Hedgehogs are solitary, nocturnal mammals in the family Erinaceidae, order Eulipotyphla, which includes shrews and moles. The African pygmy hedgehog (Atelerix albiventris), also known as the white-bellied, four-toed, or central African hedgehog, is native to dry, open habitats in central and eastern Africa. Hedgehogs are nocturnal and very active, traveling for miles in search of prey. In the US, some states and municipalities require a permit to keep a hedgehog as a pet; in some parts of the US it is illegal. Additionally, a USDA permit is required to breed, transport, sell, or exhibit hedgehogs.
Anatomy, Physiology, and Behavior of Hedgehogs
The dorsum of a hedgehog, also known as the "mantle," is covered in a dense coat of keratin spines; each spine is firmly attached within the follicle by a basal bulb. A narrowed portion at the skin surface allows for spines to be held flat against the body or erect in a defensive position. It is difficult to pull a healthy spine from the follicle without breakage. The mantle has a thin, mostly hairless epidermis and a thick, fibrous dermis with abundant adipose tissue and minimal vascularization.
A wary hedgehog will erect the spines and crouch. When a hedgehog is frightened, the panniculus muscle will contract and pull the loose spiny skin around the entire body. The panniculus is thickened at the rim to form the orbicularis, a purse-string–like muscle that cinches the mantle closed around the animal, forming an intimidating ball of raised spines. For selected physiologic data for African pygmy hedgehogs, see Physiologic Data for African Pygmy Hedgehogs Physiologic Data for African Pygmy Hedgehogs .
Hedgehogs have brachydont teeth. The first incisor in each quadrant is large and projects forward, and there is a gap between the maxillary first incisors in which the mandibular incisors sit when the jaw is closed. The molars are relatively flattened with multiple cusps. Hedgehogs have a simple stomach and a vomiting reflex.
The male has a conspicuous prepuce that opens mid-abdomen. There is no scrotal sac; the testes are located in a para-anal recess surrounded by fat and can be palpated in reproductively active males.
The female urogenital opening is a few millimeters cranial to the anus. The uterus is bicornuate, with dramatically curled horns, a single cervix, and no uterine body. Hedgehogs are polyestrous and breed throughout the year in captivity. Ovulation is believed to be induced, and sterile matings with pseudopregnancy may occur. Hedgehogs are born with closed eyes and ears and without hair; at birth, the spines are covered by a membrane that dries up and disappears within the first few hours of life.
Hedgehogs easily dig, climb, swim, and run. Although they have sensitive olfaction and hearing, their eyesight is poor. While foraging, hedgehogs make a variety of snuffling noises; when agitated, they make a loud hissing sound interrupted by cough-like and puffing sounds. Hedgehogs in intense distress may scream. With patience, most hedgehogs learn to accept handling. Hedgehogs are unique, inquisitive pets and generally do not bite.
Hedgehogs engage in a unique behavior called self-anointing, or anting. This behavior may be elicited by a variety of substances, particularly those with a strong odor. The hedgehog licks, bites, or holds the material in its mouth, mixes it with frothy saliva, and applies the saliva mixture to its spines with its long tongue. The purpose of this behavior is unknown.