A hedgehog is a spiny mammal of the subfamily Erinaceinae, in the family Erinaceidae. There are 17 species of hedgehog in five genus found throughout parts of Europe, Asia, and Africa, and in New Zealand by introduction. There are no hedgehogs native to Australia and no living species native to the Americas. However, the extinct genus Amphechinus was once present in North America.
Hedgehogs share distant ancestry with (family Soricidae), with possibly being the intermediate link, and they have changed little over the last 15 million years. Like many of the first mammals, they have adapted to a nocturnal way of life. Their spiny protection resembles that of , which are rodents, and , a type of monotreme.
Hedgehogs roll into a tight spiny ball when threatened, tucking in the furry face, feet, and belly. The hedgehog's back contains two large muscles that direct the quills. Some light-weight desert hedgehog species with fewer spines are more likely to flee or attack, ramming an intruder with the spines, rolling up only as a last resort.
Hedgehogs are primarily nocturnal, with some species also active during the day. Hedgehogs sleep for a large portion of the day under bushes, grasses, rocks, or most commonly in dens dug underground. All wild hedgehogs can hibernation, though the duration depends on temperature, species, and abundance of food.
Hedgehogs are fairly vocal, with a variety of grunts, snuffles and/or squeals.
They occasionally perform a ritual called anointing. 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 Viperidae 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, Wild boar, , , and hedgehogs all have mutations in the nicotinic acetylcholine receptor that prevent the binding of the snake venom α-neurotoxin.
The Olfactory system has been little studied in the hedgehog, as the olfactory part of the mammal brain is obscured inside the Neocortex. Tests have suggested that hedgehogs share the same olfactory electrical activity as cats.
Hedgehogs have a relatively long lifespan for their size. In captivity, lack of predators and controlled diet contribute to a lifespan of eight to ten years depending on size. In the wild, larger species live four to seven years (some recorded up to 16 years), and smaller species live two to four years (four to seven in captivity). This compares to a mouse at two years and a large rat at three to five years.
Newborn hoglets are blind, with their quills covered by a protective membrane which dries and shrinks over several hours, Litter – Burlington and MIDI (2004-04-19) . hamorhollow.com and falls off after cleaning, allowing the quills to emerge.
In Britain, a predator in intensively farmed areas is the European badger with populations lower in areas with many badgers. Some hedgehog rescue societies will not release hedgehogs into known badger territories. Where have all the hedgehogs gone ? . Snufflelodge.org.uk. Retrieved 2013-09-05. Badgers also compete with hedgehogs for food.
, it is illegal to own a hedgehog as a pet in the US states of Hawaii, Georgia, Pennsylvania, and California, as well as in New York City, Washington, D.C. and some Canadian municipalities. Breeding licenses are required. No such restrictions exist in most European countries with the exception of Scandinavia. In Italy, it is illegal to keep wild hedgehogs as pets.
Eradication can be troublesome. Attempts to eliminate hedgehogs from bird colonies on the Scottish islands of North Uist and Benbecula in the Outer Hebrides were met with international protest. Eradication began in 2003 with 690 hedgehogs killed, though animal welfare groups attempted rescues. By 2007, injunction prohibited the killing, and in 2008, the elimination process was changed to trapping and releasing on the mainland.
In 2022, it was reported that the hedgehog population in rural Britain was declining rapidly, down by 3075% since 2000.
Cancer is very common in hedgehogs. The most common is squamous cell carcinoma, which spreads quickly from bone to the organs, unlike in humans. Surgery to remove the bone tumors is impractical.
Fatty liver and heart disease are believed to be caused by an unhealthy diet and obesity. Hedgehogs will eagerly eat foods high in fat and sugar, despite a metabolism adapted for low-fat, protein-rich insects.
Hedgehogs are also highly susceptible to pneumonia, with difficulty breathing and nasal discharge, caused by the bacterium Bordetella bronchiseptica.
Hedgehogs uncommonly transmit a fungal ringworm or dermatophytosis skin infection to human handlers and other hedgehogs, caused by Trichophyton erinacei, a distinct mating group among the Arthroderma benhamiae fungi.
Hedgehogs can suffer from balloon syndrome, a rare condition in which gas is trapped under the skin from injury or infection, causing the animal to inflate. The condition is unique to hedgehogs because their skin is baggy enough to curl up. In 2017, the BBC reported a case of a male hedgehog "almost twice its natural size, literally blown up like a beach ball with incredibly taut skin". At Stapeley's Wildlife Hospital, vet Bev Panto, said, "I have seen three or four of these cases and they are very strange every time and quite shocking ... When you first see them they appear to be very big hedgehogs but when you pick them up they feel so light because they are mostly air". The British Hedgehog Preservation Society advises:
In 1981, British publican Philip Lewis developed a line of Hedgehog Flavoured Crisps, whose taste was apparently based on the flavourings used by Romani to bake hedgehogs. As they did not contain any actual hedgehog product, the Office of Fair Trading ordered him to change the name to Hedgehog Flavour Crisps.
The hedgehog routinely tops ‘Britain’s favourite animal’ polls. Beastly Britain review at The Guardian, 27 Jun 2025
Diet
Hibernation
Reproduction and lifespan
Predators
Domestication
As invasive species
Diseases
There is no single cause for this condition. The air can be removed by incising or aspirating through the skin over the back. Antibiotic cover should be given. This may be associated with lung/chest wall damage or a small external wound acting like a valve or a clostridium type infection.
Human influence
Culinary and medicinal use
Genera and species
Society and culture
See also
External links
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