Hedgehog

This article is about the spiny mammal. For other uses, see Hedgehog (disambiguation).

A hedgehog is a spiny mammal in the subfamily Erinaceinae, part of the eulipotyphlan family Erinaceidae. There are 17 kinds of hedgehog, grouped into five genera. They live in parts of Europe, Asia, and Africa. They also live in New Zealand, where they were introduced. Hedgehogs are not native to Australia, and no living kinds are native to the Americas. However, the extinct genus Amphechinus was once found in North America.

Hedgehogs are distantly related to shrews (family Soricidae), and gymnures may be a link between them. Hedgehogs have changed very little over the last 15 million years. Like many mammals, they have adapted to being active at night. Their spiny covering is similar to that of porcupines, which are rodents, and echidnas, a type of monotreme.

Hedgehogs are often brought to wildlife clinics in Europe. They are sensitive and can be easily stressed by people, which can sometimes be dangerous for them. When clinics care for hedgehogs, they recommend keeping them in a dark, airy box with little noise. They also suggest avoiding frequent handling.

Etymology

The name hedgehog came into use around the year 1450. It comes from the Middle English word heyghoge. The first part, heyg or hegge, means 'hedge', because hedgehogs often live in hedgerows. The second part, hoge or hogge, means 'hog', because of the animal's piglike snout. Other names for the hedgehog are urchin and hedgepig.

Description

Hedgehogs are easy to recognize by their spines, which are hollow hairs stiffened with keratin. The spines are not poisonous and are not barbed. Unlike the quills of a porcupine, they do not easily fall out. Young hedgehogs usually lose their spines as adult spines grow in to replace them. This is called "quilling." Spines can also fall out when the animal is sick or very stressed. Hedgehogs are usually brown with pale spine tips. However, leucistic 'blonde' hedgehogs live on the Channel Island of Alderney.

When threatened, hedgehogs roll up into a tight, spiny ball. They tuck in their furry face, feet, and belly. Two large muscles in the back move the quills. Hedgehogs are mostly nocturnal, which means they are active at night. Some species are also active during the day. They sleep for much of the day under bushes, grass, or rocks, or often in dens dug underground. All wild hedgehogs can hibernate. How long they hibernate depends on the temperature, the species, and how much food is available.

Diet

Hedgehogs were once placed in a group called Insectivora, but scientists no longer use this name. They are omnivorous, which means they eat many different kinds of food. They eat insects, snails, frogs and toads, snakes, bird eggs, carrion, mushrooms, grass roots, berries, and melons. Afghan hedgehogs eat berries in early spring, after they wake up from hibernation. Hedgehogs have also been seen eating cat food that people leave outside for pets.

Hibernation

When a hedgehog hibernates, its body temperature drops a lot. It goes from a normal 30–35 °C (86–95 °F) down to 2–5 °C (36–41 °F).

Reproduction and lifespan

A hedgehog's pregnancy lasts 35 to 58 days, depending on the species. Larger species usually have three to four babies at a time, and smaller ones usually have five to six. Sometimes an adult male hedgehog harms newborn males. Newborn hoglets cannot see. Their quills are covered by a thin skin that dries and shrinks over several hours. After it is cleaned off, the quills come out.

Hedgehogs live fairly long lives for their size. In captivity, where they have no predators and are fed a set diet, they live eight to ten years, depending on their size. In the wild, larger species live four to seven years, and some have lived up to 16 years. Smaller species live two to four years in the wild and four to seven years in captivity. For comparison, a mouse lives about two years, and a large rat lives three to five years.

Predators

Hedgehogs have many predators. Forest hedgehogs are mostly hunted by birds, especially owls, and by ferrets. Smaller species, like the long-eared hedgehog, are hunted by foxes, wolves, and mongooses. Hedgehog bones have been found in the leftover pellets of the Eurasian eagle owl.

In Britain, the European badger is a predator in busy farming areas. There are fewer hedgehogs where there are many badgers. Some hedgehog rescue groups will not release hedgehogs into areas where badgers live. Badgers also compete with hedgehogs for food.

Domestication

Main article: Domesticated hedgehog

Most pet hedgehogs are hybrids of the four-toed hedgehog, also called the African pygmy hedgehog, and the smaller North African hedgehog. Some other kinds kept as pets are the long-eared hedgehog and the Indian long-eared hedgehog.

