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Overview of Hedgehogs

By James W. Carpenter, MS, DVM, DACZM, Zoological Medicine, Department of Clinical Sciences, College of Veterinary Medicine, Kansas State University ; Dana Lindemann, DVM, Department of Clinical Sciences, Kansas State University

Hedgehogs are in the family Erinaceidae, within the order Insectivora. The central African hedgehog (Atelerix albiventris), also known as the white-bellied, four-toed, or African pygmy hedgehog, is native to dry, open habitats in central and eastern Africa. They are nocturnal and very active, jogging for miles in search of invertebrate prey. In the USA, it is illegal to own a hedgehog as a pet in some states and municipalities; in other states, a permit is required. Additionally, a USDA permit is required to breed, transport, sell, or exhibit hedgehogs.

Anatomy, Physiology, and Behavior:

The dorsum is covered in a dense coat of keratin spines; each spine has a basal bulb that firmly attaches it within the follicle, with a narrowed portion at the skin surface. Healthy spines are difficult to pull from the follicle without breakage. The spined skin has a thin and hairless epidermis and a thick, fibrous dermis with much fat and few blood vessels. A wary hedgehog will raise the spines and crouch. If a hedgehog is frightened, contraction of the panniculus muscle pulls the loose spiny skin over the entire body. The panniculus is thickened at the rim to form the orbicularis, a purse-string–like muscle that closes the spined skin over the animal. For selected physiologic data for African pygmy hedgehogs, see 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. The stomach is simple, and a vomiting reflex is present. 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 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 hairless, with closed eyes and ears; at birth the spines are covered by a membrane that is removed within the first few hours of life.

Hedgehogs are adept at climbing, digging, swimming, and jogging. While they have sensitive olfaction and hearing, their sense of vision is not as well developed. Foraging hedgehogs normally emit a variety of snuffling sounds; agitated hedgehogs make a loud hissing sound that may be punctuated with various puffing and cough-like sounds. With intense distress, a scream may be emitted. With patience, most hedgehogs learn to accept handling.

Hedgehogs demonstrate 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 takes the material into the mouth, mixes it with frothy saliva, and applies the mixture to its spines with the tongue. The purpose of this behavior is unknown.

Physiologic Data for African Pygmy Hedgehogs

Average body weight

Male: 400–600 g; Female: 300–400g

Life span

Average 4–6 yr, may live to 8 yr

Body temperature

95.7°–98.6°F (35.4°–37.0°C)

Adult dental formula

2 (I 3/2:C 1/1:P 3/2:M 3/3) = 36 (variations have been noted)

GI transit time

12–16 hr

Heart rate

180–280 bpm

Respiratory rate

25–50 bpm

Age at sexual maturity

2–3 mo

Reproductive life span

Male: throughout life

Female: 2–3 yr

Gestation

34–37 days

Litter size

3–4 (range 1–9)

Birth weight

10–18 g

Eyes open

14–18 days

Deciduous teeth eruption

Begins on day 18; all deciduous teeth erupted by 9 wk

Permanent teeth eruption

Begins at 7–9 wk

Age at weaning

5–6 wk (start eating solids at 3 wk)

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