Anatomy

A ball of hair with ambitions

Spines, muscles, legs and senses. The European hedgehog, Erinaceus europaeus, from the outside in.

A juvenile European hedgehog walking on tarmac in Sweden, its legs visible under its spines — Legs! Hedgehogs have more of them than you think — well, more leg per leg.Photo: Calle Eklund/V-wolf · CC BY-SA 3.0 · Commons

The spines

A European hedgehog carries roughly 5,000–7,000 spines, each about 2–3 cm long. Hedgehog Street

Spines are hollow hairs stiffened with keratin, the same protein as your fingernails. They are not poisonous or barbed and, unlike porcupine quills, do not easily detach. Wikipedia

Young hedgehogs shed their baby spines for adult ones, a process called quilling. source

Not a porcupine

Spines are a defence, not a weapon. A hedgehog doesn’t shoot them, and they don’t come out in your hand. That’s porcupines, and porcupines are rodents. source

Rolling up

Two large muscles in the back control the position of the quills, and a draw-string muscle lets the hedgehog curl into a ball. source A ring of muscle works like a draw-string to pull the spiny skin around the body. Hedgehog Street

A European hedgehog almost completely rolled into a ball on grass — Almost fully rolled. The face, feet and belly are all tucked inside.Photo: von Thomas Steiner am 25.6.2005 in unserem Garten in Weinzierl fotografiert · CC BY-SA 3.0 · Commons

Size and weight

European hedgehogs measure about 160 mm (head and body) at weaning, rising to 260 mm or more in large adults. The tail is just 20–30 mm. source

Adults usually weigh over 1,100 g; the record is 2,000 g, though few wild ones top 1,600 g even in autumn. source

Legs, feet and senses

Under the skirt of spines are surprisingly long legs (about 10 cm) and five clawed toes on each foot. Hedgehog Street Eyesight is poor; hedgehogs find food mainly by smell and hearing. Hedgehog Street

The underside of a European hedgehog’s front foot, showing five clawed toes — A front foot: five toes, strong claws for digging.Photo: T137 · CC BY-SA 3.0 · Commons

Skull of a European hedgehog from the side, showing many small sharp teeth — A skull from Museum Wiesbaden: an insect-eater’s teeth.Photo: Klaus Rassinger und Gerhard Cammerer, Museum Wiesbaden · CC BY-SA 3.0 · Commons

Colour

Most hedgehogs are brown with pale tips to the spines. Pale "blonde" (leucistic) hedgehogs are rare, except on Alderney and North Ronaldsay; on Alderney about a quarter of the population is thought to be blonde. source

Venom

Hedgehogs have some resistance to snake venom thanks to a protein called erinacin, but not much: a viper bite can still kill one. source Hedgehog Street's myth-buster: hedgehogs are not immune to snake bites. They have only partial resistance to venom, and a bite to the face or leg could still kill one, but Britain's only venomous snake, the adder, can't bite through the spines. Hedgehog Street

A very old design

Hedgehogs have changed little over the last 15 million years. source The word "hedgehog" came into use around 1450, from Middle English heyghoge: hedge (where it lives) plus hog (for the piglike snout). source