As of 2019, owning a hedgehog as a pet is against the law in the US states of Hawaii, Georgia, Pennsylvania, and California. It is also against the law in New York City, Washington, D.C., and some local areas in Canada. People need a special license to breed them. Most European countries do not have these rules, except Scandinavia. However, they must still control how hedgehogs are bred and sold, based on the Berne Convention on the Conservation of European Wildlife and Natural Habitats. In France and Italy, it is against the law to keep wild hedgehogs as pets.

As invasive species

In places where hedgehogs were brought in, such as New Zealand and the islands of Scotland, they became a pest. They have no natural predators there. In New Zealand, they have harmed many native animals, including insects, snails, lizards, and ground-nesting birds, especially shore birds.

Removing hedgehogs has been hard. Efforts to eliminate them from bird colonies on the Scottish islands of North Uist and Benbecula in the Outer Hebrides led to protests around the world. Removal began in 2003. Some animal welfare groups tried to rescue hedgehogs. By 2007, legal injunctions stopped the killing. In 2008, the work changed to trapping hedgehogs and releasing them on the mainland. In 2022, it was reported that hedgehog numbers in rural Britain had been falling quickly since 2000.

Diseases

Hedgehogs can get many of the same diseases that other mammals get, including cancer, fatty liver disease, and cardiovascular disease. Cancer is very common in hedgehogs. The most common kind is squamous cell carcinoma, which spreads quickly from the bone to the organs. Fatty liver and heart disease are believed to be caused by an unhealthy diet and extra weight. Hedgehogs like to eat foods high in fat and sugar, but their bodies are built for low-fat, protein-rich insects. About ten percent of four-toed hedgehogs develop wobbly hedgehog syndrome.

Hedgehogs are also very likely to get pneumonia. This illness makes it hard to breathe and causes a runny nose. It is caused by the bacterium Bordetella bronchiseptica. Hedgehogs rarely pass a fungal ringworm or dermatophytosis skin infection to people who handle them or to other hedgehogs. This infection is caused by Trichophyton erinacei.

Balloon syndrome

Main article: Balloon syndrome

Hedgehogs can suffer from balloon syndrome. This is a rare condition in which gas gets trapped under the skin after an injury or infection, making the animal puff up. It happens only in hedgehogs because their skin is loose enough to curl up. In 2017, the BBC reported a case at Stapeley's Wildlife Hospital. A male hedgehog there was "almost twice its natural size".

Human influence

Like many small animals that live near people, hedgehogs are often hit by cars when they try to cross roads. In Ireland, hedgehogs are one of the most common mammals killed on roads. Researchers studied roads there and found many hedgehogs had died. They also collected other hedgehog bodies from across the country. More males than females were found. Deaths were highest in late spring and early summer. It is thought that these peaks are linked to the breeding season and to young hedgehogs leaving home to explore on their own.

Research has found more hedgehogs living in cities and towns than in the countryside.

Culinary and medicinal use

People have eaten hedgehogs as food in many cultures. They were eaten in Ancient Egypt, and some recipes from the Late Middle Ages call for hedgehog meat. Hedgehogs were traded across Eurasia and Africa for traditional medicine and witchcraft. In the Middle East, especially among the Bedouins, hedgehog meat was thought to be a medicine for rheumatism and arthritis. People also believed hedgehogs could cure many illnesses, including tuberculosis. In Morocco, people breathed in the smoke of burnt hedgehog skin or bristles to treat fever and other ailments. Hedgehog blood was sold as a cure for ringworm, cracked skin, and warts. Romani people still eat hedgehogs, boiled or roasted, and use their blood and fat as medicine.

In 1981, British publican Philip Lewis created a line of Hedgehog Flavoured Crisps. The flavour was based on the seasonings the Romani used when they cooked hedgehogs. The crisps did not contain any real hedgehog, so the Office of Fair Trading told him to change the name to Hedgehog Flavour Crisps.

Genera and species

See also: List of erinaceids

Hedgehogs in the subfamily Erinaceinae are sorted into five groups called genera. The genera are Atelerix, Erinaceus, Hemiechinus, Mesechinus, and Paraechinus. Each genus has several kinds of hedgehog, called species. The table above lists them.

Society and culture

In stories from many countries, hedgehogs are linked with wisdom in Asia and Europe, and with magic in Africa.

Hedgehogs often come out on top in polls asking "Britain's favourite animal."