New Macaulay Library clips let you listen to gibbons hoot in Thailand’s forests

The Cornell Lab’s Macaulay Library is the world’s largest and oldest archive of natural sounds and video, and you can browse its holdings online. Though it’s best known for its bird recordings, the Macaulay Library also features insects, fish, amphibians, reptiles, and mammals—including a recent addition: gibbons recorded in the wild in Thailand. They’re the work of Warren Brockelman, who spent years studying the apes and recently added his recordings to the archive.

“The beautiful movements of gibbons in the trees and their incredible songs whetted my appetite for studying them in the wild,” recalled ecologist Warren Brockelman (B.A. Cornell ’63; at left). Brockelman first encountered gibbons while working for the army in a Bangkok field laboratory during the Vietnam War. After the war he settled in Thailand (his wife is a Thai zoologist) and in 1976 began doing gibbon research in the Khao Yai National Park, a large reserve about three hours northeast of Bangkok. He concentrated on two species in particular, the white-handed gibbon (Hylobates lar) and the endangered pileated gibbon (Hylobates pileatus).

As he worked in the jungle, Brockelman was entranced by the duets of the gibbons, their voices falling, rising, and carrying for more than a mile. Then he got close enough with his trusty reel-to-reel Nagra SN recorder (first developed for spy agencies and the film industry) to pick up the softer sounds that other recordists had missed. “One thing that gibbons ‘talk’ about is threats,” Brockelman says, “When I heard a soft, barely audible hu-hu-hu-hu above me it meant that the male had detected me below, and the group immediately stopped what it was doing.” There are about 10-15 distinct sounds in the gibbon “vocabulary.”

Even when they sing together, mated male and female gibbons don’t sing the same song. The distinctive female part is the “great call,” a series of hoots lasting 15 to 20 seconds. “One of my most important findings was that young gibbons do not learn to sing the species-specific patterns of their duets, but the patterns are rather strictly inherited,” Brockelman explains. “They appear to have no attributes of language as it is defined for humans. They are rigid and stereotyped, like bird song—even more so because some birds can learn new phrases.” Females usually initiate the duet with a quiet hua-hua sound. Brockelman and his colleagues also brought much new information to light about gibbon society, including how slowly populations grow—a mated pair produces a single offspring only once every three years.

Even working in an environment populated with wild elephants, cobras, tree vipers, pythons, bears, and (at that time) tigers, Brockelman says the biggest scare came from his own species. Half a dozen insurgents once held him at gunpoint with AK-47 rifles. He managed to talk them into letting him go. “Wild animals are much more predictable,” says Brockelman.

When Brockelman decided it was time to preserve his recordings, he turned to the Macaulay Library. He worked with archivist David McCartt to preserve his written data and turn the analog recordings into digital files. Because the tapes were stored for more than 30 years, sometimes in damp conditions, the process was more complicated than you might expect. Macaulay Library engineer Karl Fiske jury-rigged a device that meant hand-winding the old tapes past Q-tips to clean the tapes. But it worked like a charm, and about half the recordings have been digitized. Brockelman expects to visit again next year to archive the rest.

“Warren kept very organized records,” says McCartt. “I think he’s like a lot of researchers who are now looking for a place where they can permanently archive their work and know it will be well cared for and available to everyone.”

Listen to a few of Brockelman’s gibbon recordings:

• White-handed gibbon 1 (male and female duet; 1980)
• White-handed gibbon 2 (male and female duet; 1980)
• Pileated gibbon (male and female duet, with young female joining in; 1980)