Sir - Regarding the ongoing correspondence concerning fortnightly refuse collection; I have seen little evidence of plastic bags being torn open by rats.

Before the introduction of the large wheelie bins, one frequently saw bags being torn open by magpies and crows.

The reason for the increase in the rat population may be due to unsuitable composting containers.

For many years my wife and I have composted most of our kitchen waste. Initially the enclosure was made of wood. But when we began getting visits by rats, and on one occasion found that they had built a nest deep in the compost, we decided to invest in a large plastic composting container. Even this had to be placed on a concrete base to stop the rats gaining access.

While not wishing to discourage people composting as much of their waste as possible, they should make sure that it is fully ratproof.

If people don't have space for composting, then I can't believe it is impossible to find a ratproof container for the plastic bags.

V. Berry, Oxford