Croaking science is a new way for student volunteers and scientist to explore what’s occurring in the world of Science. Croaking Science looks at science facts, new research or old debates which are inspired by or affect amphibians and reptiles, and then communicates this in layman’s language to a wider audience. The aim of the feature is to provide a platform for those starting their foray into the world of science communications as well as established scientists. We welcome any submissions from students and scientists. Please note that the views expressed in the articles are not those of the Froglife Trust
Hannah Graves finds out about what it can take to survive the school of hard knocks in the animal kingdom.
With their soft skin and small size, amphibians are an obvious target for predators. This has lead to the evolution of a huge variety of self-defence mechanisms. These include some of the more commonplace such as camouflage and poison, but also some truly bizarre methods (1).
In Central Africa 11 species of frog have been found to have concealed weapons (2) in their feet! The frogs appear to have feet just like those of any other amphibian, until they are threatened. At this point claws appear that are sharp enough to draw blood, even from humans. But these claws aren’t simply hidden away in specialised structures like in cats. The claws are actually razor-sharp bones in the toes, and the frogs have to puncture their own skin to use them! (3).
The sharp-ribbed salamander has taken this method one step further. As the name suggests, their sharp bones are ribs instead of toes. When they are attacked a line of spines appear down the sides of their body. As the sharp bones protrude, the salamander also secretes a poisonous substance onto their skin. So the sharp points almost inject poison into the predator, causing maximum pain (4). The salamander also appears to be immune to its own poison, which seeps through its own wounds and doesn’t seem to cause the salamander any problems (4).
In both of these cases the frog and the salamander have been shown to puncture their skin each time they use this emergency tactic rather than having the bones extrude through a pre-determined pore. The salamander achieves this by bringing its ribs forwards and stretching the skin to the point of puncture (4). The frogs have tiny bones at the tips of their toes that keep the skin in place when these are flexed; the skin around the “claw” bones becomes stretched taut allowing the bones to puncture through (3). After use, the “claws” relax back into their original position. Amphibians are known to have regenerative abilities, and it is thought that this allows these species to repair their skin and survive these self-inflicted injuries (4).
Further research is planned to establish how the bones retract into the body and exactly how the skin regenerates (3). It is also hoped that the compounds making up the poison in the salamander will be investigated (5).
Want to know more cool facts?
Check out Froglife’s species pages for more information on our native species.
Grass snakes can fake self injuries and play dead – to the point of extruding a bit of their gut outside of their body! If you see any weird and wonderful ways used by reptiles and amphibians to repel predators why not take a photograph and send it in to Froglife, where the best ones will be shared online.
Report any of your UK amphibian or reptile sightings using our Dragon Finder App and share your memories with us.
1. Pough, F.H.; Andrews, R.M.; Cadle, J.E.; Crump, M.L.; Savitzky, A.H.; Wells, K.D. (2001) Herpetology 2nd Ed. Prentice Hall Inc., New Jersey.
2. Bradt, S. (2008) When threatened, a few African frogs can morph toes into claws. [Accessed 02/01/14]
3. Blackburn, D.C.; Hanken, J.; Jenkins, F.A. (2008) Concealed weapons: erectile claws in African frogs. Biology Letters 4:355–357.
4. Heiss, E.; Natchev, N.; Salaberger, D.; Gumpenberger, M.; Rabanser, A.; Weisgram, J. (2009). Hurt yourself to hurt your enemy: new insights on the function of the bizarre antipredator mechanism in the salamandrid Pleurodeles waltl. Journal of Zoology doi:10.1111/j.1469-7998.2009.00631.x.
5. Walker, M. (2009) Bizarre newt uses ribs as weapons. [Accessed 02/01/14].