Spring is a wonderful time of year here at Rutland Water Nature Reserve. We get to witness nature’s springtime joys; lambs in the fields, blue tit chicks fledging just outside the Centre and our osprey chicks bringing great excitement. But what about other wildlife joys I can bring to your attention? Tadpoles!
Many of us love seeing these jelly like blobs swimming at the surface of a pond or in a tank. Our educational tank at the Centre has been home to our tadpoles. Keeping their food topped up and moving them out of the tank, our excitement of releasing the froglets into the wild has been a proud moment! We are giving them the best start in life, like proud parents! Or so we thought……
To our surprise a visitor posted an amazing shot of a grass snake surfing along the top of our pond, posting it on our Facebook page. This stunning photo was brilliant to see and then the penny dropped! It’s at the pond where the froglets were being released. What a discovery!
This news at first was one of shock but at the same time teaches us not to get too attached to jelly blobs! Froglets have many predators, one of these being grass snakes. What is more interesting is that in this discovery, it opened up a bigger picture of understanding about the life cycle of a froglet.
When tadpoles change into froglets it is known as a process called metamorphosis. It is an amazing transformation that rapidly takes place in such a short time. The tadpole changes from having cartilage around its skull to bone, it has to develop vertebrae and loose its tail, plus develop lungs to breathe on land!
So, its back legs will develop first. At around four weeks they produce teeth and around six weeks their mouth starts to widen. Around this time skin will develop around the gills. At approximately ten weeks old, their eyes and eye-lids develop. The tadpole’s tail will become shorter and absorb into the body. Particular features like their teeth, tongue and bones start to take shape. The internal organs will grow. The intestines must develop so that a tadpole eating algae and plants can transform to eating meat.
Last to transform are its lungs and front legs. The gill slits are absorbed back into the body so they can no longer breathe under water. The froglet then takes to the verges of a pond or floating objects in a tank. Believe it or not froglets can drown because they are weak swimmers. So survival starts here to become opportunist predators building up their strength using newly constructed leg muscles. It usually takes approximately a further six weeks for the froglet to fully emerge as an adult frog.
This is an extremely complex chain of reactions that has to happen in the correct order for the tadpole to continue to function in water until it is ready to hop onto land. Around 1% to 5% of the eggs laid will actually make it to adulthood so competition is fierce.
Tadpoles and froglets have been known to begin eating each other as they turn carnivorous. Leading us nicely onto other carnivorous predators! The grass snake on this occasion has been very lucky!