Hedgehogs are easily recognized by their
spines, which are hollow hairs made stiff with
keratin. Their spines are not
poisonous or
barbed and, unlike the quills of a
porcupine, do not easily detach from their bodies. However, the immature animal's spines normally fall out as they are replaced with adult spines. This is called "quilling". Spines can also shed when the animal is diseased or under extreme stress. Hedgehogs are usually brown, with pale tips to the spines, though leucistic 'blonde' hedgehogs are found on the Channel Island of
Alderney. microscopy) Hedgehogs roll into a tight spiny ball when threatened, tucking in the furry face, feet, and belly. When the animal encounters a new scent, it will lick and bite the source, then form a scented froth in its mouth and paste it on its
spines with its
tongue. Some experts believe this might serve to
camouflage the hedgehog with the local scent, and might also lead to infection of predators poked by the spines. Anointing is sometimes also called
anting after a similar behavior in birds. Like
opossums, mice, and
moles, hedgehogs have some natural
immunity against some
snake venom through the protein
erinacin in their muscles, though in such small amounts that a
viper bite may still be fatal. In addition, hedgehogs are one of four known mammalian groups with natural protection against another snake venom,
α-neurotoxin. Developing independently,
pigs,
honey badgers,
mongooses, and hedgehogs all have mutations in the
nicotinic acetylcholine receptor that prevent the binding of the
snake venom α-
neurotoxin. The
sense of smell has been little studied in the hedgehog, as the olfactory part of the mammal brain is obscured inside the
neopallium. Tests have suggested that hedgehogs share the same olfactory electrical activity as cats. ==Diet==