A small bird, about 30 cm from the tip of its beak to its tail, weighing around 220 g (about the size of an urban pigeon) has surprised researchers who recently studied it: it is the animal that makes the loudest sound among all who live on the planet – at least those on record.
These are the Amazonian spider (Procnias albus), a common species in Roraima and Pará, whose corner can reach 125 decibels (dB), slightly less than a jet plane turbine, which reaches 140 dB, but more than a rock concert (up to 120 dB), chainsaw (110 dB), drill (100 dB) and heavy traffic street (85 dB).
The discovery was made by researchers Mario Cohn-Haft of the Department of Biodiversity (COBIO) and Zoological Collections – Birds of the National Institute for Amazonian Research (Inpa), and Jeff Podos, professor of biology at the University of Massachusetts and lead author of article, published on 21/10, in the scientific journal Current Biology.
The work that led to the finding began in 2017, when Cohn-Haft collected 1,500 meters in the Serra do Apiaú in the municipality of Mucajaí, Roraima, a specimen of the Amazonian araponga for studies.
Catching the bird was part of a study of the isolated mountain and mountain fauna of the Amazon that had never been researched before.
“We wanted to have a copy of this trap to study the special characteristics of the species,” explains Cohn-Haft. “From the very crazy stuff she has hanging in her beak to the internal structures, some of which are related to the production of sounds. I was hoping to find a syringing, which is the exceptionally well-developed vocal box and part of the breathing apparatus.” but I didn’t realize she would have such extraordinary abdominal muscles.”
He said that while dissecting the collected specimen, he noted that the abdominal muscles, which in birds are usually very thin, the thickness of a sheet of paper and only used to hold the intestines, were very thick.
“The animal has a six pack,” jokes Cohn-Haft. “The Amazonian spider has wavy, well-visible abdominals that are almost one centimeter thick. It struck me. It was evident that, along with the syrinx, also differentiated in this species, it is an adaptation to produce a sound. very tall and strong without exploding the belly. ”
After realizing this, he sought out his colleague and friend Podos, who specializes in bioacoustics and dedicates his career to studying the adaptations of birds to produce different sounds and how the structure influences the song the animal can make.
“I knew he would be interested,” says Cohn-Haft. “I sent him photos of the muscles of the Amazonian spider, saying that this bird was amazing. He got excited and then we worked out a joint project, funded by the Inpa and Fulbright Foundation, that made it possible for him to come to Brazil and get us up. the saw again now earlier this year, specifically to better understand the sound of the species.”
According to him, it is very difficult to make comparisons between sound volumes of different emitters, because the measurement depends on several factors, such as distance from the source, for example.
“It is only possible to compare with the screaming of some animals, which were measured by other biologists using the same methodology and calibration that we employed,” he explains. “It is the case of the American bison (Bison bison), which reaches 107 dB, and the howler monkey (Alouatta guariba), which reaches 104 dB. Therefore, the song of the Amazonian spider is higher than that of these mammals. which is amazing because it’s so much smaller. It’s also musical so if I had to make a comparison I’d say it has about the volume of the loudest sounds of a trombone or a trumpet.”
“In addition, we want to know what this sound really is like, what adaptations, the structures that make it possible, and perhaps even more interesting to find out how the volume does not damage the hearing of the singing male or the female who listens closely. It may also have some practical application in the future, such as the development of hearing protection equipment. “