In the heart of the Amazon Rainforest, amidst the cacophony of city noise, a fascinating adaptation is taking place. Monkeys, specifically wild pied tamarins, are resorting to olfactory communication, using scent-marking almost twice as frequently when their vocal calls are swallowed by the din of human activity. This critically endangered species, which primarily inhabits patches of forest within the city of Manaus, Brazil, is demonstrating its resilience in the face of a threat that is becoming increasingly prevalent in their habitat.
"Human impacts on these animals are quite evident," says Jacob Dunn, a researcher at Anglia Ruskin University in the UK. "Right in the middle of an extremely biodiverse rainforest, there’s a massive city. The noise pollution from traffic, military exercises, and even chatty college students or crying babies is likely a significant threat to them." Dunn and his team conducted an intriguing study to understand how these monkeys alter their communication strategies in response to this auditory onslaught. The results shed light on the remarkable adaptive capabilities of these creatures, but also underscore the detrimental effects of human noise pollution on wildlife.
Amazon Monkeys Resort to Scent Messaging Amid Human Noise Pollution
Monkeys living in the Amazon Rainforest are adapting their communication styles in response to human noise pollution. Researchers have found that when their vocal calls are drowned out by traffic and other human noises, monkeys resort to sending smell-based messages nearly twice as often as usual.
The Impact of Human Noise on Animal Communication
According to Jacob Dunn at Anglia Ruskin University in the UK, the massive city in the middle of the extremely biodiverse rainforest is having obvious impacts on the animals, posing a significant threat. The study focused on wild pied tamarins (Saguinus bicolor), a critically endangered species living almost exclusively within the city of Manaus, Brazil. These monkeys communicate using vocal calls and scent-marking, where odours are rubbed onto surfaces to mark territorial boundaries and signal willingness to mate.
Study Findings: Noise Levels and Scent-Marking Behaviours
The researchers, led by Dunn, placed tracking collars on the lead female monkey in nine social groups of up to 13 pied tamarins each. Over 10 days, they tracked the groups, recording their activity and noting the noise levels in their environment. The noise in the five regions of forest where the monkeys lived ranged from 40 to 80 decibels, with an average of nearly 59 decibels.
The study revealed interesting findings. When the monkeys were in areas that reached 65 decibels, they displayed 60 per cent more scent-marking behaviour than in the quietest areas. This behaviour increased by 90 per cent when decibels reached 70 — the equivalent of a loud classroom or a running dishwasher.
The Role of Vocal Calls and Scent-marking
Interestingly, the monkeys did not use vocal calls any less often in higher decibel areas. Their calls have an average decibel level of 74 and can reach up to 89. In general, vocal calls provide quick communication over a long distance, whereas odours share information over a short distance, but for several days.
Vocal calls are used to interact not only within their own species, but also with other closely related species to regulate competition for space. If they’re unable to do that because it’s drowned out by human noise, that could potentially lead to more conflict.
While this study shows the animals’ remarkable ability to adapt, it also highlights the profound impact of human noise pollution on wildlife. Our activities are forcing these creatures to adjust their natural behaviours, which might have long-lasting effects on their survival and well-being. As we continue to encroach upon their habitats, it is crucial to understand these changes and work towards mitigating our impact on these fragile ecosystems.