A hedgehog is a spinymammal of the subfamilyErinaceinae, in theeulipotyphlan familyErinaceidae. There are 17 species of hedgehog in fivegenera 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 genusAmphechinus was once present in North America.
Hedgehogs share distant ancestry withshrews (family Soricidae), withgymnures possibly being the intermediate link, and they have changed little over the last 15 million years.[2] Like many of the first mammals, they have adapted to a nocturnal way of life.[3] Their spiny protection resembles that ofporcupines, which are rodents, andechidnas, a type ofmonotreme.
Etymology
The namehedgehog came into use around the year 1450, derived from theMiddle Englishheyghoge, fromheyg,hegge'hedge', because it frequentshedgerows, andhoge,hogge'hog', from its piglike snout.[4] Other names that are used areurchin[5] andhedgepig.[6]
Description
Hedgehogs are easily recognized by theirspines, which are hollow hairs made stiff withkeratin.[7] Their spines are notpoisonous orbarbed and, unlike the quills of aporcupine, do not easily detach from their bodies. However, the immature animal's spines normally fall out as they are replaced with adult spines. This is called "quilling". Spines can also shed when the animal is diseased or under extreme stress. Hedgehogs are usually brown, with pale tips to the spines, though blonde hedgehogs are found on the Channel Island ofAlderney.
A skin-skeletal preparationClose-up of the last 5 millimetres (0.20 in) of a hedgehog spine (SEM microscopy)A hedgehog that feels threatened can roll into a tight ball.
Hedgehogs roll into a tight spiny ball when threatened, tucking in the furry face, feet, and belly.[7] 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 primarilynocturnal, 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 canhibernate, 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 calledanointing.[8] 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 itsspines with itstongue. Some experts believe this might serve tocamouflage the hedgehog with the local scent, and might also lead to infection of predators poked by the spines. Anointing is sometimes also calledanting after a similar behavior in birds.
Thesense of smell has been little studied in the hedgehog, as the olfactory part of the mammal brain is obscured inside theneopallium. Tests have suggested that hedgehogs share the same olfactory electrical activity as cats.[11]
When a hedgehog hibernates, its normal 30–35 °C (86–95 °F) body temperature decreases to 2–5 °C (36–41 °F).[12]
Reproduction and lifespan
Hedgehoggestation lasts 35–58 days, depending on species. The average litter is three to four newborns for larger species and five to six for smaller ones. As with many animals, it is not unusual for an adult male hedgehog to kill newborn males.
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 incaptivity). This compares to a mouse at two years and a largerat at three to five years.
Newborn hoglets are blind, with their quills covered by a protective membrane which dries and shrinks over several hours,[13] and falls off after cleaning, allowing the quills to emerge.[14]
In Britain, a predator in intensively farmed areas is theEuropean badger with populations lower in areas with many badgers.[16] Some hedgehog rescue societies will not release hedgehogs into known badger territories.[17] Badgers also compete with hedgehogs for food.[18]
As of 2019[update], it is illegal to own a hedgehog as a pet in the US states ofHawaii,Georgia,Pennsylvania, andCalifornia,[20] as well as inNew York City,Washington, D.C. and some Canadian municipalities. Breeding licenses are required. No such restrictions exist in most European countries with the exception ofScandinavia. InItaly, it is illegal to keep wild hedgehogs as pets.[21]
As invasive species
In areas where hedgehogs have been introduced,such as New Zealand and the islands ofScotland, the hedgehog has become a pest, lacking natural predators. In New Zealand it has decimated native species including insects,snails, lizards and ground-nesting birds, particularly shore birds.[22]
Eradication can be troublesome. Attempts toeliminate hedgehogs from bird colonies on the Scottish islands ofNorth Uist andBenbecula in theOuter Hebrides were met with international protest. Eradication began in 2003 with 690 hedgehogs killed, though animal welfare groups attempted rescues. By 2007,legal injunctions prohibited the killing, and in 2008, the elimination process was changed to trapping and releasing on the mainland.[23]
In 2022, it was reported that the hedgehog population in rural Britain was declining rapidly, down by 30–75% since 2000.[24]
