As distant relatives of shrews, hedgehogs have changed little in the past 15 million years. 
Hedgehogs are one of only three animals to hibernate in the United Kingdom and Britain’s only spiney mammal. They have between 5000 - 7000 spines on their back which raise and lower if they feel threatened. Hedgehogs will curl up in a ball when they feel threatened and use these spines to protect themselves.
Baby hedgehogs are called 'hoglets' and a group of hedgehogs is called an 'array'.
Hedgehogs are lactose intolerant, rather than milk they prefer that you to leave out cat or dog food and water for them.
Hedgehogs have very bad eyesight but their senses of smell and hearing are impeccable, they are nocturnal creatures meaning they only come out at night.
In one night hedgehogs can walk over two miles.
Hedgehogs are insectivores, meaning they love the bugs in your garden, they enjoy foraging around in bushes and the undergrowth, that's how they got their name.
Hedgehogs are known as a 'gardener's friend' as they eat all the insects that nibble on our much loved plants.
Hedgehogs haven't always been called hedgehogs, a long time ago they were called 'urchins'.
In decline throughout much of UK, many are killed on roads. Strimmers, tidy gardens, bonfires and insecticides/molluscicides are widely considered detrimental to their population also a high level of predation by badgers in some areas. Persecuted locally where implicated in bird declines. Protected by law in much of Europe.
Fragmentation is a major issue affecting hedgehogs. This means that fences, walls, new developments and roads are all breaking up green spaces that hedgehogs depend upon.
These barriers are making it harder for hogs to get from one green space to another.