Natures wonders: toad mimics viper head (Introduction)

by David Turell , Tuesday, October 22, 2019, 02:03 (1858 days ago) @ David Turell

One must wonder how the toad did this, all by itself:

https://cosmosmagazine.com/biology/meet-the-cunning-toad-viper?utm_source=Cosmos+-+Mast...

"Results published in the Journal of Natural History reveal that the hamburger-sized Congolese giant toad (Sclerophrys channingi) likely imitates the formidable Gaboon viper (Bitis gabonica) in both appearance and behaviour.

"At an average length in the 125-155 centimetre range, B. gabonica is one of Africa’s largest vipers. It has the longest fangs, reaching up to five centimetres, and highest yield of venom – although not especially toxic – of any known snake.

"A research team led by Eli Greenbaum, from the University of Texas at El Paso, US, believes S. channingi may use its ability to mimic B. gabonica to escape predation.

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"...based on multiple sources of evidence provided in our study, we are confident that our mimicry hypothesis is well-supported,” Greenbaum says.

"The researchers compared the appearance of the toad, found in central African rainforests, and the viper, which is more widely distributed in central, eastern and southern Africa.
Using live wild-caught and captive individuals, and preserved museum specimens, they found that the colour pattern and shape of the toad’s body is similar to that of the viper’s head.

"Most striking are two dark brown spots and a dark brown stripe that extends down the toad’s back, the triangular shape of its body, a sharp demarcation between its tan back and dark brown flanks, and the species’ extraordinarily smooth skin for a toad.

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"Gaboon vipers are renowned for their placidity – it’s said that humans must literally step on the snake to prompt a bite – and even then it’s not guaranteed; if an individual feels threatened, it will often incline its head and emit a long, loud warning hiss before resorting to a strike.

"Similarly, herpetologist Chifundera Kusamba, from the Centre de Recherche en Sciences Naturelles in the Democratic Republic of Congo (DRC), observed the toad emitting a hissing noise resembling the sound of air being slowly released from a balloon. And over a century ago, US biologist James Chapin observed the toad "bow" – lowering its front limbs so they no longer propped up the viperine-shaped body, which made it look similar to the cocked head of a snake threatening to strike.

"The last part of a successful impersonation is location. Even the best mimickry will only work if predators of the harmless species are familiar with the venomous one.
The researchers compared the geographical range of the toad and viper in the DRC and found that S. channingi does not seem to occur in areas where B. gabonica is absent. The researchers identified 11 locations in the eastern rainforests where the range of both species overlaps."

Comment: this must require several specialized mutations. I think the toad was helped. For side by side pictures look at this website:

https://www.sciencemag.org/news/2019/10/one-these-deadly-viper-other-harmless-toad-can-...