Image: © mgkuijpers/Stock.adobe.com
Researchers have discovered that a type of African toad has developed the ability to disguise itself as a deadly viper in both looks and behaviour.
The chameleon is perhaps the most famous creature to drastically alter its appearance for camouflage, but researchers from the University of Texas at El Paso have discovered another creature that goes even further to avoid being a predator’s dinner.
They have shown how the Congolese giant toad can closely mimic one of Africa’s largest vipers not only in appearance, but how it behaves. The Gaboon viper, which the toad mimics, has the longest snake fangs in the world and produces more venom than any other snake.
The study published to the Journal of Natural History is based on 10 years of fieldwork and direct observations of the toad species and has described its behaviour as Batesian mimicry, where a harmless species avoids predators by pretending to be a dangerous or toxic one.
To fully test this hypothesis, the researchers said that they would need to prove that predators were duped into thinking it was a Gaboon viper, which they admit would be very difficult in the wild. However, based on multiple sources of evidence laid out in the study, they said they were confident of confirming it.
Side-by-side comparison between a subadult toad and subadult Gaboon viper from an aerial perspective. Image: Colin Tilbury
Toad with a threatening hiss
Key to the Congolese giant toad’s ability to mimic the viper is the fact its body is of a similar shape to snake’s head, due in part to how it looks but also the species’ extraordinarily smooth skin unlike most toads.
Aside from its striking visual similarity, the toad can also closely resemble the viper in its threatened state. When the viper fears it is about to be attacked, it will often incline its head and emit a long, loud warning hiss before it actually makes a strike.
Incredibly, one researcher observed the toad emitting a similar hissing noise resembling the sound of air being released from a balloon. Over a century ago, a bow display by the toad was seen for the first time, where the front limbs no longer prop up the viperine-shaped body, which looks similar to the cocked head of a snake threatening to strike.
Adding further to the researchers’ hypothesis, the Congolese giant toad and Gaboon viper evolved around the same time about 4m to 5m years ago.
“Because the viper is deadly venomous, they probably recognise the distinctive, contrasting markings from a considerable distance and avoid the toad because of them, receiving a threatening hiss if the appearance doesn’t put them off,” said Congolese herpetologist Chifundera Kusamba.
