found “an audible range that extended substantially into the ultrasound,” reaching a high of 91 kilohertz (kHz), “a value that surpasses the known range of all other primates and is matched by few animals.”

They also used a microphone and recording unit capable of registering sounds up 96 kHz. The upper limit of human hearing is generally set at 20 kHz, and frequencies above this limit are classified as ultrasound. In the field, the team recorded the sounds of 35 wild tarsiers from the islands of Bohol and Leyte with this equipment, documenting eight individuals giving out a purely ultrasonic call at approximately 70 kHz. The tone-like structure of the call resembles those of other tarsier species, but none were purely ultrasonic.

Noting that the tarsiers issued their ultrasonic calls when humans were near, the researchers speculated that they were voicing alarm.

In fact, Dominy and his colleagues suggest that “there may be selective advantages to vocalizations in the pure ultrasound” as these provide “private channels of communication with the potential to subvert detection by predators, prey, and competitors.” Tarsiers dine exclusively on insects such as moths and katydids, which emit sounds in ultrahigh frequencies. As Daniel Strain writes in Science, “because tarsiers’ perky ears are so sensitive, they may be able to intercept this chatter at night—then zoom in for the kill.”

In addition, because tarsiers’ “nails-on-a-chalkboard trills” are too high-pitched for predators such as birds to hear, their ultrasonic vocalizations make it possible to communicate without being noticed. Silence, or what seems like silence to most ears, can indeed be golden.

The researchers’ findings has been published in the Royal Society journal Biology Letters.

Related Care2 Coverage

“Extinct” Monkey Rediscovered in Borneo Rainforest

Over 100 Dolphins Stranded in Cape Cod: Why?

Ape, All Too Human

Photo by Roberto Verso

Disclaimer: The views expressed above are solely those of the author and may not reflect those of
Care2, Inc., its employees or advertisers.

Eternal G.

3:40PM PST on Mar 5, 2012

Please protect them from extinction!

send a green star

Nancy L.

8:36PM PST on Feb 16, 2012

Very cute creature!!

Kathy P.

8:34AM PST on Feb 16, 2012

they are so darn cute

Stefanie D.

3:15PM PST on Feb 15, 2012

Although we humans don't use ultrasonic vocalizations specifically, we're probably capable of it incidentally, as well as whistling, or doing the hissing and 'ffff', 'ssss', 'shhh', 'chhh', and 'thhh', and 'whhh' types of 'white' noise. I'd love to know how much of our own articulated 'white noise' sounds are in the ultrasonic range unbeknownst to ourselves (beyond what we do hear), and how much of it animals that can hear in those ultrasonic ranges respond to or not.

Barbara H.

2:02PM PST on Feb 15, 2012

COOL!

Penny C.

10:50PM PST on Feb 13, 2012

Thanks.

stacy m.

10:08PM PST on Feb 13, 2012

aww....they're so cute

Melanie M.

9:07PM PST on Feb 13, 2012

They are cute, although I live in the Philippines, I haven't see this wonderful creature, they are miles and miles away from home. Wish I could visit Bohol.

Mara C.

9:01PM PST on Feb 13, 2012

I saw a recent video, on Care 2, about the Tarsier. The Philippino guide explained that when these little monkeys become stressed, they commit suicide! The constant parade of tourists, marching through the Tarsier's natural habitat, is very stressful for them. I read that they also commit suicide when in captivity (zoos).