Wednesday, 28 June 2006

Unexpected visitor raises a question or two

It came as something of a shock the other morning to discover a toad sat in the middle of the kitchen floor sporting a look of passive acquiescence. I was still bleary-eyed, roused from sleep by two dogs intent on their morning walk, and there it was, sat on the carpet, raising the question of how it had made its Houdini-like appearance in my kitchen. Needless to say the dogs were decidedly non-plussed, having developed a grudging respect for toads at a young age. Anything that can inflate itself and exude an unpleasant chemical when approached by an overly-inquisitive puppy soon earns respect. I picked up the toad and deposited it in the garden. The toad was a youngster, not a toadlet but a two-inch long juvenile from last year. I suspect that it had clambered up the pipe that links the outlet from the washing machine to the outside drain but while this answered the question of how it had got into the kitchen it did raise the question of where it had come from.

Like our other amphibian species, the common toad is dependent upon water for breeding but at other times of the year it can be found in gardens, woodland and even grassland. Research into the ecology of the common toad has revealed that individuals typically overwinter within a 1,000 metres or so of their breeding pond. Since our small wildlife pond only ever has frogspawn, it seems likely that there is a suitable breeding pond nearby, and that this individual came from there. Toads favour larger-sized ponds than frogs, with an optimal size being about 1,000 square metres, with plenty of marginal cover. They also seem to prefer ponds containing fish, perhaps because fish find their tadpoles unpalatable but will feed on the newt and frog tadpoles with which the toads compete. Deliberate attempts to introduce common toads into garden ponds invariably fail so competition with other amphibians may not be the only reason why we see adult toads in our gardens but not breeding in our ponds.

There is an interesting footnote to this episode. Last year, our new neighbours were figuring how to convert a rather large and overly deep pond into something more wildlife friendly. The previous owner had dug the pond in the expectation of populating it with carp but never did. He only managed to fill it with water just prior selling the house. Before the pond could be adapted several strings of toad spawn appeared followed by a number of tadpoles. With no vegetation within the pond these soon perished and that was that. Perhaps a new and bigger wildlife pond might tempt them to breed again.

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