Cancer is very common in hedgehogs. The most common issquamous 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.[citation needed]
Hedgehogs are also highly susceptible to pneumonia, with difficulty breathing and nasal discharge,[27] caused by the bacteriumBordetella bronchiseptica.[28]
Hedgehogs uncommonly transmit a fungalringworm ordermatophytosis skin infection to human handlers and other hedgehogs, caused byTrichophyton erinacei, a distinct mating group among theArthroderma benhamiae fungi.[29]
Hedgehog suffering from balloon syndrome before deflating
Hedgehogs can suffer fromballoon 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.[30] In 2017, theBBC reported a case of a male hedgehog "almost twice its natural size, literally blown up like a beach ball with incredibly taut skin".[31][32] AtStapeley'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".[30] The British Hedgehog Preservation Society advises:
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.[33]
Human influence
As with most small mammals living around humans, many arerun over as they attempt to cross roadways. InIreland, hedgehogs are one of the most common mammalian road fatalities. Between April 2008 and November 2010 on two stretches of road measuring 227 km and 32.5 km, there were 133 recorded hedgehog fatalities. Of another 135 hedgehog carcasses collected from throughout Ireland, there were significantly more males than females collected, with peaks in male deaths occurring in May and June. Female deaths outnumbered males only in August, with further peaks in female deaths observed in June and July. It is suggested that these peaks are related to the breeding season (adults) and dispersal/exploration following independence.[34]
Research has documented higher densities of hedgehogs in urban environments compared to rural areas.[35][36]
Culinary and medicinal use
Hedgehogs are a food source in many cultures. They were eaten inAncient Egypt and some recipes of theLate Middle Ages call for hedgehog meat.[37] They are traded throughout Eurasia and Africa for traditional medicine and witchcraft. In the Middle East and especially amongBedouins, hedgehog meat is considered medicine againstrheumatism andarthritis.[38] Hedgehogs are also said to cure a variety of disorders fromtuberculosis to impotence. InMorocco, inhaling the smoke of the burnt skin or bristles supposedly remedies fever, impotence, and urinary illnesses; the blood is sold as a cure forringworm, cracked skin andwarts, and the flesh is eaten as a remedy for witchcraft.[39]Romani people still eat hedgehogs, boiled or roasted, and also use the blood and the fat as a medicine.[40]
In 1981, British publican Philip Lewis developed a line ofHedgehog Flavoured Crisps, whose taste was apparently based on the flavourings used by Romani to bake hedgehogs.[41][42] As they did not contain any actual hedgehog product, theOffice of Fair Trading ordered him to change the name to Hedgehog Flavour Crisps.[43]
Hedgehog amulet from Ancient Egypt, New Kingdom, Dynasty 18. Steatite. Cleveland Museum of Art. 1391 BCE to 1353 BCE
Ceramic rhyton in the form of a hedgehog. Mycenaean. 14th to 13th century BCE
Hedgehog sculpture. Faience. Ancient Egypt, Thebes. 1991 BCE to 1778 BCE
^Omori-Satoha, Tamotsu; Yoshio Yamakawab; Dietrich Mebs (November 2000). "The antihemorrhagic factor, erinacin, from the European hedgehog (Erinaceus europaeus), a metalloprotease inhibitor of large molecular size possessing ficolin/opsonin P35 lectin domains".Toxicon.38 (11):1561–80.Bibcode:2000Txcn...38.1561O.doi:10.1016/S0041-0101(00)00090-8.PMID10775756.
^Drabeck, D.H.; Dean, A.M.; Jansa, S.A. (1 June 2015). "Why the honey badger don't care: Convergent evolution of venom-targeted nicotinic acetylcholine receptors in mammals that survive venomous snake bites".Toxicon.99:68–72.Bibcode:2015Txcn...99...68D.doi:10.1016/j.toxicon.2015.03.007.PMID25796346.
^Graesser, Donnasue; Spraker, Terry R.; Dressen, Priscilla; Garner, Michael M.; Raymond, James T.; Terwilliger, Gordon; Kim, Jung; Madri, Joseph A. (January 2006). "Wobbly hedgehog syndrome in African pygmy hedgehogs. (Atelerix spp.)".Journal of Exotic Pet Medicine.15 (1):59–65.doi:10.1053/j.jepm.2005.11.010.
^Hubert, P., Julliard, R., Biagianti, S., & Poulle, M. L. (2011). "Ecological factors driving the higher hedgehog (Erinaceus europeaus) density in an urban area compared to the adjacent rural area".Landscape and Urban Planning.103 (1):34–43.Bibcode:2011LUrbP.103...34H.doi:10.1016/j.landurbplan.2011.05.010.{{cite journal}}: CS1 maint: multiple names: authors list (link)
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