We think of communication being loud and obvious; body language and vocalisations - animals doing everything they can to be seen and heard - but there is a whole other world of signals that is invisible to us. Animals use colours that we can’t see, and scents too subtle for us to even notice, and yet for their own kind, these cues speak volumes.

Technology can help us to crack the code, and might even prove a valuable tool to protect endangered species. Dr. Stefano Vaglio specialises in unravelling the hidden world of primate olfactory communication. He is analysing the secret messages of captive primates, and discovering a wealth of information about sex, age, health, social status and reproductive cycle. Can he use his discoveries to help in primate conservation? Scent is a common form of communication across the animal kingdom. Solitary animals, like bears, still need to have some sense of their neighbours, giving vital information about mating opportunities and interlopers in their range. Sniffing where other bears have been is like reading the morning newspaper. Dr. Rachel Sawyers is working on bottling the lemur ‘love potion’. She’s analysing the chemical signature a female lemur in oestrus leaves behind, to see if she can trigger stink flirting from the alpha male of another troop. But scent is not the only messaging that’s invisible to us going on in the natural world. A German biologist, quite by chance, discovered that some of his chameleon specimens’ skeletons glow under Ultraviolet light, and this can be seen through their skin. He believes it’s used not only as a sexual display, but a social one too, helping the animals to organise a social hierarchy. Could what scientists are now learning about these invisible languages provide a lifeline to save some of our most endangered species?