Perhaps the first thing to do is to contact your local environmental health pest control officer. Some councils are willing to treat garden infestations; others will only attend if the infestation has spread indoors. However they should be able to give you good advice but will almost certainly say the only effective treatment is a combination of poison and traps. If you decide to consult a private pest control operator ensure that he is a member of a professional body such as the British Pest Control Association (BPCA).
If you don’t want to use poison you are quite restricted in what you can do. There are humane rat traps available but then you have the problem of disposing of the live rats. Because they are a pest and potential carriers of disease, you are not allowed to release them anywhere else.
However there are several things you can do to try to make your garden less pleasant for rats.
- Rats mainly live in sewers. Check your drainage covers and inspection chambers, and, if necessary, have the pipes checked for cracks or breaks.
- Don’t let your garden get overgrown and keep it free of rubbish that could provide nesting places.
- Check under decking and in sheds for nests.
- Rat proof your shed. Rats can get in through very small gaps so fill them all in.
- Don’t leave food out for other wildlife and put bird food on a bird table or use a hanging net.
- Check that your rubbish bins have well-fitting lids.
- Use a properly-designed composter and don’t put any meat or non-vegetable matter in it. Avoid putting cooked food in it too.
- At some stores you can buy an ultra sonic pest repeller. These detect movement and emit a sound outside the normal human hearing range and are said to be very effective in deterring night-time visitors. They don’t affect humans, birds or fish.
- Get a very large cat!
We understand your reluctance to use poison but if the infestation is as severe as you suggest, and especially in view of the fact that you have children who play in the garden, a carefully-controlled routine of poison and trapping might be the best solution.