The study was conducted by researchers from the University of the Witwatersrand’s Plant and Environmental Sciences department.
“… Selective pressures have driven the evolution of, not only their impressive visual camouflage but, as we have just found, also their chemical camouflage,” Professor Graham Alexander, head of the Alexander Herp Laboratory at Wits said.
The study has shown that the African viper species not only camouflage themselves with their highly evolved visual camouflage, but they are also difficult to find by smell. The research is the first to show a terrestrial animal using chemical crypsis, or chemical camouflage, in order to survive.
According to Alexander, puff adders hunt by ambushing their prey, and can lie motionless for weeks at a single location waiting for prey to pass. This behaviour makes them vulnerable to predation.
During an intensive three-year telemetry project that involved the radio-tracking of 30 puff adders, three lines of evidence led Alexander to conclude that they must also possess a form of chemical camouflage.
The study depicted that, firstly, puff adders usually remain motionless when under threat and, secondly, spend most of their time under grass or other vegetation and do not often seek refuge underground, as is usual for most other snakes. This would make them easy targets for predators if they had a strong scent. Thirdly, they observed that dogs, and the tame mongooses used in the study, walked directly over motionless puff adders with both predators appearing to be completely unaware of the motionless snakes.
The study further depicted that of the 42 known predators of puff adders, 15, including dogs and meerkats, relied primarily on their keen sense of smell to locate their prey. A team led by Wits post-graduate student Ashadee Miller investigated this question by training a team of dogs, and meerkats from the Bird Gardens, to scent-match and test if they could detect the scent of puff adders.
“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 the puff adder scent,” Miller said.
While the puff adder is the first terrestrial vertebrate species for which chemical crypsis has been demonstrated, the researchers believe that this phenomenon is likely to be common among many ambushing species. However, because the capacity of smell is not the primary sense used by humans, not much research has focused on this aspect of biology.
Curator of reptiles for the Bird Gardens, Chris Cooke said, “We, at Montecasino Bird Gardens, are very proud to be involved with this research project. We feel that zoos like ourselves can really contribute to science and conservation, and we hope that by discovering more about these greatly misunderstood animals such as puff adders, we can ultimately help conserve and protect them.
“Our meerkats really enjoyed their training. It was excellent enrichment for them. They really had to use their problem-solving skills during the trials.”
