Hedgehogs have been around since the dinosaur age, but numbers have declined by 25 per cent in just the last decade.
According to some researchers, there are only around a million hedgehogs left in the UK - and they may be completely gone by 2025.
Beryl Steadman has been rescuing hedgehogs at the Pembrokeshire 'Hog-spital' in Haverfordwest for 13 years.
She says the cold weather and Bonfire Night mean a particularly tough time for them, but there are things people can do to help them survive.
Beryl has issued the following advice to help people protect hedgehogs:
Bonfires: Set on day of lighting. Shine a torch underneath or light one side first so hedgehogs can find a way out.
Ponds: Hedgehogs can swim but they die when they can't get out of water. They need a slope or something to grip.
Feeding stations: Encourage hedgehogs into your garden by creating a feeding station out of a bed storage drawer. Cut a hole in one end and put food at the other and put in a safe place so they can visit. They like meat-based dog food the best.
Size: Small hedgehogs won't survive the winter. If you find one that is under 650 grams, take it to a rescue centre.
Strimming: Hedgehogs often hide in long grass. Check carefully before mowing or strimming.
Gardens: Hedgehogs like to roam and can travel a couple of miles a night to forage for food. One garden is not enough space, so they need access points between fences.
Chemicals: Try not to use slug pellets or pesticides in your garden as not only will they reduce the number of insects available for hedgehogs to eat. They might also make hedgehogs very ill, or even kill them.
Hibernation: Sleeping hedgehogs are warm to touch; hibernating ones are colder. Do not disturb hibernating hedgehogs as it may cause them to stir and use up valuable energy reserves.
Hedgehogs are now on the endangered species list.
It's illegal to keep them as a pet but there are rescue centres across the UK that can help.
Alexandra Hartley has been finding out about one in Haverfordwest: