I have just read Leslie Frizell's letter asking for some tadpoles (April 20).

This year, I had many frogs mating from February 12, two weeks earlier than last year, leaving a great many clumps of spawn.

However, it has all disintegrated so I also have no tadpoles. What is more worrying is I am not even sure I have any older resident frogs any more.

These are vital in keeping the slug population down. So what has happened? Have the parent frogs eaten poisoned food and is the spawn infertile as a result?

I understand one should not introduce spawn or tadpoles from another pond because of passing on disease. Can anyone explain why?

-M Davies, Wayfield Avenue, Hove