It is late February, the cold weather has moved away and the frogs have moved back in. It’s been a couple of years since they were last here, but here are their newly-laid eggs and the female is hiding beneath the leaf in the top left corner of the photograph. What is a frog and how is it having adventures in Nowhere Wood?
Frogs are amphibians, animals with backbones that live for most of the year on land, but which have to return to water to breed. A female with eggs is popular with males, which compete with each other to get close to her.
When she releases here eggs into the water, the males release their sperm onto the eggs. Fertilisation takes place in the water. The female lays about 2 000 eggs and many of them die. The brown eggs in the top photograph are probably a clutch of eggs that have died.
Inside the egg, the embryo is growing into a juvenile tadpole, feeding on the jelly that surrounds it. It will grow a tail and gills and become a free swimming tadpole. Soon, the tadpole will break free and have to make its way as an independent animal, all of the while developing into the adult frog.
There are dangers in the water: tadpoles become carnivores and will eat each other and there are other predators, too. There is also a real chance that the water in the pond will disappear if we have a prolonged dry spell.
The frogs in Nowhere Wood are having adventures, moving forward into an unknown future, with no certainty of success. Most of these eggs will be eaten and will become food for other organisms; one or two might survive. Most years, frogs return to the water to breed, as frogs everywhere have done for the last 265 million years.
1. The survival of the frogs is not just due to chance. There is competition between male frogs to get close to the females eggs. How does this help to increase the success of the mating?
2. There is also competition between tadpoles for food. How does this help ensure that some frogs will survive to become adults that can reproduce for themselves?
3. What, do you think, is a frog?
Frog news update:
One week on, and the spawn has floated to the edge of the pond and the adds are swollen because they have taken up water. They still look healthy. Fingers crossed for the next stage!