Seventeen species of hedgehog exist worldwide. Hedgehogs are native in Europe, the Middle East, Africa, and central Asia. They were introduced to New Zealand by England and quickly became an invasive species. Hedgehogs are omnivorous and threaten insect, snail, lizard, and bird populations due to a lack of natural predators in New Zealand. Hedgehogs may tighten the orbicularis muscle (a circular muscle structure similar to a sphincter) on their back to hide their head, legs, and belly in a coat of prickly erect spines. Hedgehogs are primarily nocturnal, though some may be crepuscular. Hedgehogs typically take refuge in the empty burrow of another small animal, or a burrow they dug themselves. However, hedgehogs can occasionally take refuge under rocks or in thick vegetation, or anywhere dark and secluded. Hedgehogs tend to be solitary, though not to the extent of hamsters. Some captive bred females crave the companionship of another hedgehog and occasionally show bonding tendencies when housed with another female; male hedgehogs should not be housed together as they will fight once they reach sexual maturity.
