African Clawed Frog (Xenopus laevis)

I don’t usually picture frogs with clawed feet — I’m much more familiar with the typical webbed foot with sticky balled toes on the end. Today’s animal is one of those special frogs that decided to forego the expectations of frog society and grow claws on its feet. How exciting!

African clawed frogs are naturally found in Africa ( a big shocker, I know), particularly in the southern part of the continent. They have been introduced to a number of other places, including California, Chile, and Great Britain. These frogs favour habitats that are warm, stagnant, and covered in algae — in other words, places that are disgusting. Not only do clawed frogs like to live in these tepid, horrifying waters, but they rarely leave them, only exiting their chosen ponds when forced to migrate.

A nice picture of a clawed frog showing the claws on its back feet.  Image source: http://www.clawedfrogs.com/

A nice picture of a clawed frog showing the claws on its back feet.
Image source: http://www.clawedfrogs.com/

Though they are called clawed frogs, the claws on their feet are not the only weird thing about these frogs. They don’t have tongues, so you can also throw out the classic image of a frog happily catching insects with its long tongue. Another thing clawed frogs lack is external ears. Males grow to be about five centimetres long, while females can reach ten to twelve centimetres.  Clawed frogs have very smooth skin (the second part of their latin name, laevis, means smooth). Their front feet have no webbing, and while the back feet are webbed, they also posses the weird claws for which this animal is named, with each of the three inner toes being clawed.

These claws help the frogs feed. Clawed frogs are scavengers, eating anything that crosses their paths. If their potential meal is too big, the frogs will use their claws to rip it apart into appropriate sizes. Clawed frogs use a number of senses to detect scraps of food: their front ‘fingers’ are very sensitive; they have a very good sense of smell; and they possess a lateral line system (used to detect movement and vibrations in the water), something that is usually only found in fish.

Some African clawed frogs hanging out. Image credit: Tim Vickers

Some African clawed frogs hanging out.
Image credit: Tim Vickers

Mating in clawed frogs usually occurs in spring, but can occur at any time of the year. Males call out to females, advertising their readiness to mate. Females will then call back, using either a rapping sound for acceptance, or a slow ticking which signals rejection of the male. This behaviour of replying to a male’s call is extremely rare in the animal kingdom.

Living in arid and semi-arid conditions means that clawed frogs face the constant threat of having their homes dry up. Luckily these guys are very resilient. If their ponds dry up they will burrow underground, leaving themselves a small air hole, and stay dormant for up to a year. If things get really bad during the rainy season, the frogs will migrate, sometimes travelling long distances, surviving thanks to rain. This is quite the ordeal for the frogs, because although they are very capable swimmers, they can’t hop on land, instead crawling their way around.

The hardiness and resilience of  this frog means that it is doing quite well. It has been used in research to investigate embryonic development and to develop pregnancy tests. Once better pregnancy tests were developed, many clawed frogs were released into the wild, leading to their colonization of many areas outside Africa. Responsible science, everyone!

Cover image source: http://www.clawedfrogs.com/

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