When we look at the tadpole we can see that indeed the tail makes for an excellent way to move the young amphibian forward, in fact it is the only way they can move. We need to look at the way the adult moves to understand the absence of a frog tail –basically it would get in the way of the leaping motion that the frog uses to move across the land.

Of course most species of frog are also partially aquatic, so one might think that a frog would find a tail useful for swimming in the same way as fish use their tails to propel them forward. However, frogs swim in a breaststroke-like style that is quite different from other animals that take to the water, and the tail is not needed even in frogs that do not venture out of water.

At first glance it seems that because of the way frogs move on land they have no tail, and because they have no tail they had to develop an innovative aquatic movement, but we cannot conclusively say that is accurate.

Just what is it about the frog that made it evolve in such a different way to other animals with backbones?

One theory of the development of frog movement relates to the fact that some species of frog burrow (but in typical frog-like fashion they don’t burrow forwards, but backwards!) Being able to retreat backwards allows the frog to hide from predators, and gives it the element of surprise when it sights some prey. All frogs have an extra bone on the front of their first toes, and this is useful in backwards burrowing. Thus whilst only a few species of frog burrow backwards today, this extra toe bone points to the fact that such burrowing may have been the norm years ago, and a tail would certainly get in the way of such backwards movement. This is just a theory on the frog tail, and there is no consensus that this burrowing characteristic played such a major evolutionary role. In fact there is no agreement even on why frogs leap.

Some say that frogs evolved to leap in order to quickly seize prey when in the water, and as they evolved to make the move on land they just kept this movement. The other school of thought is that frogs only started to leap as a way to move quickly on land – proponents of this theory often suggest that observing other aquatic animals tells us that the development of hind legs for aquatic propulsion is extremely unlikely.

Safe to say, whichever theory you subscribe to as to why frogs move as they do, it is clear that there is no frog tail because it would interfere with the way they move.

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