Although the adage that you’re never more than six feet away from a rat is something of an exaggeration, it’s true that they will probably be nearby, particularly in urban areas. They often exist hand in hand with humans, making use of whatever food is available, including spilled bird seed and any fruit and veg you may be growing.

WHY THEY’RE NOT WELCOME
Rats can carry diseases including salmonella and Weil’s disease. However they often don't do any actual damage, although if they are digging tunnels in the garden this can be a problem.

HOW TO DETER THEM
There isn’t really anything you can do to stop rats entirely, but you can make your garden less attractive by reducing food sources. Don’t leave out food for other wildlife overnight, tidy up any fallen fruit and stop up any holes in the shed that could let rats enter. Use a compost bin with a solid bottom and a lid, or fit rat-proof wire mesh at the base of the bin. Or try to raise your bin off the ground and don’t put cooked food in the compost. Rats dislike disturbance and newness, so tidy up any areas where they could be hiding. If rats are a recurring and serious problem, then traps or poison can be used, but bear in mind
the risk of secondary poisoning, which can occur if the poisoned rats are eaten by another animal, such as an owl or red kite. You must also take great care that the poison can’t be found by other wildlife, domestic pets and children.
It may be best to contact a local pest controller for help and advice. You can also buy ultrasonic rodent repellents that plug in to an electric socket. One member tried this method in a garage with some success, but pest-control experts at Rentokil say that although these gadgets may have a limited effect for
a few days, they are unlikely to affect an established colony.