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Cryptic clue in evolutionary puzzle

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Can a dog smell a puff adder? If not, why not?

Zoologist Ashadee Miller (BSc 2007; BSc Hons 2008, MSc 2016) was part of a team that conducted research into the chemical camouflage of snakes.

They found that trained dogs and meerkats could detect the scent of snake species that actively hunt for their prey, but did not pick up any scent from puff adders, which hide and ambush their prey.

So, not only are these common, venomous snakes hard to spot in the veld, but your scent-sniffing canine companion won’t help you avoid them either.

The researchers think this is the first proof of a vertebrate avoiding detection by hiding its scent, but it’s likely to be a widespread defence. “It makes perfect evolutionary sense for chemical camouflage to evolve as frequently as visual camouflage has, when there are many predator species that rely on scent to locate their prey, just as there are many that rely on vision,” says Ashadee.

Adapt or die                                             

Ashadee says scent research is “quite a novel field” and has a lot of potential. She is working on her PhD at the moment, “trying to elucidate the mechanism driving the puff adder’s chemical crypsis or scentlessness”. The theme of her work lies in the idea of “evolutionary warfare between predator and prey species, where there is this continuum of one trying to ‘outgun’ the other. It is in these situations of high selective pressures, such as the one the puff adder finds itself in because of its many predator species, where we are likely to find the most impressive evolutionary adaptations.

“Before we demonstrated chemical crypsis in the puff adder, the idea that a living, breathing organism could be scentless was thought impossible. This is simply because byproducts associated with metabolism (such as carbon dioxide and acetone) are typically odorous, but now that we’ve shown that it is a reality in one species (and probably many others) we need to understand how it’s done, and we think it’s something very exciting.”

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