When their vocal calls get drowned out by traffic and other human noises, monkeys living in the Amazon Rainforest resort to sending smell-based messages nearly twice as often as usual.

“Right in the middle of the Amazon Rainforest, you’ve got an extremely biodiverse rainforest with a massive city in the middle of it,” says Jacob Dunn at Anglia Ruskin University in the UK. “So human impacts are quite obvious on these animals, and it’s likely to be quite an important threat to them.”

Wild pied tamarins (Saguinus bicolor) – a critically endangered species living almost exclusively in patches of forest within the city of Manaus, Brazil – communicate with both vocal calls and scent-marking, in which they rub odours onto surfaces to mark their territorial boundaries and signal willingness to mate. 

Read more: newscientist.com

Photo: newscientist.com