A hedgehog's spines are actually modified hairs made of a tough material called keratin - the same stuff your fingernails are made from. Each spine is hollow, which makes it both light and strong. When a hedgehog rolls up, even a fox finds it very difficult to unfurl.
Hedgehogs are insectivores, meaning they eat insects and other invertebrates. On a single night, a hedgehog might travel two kilometres snuffling through the undergrowth for beetles, earthworms, caterpillars, and slugs. Their long pointed snout is perfectly designed for rooting through leaf litter.
In Belgium, hedgehogs hibernate in winter. From around November, they find a quiet spot under a pile of leaves or inside a log pile, curl up, and their body temperature drops to near-freezing. Their heart rate slows from about 190 beats per minute to just 20, saving enormous amounts of energy.
In spring, hedgehogs wake up very hungry. This is when Belgian garden owners might leave out a bowl of meaty cat food or dog food to help them recover - water is even more important, as hedgehogs get very thirsty after months of hibernation. Milk, however, upsets their stomachs, so it should be avoided.