Strimmers, bonfires and netting are among garden hazards that can harm hedgehogs, so take precautions during Hedgehog Awareness Week and beyond.

Hedgehogs are welcome visitors to our gardens, eating slugs and other pests, and helping achieve the balance of nature.

However, campaigners have said numbers have fallen by as much as 50% since 2000 in the UK countryside, and it is believed there are now fewer than a million hedgehogs in Britain.

Hugh Warwick, of the British Hedgehog Preservation Society (britishhedgehogs.org.uk), says: "Gardeners need to get rid of the cult of tidiness, the idea of having the garden manicured and maintained to the nth degree. We need to let the life within the garden live a little bit more. The biggest hazards are in the way we manage the garden. And careless gardening is the chief hazard."

The BHPS offers the following advice on how to take care not to harm these prickly mammals during Hedgehog Awareness Week, and beyond...

1. Watch your strimmers

This may be the ideal time to tidy up any rough patches of grasses, but they may conceal a hedgehog asleep in their day nest on a warm summer's day.

"A hedgehog doesn't have a 'fight or flight' response like other animals, who will beat a hasty retreat when confronted by the noise of an oncoming mower or strimmer," Warwick warns. "A hedgehog will roll into a ball, which copes with everything except eagle owls, badgers, cars and strimmers."

2. Put back grates

If you remove grates to clear your drains of leaves and other debris, make sure you replace them, otherwise hedgehogs could fall in and become trapped.

3. Keep netting propped up

Keep pea netting 22-30cm (9-12in) off the ground so hedgehogs can pass under and plants will grow to the netting.

"The problem is that the hedgehog's reaction to threat is to frown and then roll into a ball. When a hedgehog gets caught in netting, it can't reverse out because their spines are lying flat backwards. Then they roll into a ball which further entangles them," Warwick explains.

4. Take care turning compost heaps

If you have a traditional compost heap of vegetation cuttings and leaves at the back of your garden - one that isn't in a container or on a raised palette - make sure you're careful when turning it, as it may house nesting hedgehogs that are enjoying the warmth.

5. Create an exit from ponds

Hedgehogs enjoy water and are good swimmers, but they do need an exit from a wildlife pond or pool, so either create a gently sloping edge or place half submerged rocks in the water so they can easily get out.

"Water is crucial for hedgehogs. Shallow dishes on the ground are also great for hedgehogs and insects. If your pond is ornamental with vertical sides, if you can't build a beachy bit, put in a ramp," Warwick suggests.

6. Don't leave litter

Dispose of litter responsibly. Every year hedgehogs are injured by litter.

"The most regular hazard hedgehogs face is elastic bands. Hedgehogs will push through the undergrowth and if an elastic band is on its side, they will push through that. Once it goes over the spines, they can't disentangle themselves."

7. Avoid pellets and pesticides

Avoid using pesticides and slug pellets in your garden. Not only can these harm hedgehogs, they can also damage their food chain. Use organic methods instead.

8. Feed correctly

Hedgehogs are lactose-intolerant, but they don't know they are, warns Warwick. So don't feed them milk or bread as they will end up with stomach upsets.

They are carnivores, and their favourite diet is worms. When the weather is cold and dry, leave out foods like meaty pet food (not containing fish) within an upturned box with a side entrance that you can turn into a feeding station.

"If you put a barrier inside the box, creating a tunnel as you go in, and put the food near the front wall of the box, the hedgehog can snaffle in but cats can't. By creating a dead end, rats will be less willing to linger," Warwick notes.

9. Beware of bonfires

If you must have a bonfire, check carefully underneath the pile before you light it. Hedgehogs may be nesting beneath the debris. Lift the base with poles or broom handles (not a fork) to check for hedgehogs, and rescue them before lighting.

What do you do if you find an injured hedgehog?

"If you see hedgehogs purposefully out in your garden during the daytime, there's generally something wrong as they are nocturnal," says Warwick. "If it looks like it is sunbathing or drunk, those are the key concerns, both indications that the hedgehog has hypothermia and will probably die if you don't intervene."

Use gardening gloves to pick it up, bring it indoors and put it in a high-sided cardboard box with an old towel or fleece in the bottom for the hedgehog to hide under, the BHPS advises.

Fill a hot water bottle so when it is wrapped in a towel there is a gentle heat coming through and put that in the bottom of the box with the hedgehog, ensuring it has room to get off the bottle should it get too warm. Don't let the bottle go cold, so change the water frequently. Once you have the hedgehog settled, call the British Hedgehog Preservation Society (BHPS) on 01584 890 801.

Hedgehog Awareness Week runs May 3-9. For more information visit britishhedgehogs.org.uk.