By Charlotte Owen
It’s frogspawn season - one of the most exciting events in nature’s calendar. We look forward to it every year, eagerly awaiting the return of the frogs to water. Will they make it safely back to the garden pond after their winter sleep, and when will they arrive? Will they spawn this year? When will it appear, and how much will there be?
The timing of this great event can vary a lot from year to year, so we never know for certain, and the weather is a significant factor. If we have a mild winter, the frogs will be out early and might even spawn in January – but if it’s cold and icy they won’t come out until it thaws. Frogs spend the winter in hiding under logs, in compost heaps and other sheltered spots, and they will only emerge when night time temperatures are consistently mild enough. As soon as they detect that conditions are right, they will leave their overwintering sites and head straight back to the water – often returning to the pond where they were born. Spawning usually peaks from late February into March and conditions have been good this year, so most frog ponds should have spawn by now and some will have hatched already.
Frogspawn looks like a clump of translucent jelly beads, each with a black dot at the centre. Those black dots will eventually become black squiggles as the tadpoles inside start to grow, feeding on their jelly egg cases until they’re big enough to swim free. It can take anywhere from a week to a month for freshly-laid spawn to hatch into tadpoles. They tend to develop faster in a warm, sunny spot, so shallow ponds are perfect for frogs.
When they hatch, these tiniest of tadpoles are still quite fragile and they tend to stick themselves to a piece of pondweed (or the edge of a tank if you’re rearing them) for the first week or so while they finish digesting their jelly. Once that’s gone, they need to seek out more food so they start swimming around in search of pond plants and algae. They have little feathery gills so they can breathe underwater and will develop tiny teeth for grinding up food. They’re basically little eating machines, so they have a very long, coiled gut to digest all that plant matter. As they grow, they change shape from little black lines to proper little tadpoles as their heads get bigger and rounder, and the tadpoles get stronger and more robust. They develop golden brown speckles as they grow, and will eventually sprout legs – the back legs come first, followed by the front legs. Then they gradually re-absorb their tails, since they won’t be needing them any more, and they use these nutrients to complete their transformation into tiny froglets. The whole process takes several months and the resulting froglets will be ready to leave the pond in the summer.
We always get lots of frogspawn questions every year and we know you’re keen to take good care of your garden frogs. This year, we’re celebrating tadpole season with a special Froggy Friday event online, where you can ask all your froggy questions and learn more about these fascinating creatures and their miraculous metamorphosis. If you’re lucky enough to have a garden pond full of tadpoles, you’ve got a great opportunity to watch them develop over the next few weeks – but if you haven’t, we’ll also be sharing regular tadpole video diaries as we follow the progress of this year’s tadpoles in our own garden pond.
To join in with Froggy Friday, visit our Facebook page (www.facebook.com/SussexWildlifeTrust) from 10:30 on Friday morning (27 March) or tweet us a question using the hashtag #FroggyFriday. We’ll also share lots of Froggy Friday facts and tips on looking after your garden frogs on our website, and of course you can always contact me via WildCall (email@example.com) - we’re still up and running and would love to hear from you.