National Geographic : 1950 Apr
Voices of the Night An Explorer with Microphone and Flashlight Finds in Jungle and Roadside Ponds Unexpected Beauty and Interest BY ARTHUR A. ALLEN Professor of Ornithology at Cornell University With Illustrations from Photographs by the Author " HERE is some strange animal that sneaks through the jungle and watches us at work," said Dr. Eyring. "We hear the twigs snapping as it approaches, but it never comes close enough for us to see it. "Each morning, when we are setting up our instruments, and again off and on during the day we hear it; but we have no idea how large it is. Perhaps it is a jaguar, perhaps only a curious native; but it gives us an eerie feeling to know we are being watched. Possibly you and Dr. Kellogg can identify and record it." This was exactly the sort of problem that had brought us the invitation to join the Office of Scientific Research and Development proj ect on jungle acoustics, and had taken us to Panama on the first leg of an expedition bound for the South Seas. The engineers and physicists under Dr. Carl F. Eyring were assigned the job of measuring what happens to sound under all sorts of jungle conditions, and Dr. Paul Kellogg, associate professor of ornithology at Cornell, my son David, and I were responsible for recording and identifying the natural sounds that ema nate from the jungle. Here was our first challenge. For several weeks we had been recording the songs and calls of birds by day and the squeals and whistles and groans of all kinds of animals at night. Recording bird voices was an old story to us, for we had been doing it in the States for years;* but to sneak through the jungle at night with a flashlight and a micro phone was a different experience. We had come to appreciate how our boys in New Guinea felt when they were encamped in the jungle and had to listen to the strange sounds which, for aught they knew, were ema nating from Japs as often as from animals. Their experiences gave birth to the OSRD project upon which we were engaged. The next day found us near Madden Field, in Panama, in response to Dr. Eyring's sug gestion, where the engineers had cleared a long, narrow strip through the jungle and set up their instruments at either end. Kellogg and I scoured the area for animal signs and then sat down to listen. In half an hour twigs began to crackle, and we could well have imagined an enemy sneaking up on us. I had taken my stand against a tree close to a tiny clearing and then, as the crackling sounds grew louder, I could see a small black-and-orange bird flitting from the side of one sapling to another close to the ground across the open space. Sounds of a Courtship Dance What Dr. Eyring had heard was the court ship dance of Gould's manakin. The twig snapping sound was made with the bird's swollen wing quills rubbing against each other as it flitted from one small tree to the next. This curious performance is described in Frank M. Chapman's book, Life in an Air Castle. Not all of the jungle sounds were so easily identified. Some of the small birds, such as the green shrike vireos, that sang loudly from the lofty canopy of the jungle, though well recorded, remained unidentified for weeks. Some of the night sounds remain unknown to us even today, because we were unable to catch the insects that perpetrated them. Many of the more satisfactory sounds were made by the tailless amphibians-i.e., frogs, toads, and tree frogs (page 514). They were satisfactory in that they could be tracked down with a flashlight, and the creatures didn't mind continuing their concerts in the beam of the light until they were captured.t Even so, there were many surprises, such as the "cave frogs," which sang from little bur rows in the mud at the edge of a pond and could not be found even when the flashlight was only inches from them. One narrow-mouthed toad (Engystomops pustulosus) sounded like a large animal in distress; but when we found him calling by a little pool in the jungle, he was scarcely an inch long and round as a marble. * See, in the NATIONAL GEOGRAPHIC MAGAZINE: "Touring for Birds with Microphone and Color Cameras," June, 1944, and "Hunting with a Micro phone the Voices of Vanishing Birds," June, 1937, both by Dr. Allen. t See "A Frog That Eats Bats and Snakes (Smoky Jungle Frog)," by Kenneth W. Vinton, NATIONAL GEOGRAPHIC MAGAZINE, May, 1938.