Chemical camouflage for deadly snake

Puff adders – the most dangerous snake in Africa – responsible for more than 30,000 deaths every year have been found to use chemical camouflage to hunt prey and evade predators. 

This finding is the first to show a terrestrial animal using chemical camouflage known as crypsis.

Professor Graham Alexander, from the Wits University in South Africa, said: “Puff adders hunt by ambushing their prey, and can lie motionless for weeks at a single location waiting for prey to pass. This behaviour could make puff adders vulnerable to predation.

“These selective pressures have driven the evolution of not only their impressive visual camouflage, but, as we just found, also their chemical camouflage.”

The research arose after Professor Alexander noticed puff adders lie still when threatened and position themselves under vegetation instead of burrowing underground.  Additionally dogs and mongooses, animals with a keen sense of smell, are known to walk over motionless puff adders unaware of their position.

For this study a team of students trained dogs and meerkats to investigate if they could detect the puff adders scent. Ashadee Kay-Miller, a postgraduate student at Wits, said: “We asked the meerkats and dogs to scent-match scent samples collected from puff adders and other snake species. The scents of most snakes were easily identified by the dogs and meerkats, but they failed dismally when it came to puff adder scent.”

Theories for how the snakes camouflage themselves include the snakes possessing a slow metabolism to maintain their odour levels beneath a certain threshold. The micro ornamentation of their scales may also be involved.                                                                                                                                                                                                                                                                                                                                                                                                      However, the research team believe chemical crypsis is common among ambushing species but as smell is not the primary sense used by humans it has not been a focus for research.

The findings were published in Royal Society Proceedings B