Crested gibbons of the genus Nomascus are small apes that live in the dense rainforests of Cambodia, China, Laos and Vietnam. All seven species communicate by singing—they sing to define their territory and find a mate, and male-female pairs sing duets to strengthen their bond, rather like a Bollywood couple.
They're not all singing the same song, though, say researchers from the German Primate Center in Goettingen. The scientists analyzed the acoustic structure of 92 gibbon duets from 24 locations in Cambodia, Laos and Vietnam, covering six of the seven species, and compared mitochondrial DNA from gibbons at 22 of the 24 locations. They report their findings in BMC Evolutionary Biology.
The researchers found that the songs of the two northern species, N. nasutus and N. concolor, were significantly different from those of the four southern species, and the songs of the four southern species were all subtly different from one another. And the more closely related two species or populations songs were, the more alike was their mitochondrial DNA.
"Each gibbon has its own variable song but, much like people, there is a regional similarity between gibbons within the same location," says lead researcher Van Ngoc Thinh.
These regional differences can be best compared to regional dialects in human speech, but that's were the comparisons to us should probably end. The researchers say that gibbon vocalizations more closely resemble those of rainforest birds in both sound and purpose.