Since the current pond was constructed in autumn 2002, frogs have spawned each spring. The photos on this page show the frogspawn and developing tadpoles. For later stages in the development, see the pages on froglets and frogs.
This year, for the first time, I've given most of the frogspawn away, to my mum, who also has a pond in her garden. I think that three or four lots of frogspawn per year is probably a little too much for this small garden to sustain. My mum's garden is bigger, and near a beck that runs along the bottom of the garden, so I'm hoping it will be a happy habitat for them. She's keeping me updated, so I'll report on their progress.
Frogspawn first appeared in the pond in the spring of 2003 - the first spring after the pond was constructed. On the morning of 1 April the spawn was floating in the middle of the pond, attached to a marginal plant whose top leaves were just breaking the surface of the water. Frogspawn might not be the most beautiful thing to look at, but it seemed to me a beautifully hopeful and jolly sight that rather cloudy, damp April morning.
It was a slow process, the development, but amazing nonetheless. The mere black dots turned into things that moved and grew tails, still gathered on the jelly-like substance that had encased them. By early May 2003 they were free and swimming, the pond full of the wiggling dark shapes of tadpoles.
The arrival of frogspawn in the garden pond seems to have happened at an earlier date each year. This doesn't seem to necessarily correspond with the development of tadpoles into froglets. In 2005 the frogs were seen mating by mid-March and the first spawn was seen in the pond on 18 March. For the first time, several lots of frogspawn were deposited together in the centre of the pond. But by July, the tadpoles were still in the pond and there was no sign of froglets, which the previous year were emerging by 22 June, so development seemed to be taking longer.
The tadpoles feed on the algae in the pond, and as the water warms up the algae grows, providing them with plenty to eat. When the sun is shining on the shallow sides of the pond, they seemed to congregate there, as the photos (right) show.
The tadpoles' tails begin disappearing and their bodies begin to change shape. Tiny legs begin to form, odd spindly things that look like they will never be strong enough to take the tadpoles onto land. As the tadpoles swim through the water of the pond their newly-formed legs carry on growing, while their tails continue to shrink.
The BBC website provides some useful information on tadpole development:
"When tadpoles hatch they have gills that allow them to breathe underwater. After 9 weeks they have lost their gills and developed lungs, and therefore must swim to the surface to breathe. As they grow, tadpoles begin to feed on insects as well as plants. Hind legs develop between 6 and 9 weeks, and front legs are fully developed after about 11 weeks. The tail begins to be absorbed by the developing tadpole, and by 12 weeks it has practically disappeared, leaving a tiny froglet. At this stage the tadpoles are less dependent on water and will hide in long grass in and around the pond."
- from www0.bbc.co.uk/nature/wildfacts/factfiles/483.shtml
While the pond seemed to contain some tadpoles that were less advanced, and still had tails, and barely visible legs, by the third week in June 2004 some of the tadpoles were developed enough to begin their move out of the pond and on to land. I was lucky enough to be around in the garden at the time, and able to take photos, shown on this page and the froglets page.