The Common Frog

This blogpost is about our common UK frog. An amphibian spending most of the time in water. They over-winter underground, in compost heaps or at the bottom of ponds but they don't actually hibernate. They emerge on warm days to forage and, in Spring, to mate. We all learned the lifecycle in school, but (to me) it’s more interesting as an adult.

For several years we’ve found frogspawn on the allotment site. It's most noticeable when spawned into puddles on empty plots, so its gathered up and divided between the various small ponds. Apparently frogs spawn into puddles more often than toads do but it's a risky business with likely predation or, more often, the puddle drying out.

After just 4 days the eggs have changed from a black dot to a small comma shape. Given the timing, frog eggs can freeze and any spawn with a white egg is unfortunately dead. It's the start of a hazardous life - only 5% of spawn is likely to reach maturity; full maturity is reached at 4 years old.

A week after the first changes, look very closely and they appear like this, with external gills. At this early stage of development they form a writhing mass of tadpoles eating the remains of their gelatinous spawn.

Within a further 4 days a fold of skin forms over the feathery gills so they become internal gills. At about 1cm long they now look like 'normal' tadpoles swimming about searching for food.

At this stage they are vegetarian, mostly eating algae.

As they grow larger, they become carnivores and will eat what they find in the water - as well as each other if there’s not much else available 😖
Their metamorphosis begins with their back legs forming - they're on their way!

This ones head and body have become much more froggy, even with the classic frog patternation, though it has a lot further to go with that long tail and no front legs yet..

Now with front legs, a shrinking tail and formed lungs they are able to start emerging from the water so need an exit route available to them.

As you can see they can develop at different rates. This one is lacking the full froggy fetaures but clearly it has formed lungs.

And, here at about 16 weeks old - the tiniest perfect froglets you’ll ever see - smaller than the tadpoles they developed from. Some tadpoles don’t go through the metamorphosis in their first year and I’m not sure many survive remaining as tadpoles. They would even make a tasty treat for an adult frog 😕

At this stage they disappear off into the undergrowth to grow into lovely little frogs which are spotted occasionally. I remember going to a show at nearby West Woodhay and a field was crawling with tiny froglets and toadlets making their journey from the lake to surrounding areas. It was amazing to see such huge numbers!

They usually move away from their pond until they're mature enough to mate (about 3 years) when they return to their spawning ground.

They are welcome on the allotment as they enjoy slugs along with insects and earthworms.

We do love to see a frog or, even better, two!

These photos were taken on the site across different years. Frogspawn normally arrives in late March, sadly in rather short supply on site this year. We’ve seen various colours of frog from dark brown to green-ish through orange to golden but they all have the same markings behind their eyes and the stripes down their back ridges.