A hedgehog is any of the spiny mammals of the subfamily Erinaceinae, which is in order
Erinaceomorpha.
There are seventeen species of hedgehog in five genera, found through parts of Europe,
Asia, Africa and New Zealand.
There are no hedgehogs native to Australia, and no living species native to the Americas.
Hedgehogs share distant ancestry with shrews, with gymnures possibly being the intermediate
link, and have changed little over the last 15 million years.
Like many of the first mammals, they have adapted to a nocturnal, insectivorous way
of life.
Hedgehogs' spiny protection resembles that of the unrelated rodent porcupines and monotreme
echidnas.
The name hedgehog came into use around the year 1450, derived from the Middle English
heyghoge, from heyg, hegge, because it frequents hedgerows, and hoge, hogge, from its piglike
snout.
Other names include urchin, hedgepig and furze-pig.
The collective noun for a group of hedgehogs is array or prickle.
Physical description Hedgehogs are easily recognized by their spines,
which are hollow hairs made stiff with keratin.
Their spines are not poisonous or barbed and, unlike the quills of a porcupine, cannot easily
be removed from the hedgehog.
However, spines normally come out when a hedgehog sheds baby spines and replaces them with adult
spines.
This is called "quilling".
When under extreme stress or during sickness, a hedgehog can also lose spines.
A defense that all species of hedgehogs possess is the ability to roll into a tight ball,
causing all of the spines to point outwards.
However, its effectiveness depends on the number of spines, and since some of the desert
hedgehogs evolved to carry less weight, they are much more likely to try to run away and
sometimes even attack the intruder, trying to ram into the intruder with its spines;
rolling up into a spiny ball is used by those species as a last resort.
There are a different number of predators for different species: while forest hedgehogs
have relatively few predators, primarily birds and ferrets, smaller species like the long-eared
hedgehog are preyed on by foxes, wolves and mongooses.
Hedgehogs are primarily nocturnal, although, depending on the species, they may be more
or less active during the day.
The hedgehog sleeps for a large portion of the daytime either under cover of bush, grass,
rock or in a hole in the ground.
Again, different species can have slightly different habits, but in general hedgehogs
dig dens for shelter.
All wild hedgehogs can hibernate, although not all do; hibernation depends on temperature,
species, and abundance of food.
The hedgehog's back is made up of two large muscles, which control the positioning of
its quills.
There are about 5,000 to 6,500 quills on the average hedgehog, and these are strong on
the outer surface, but filled with air pockets on the inside.
The hedgehog uses its quills to protect itself from predators, using muscles which draw their
quilled skin to cover their full body, and pulling in the parts of their bodies not covered,
such as their head, feet, and belly.
This form of defense is the hedgehog's most successful, but is usually their last resort.
Hedgehogs are fairly vocal and communicate through a combination of grunts, snuffles
and/or squeals, depending on species.
Hedgehogs 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.
The specific purpose of this ritual is unknown, but some experts believe anointing camouflages
the hedgehog with the new scent of the area and provides a possible poison or source of
infection to predators poked by their spines.
Anointing is sometimes also called anting because of a similar behavior in birds.
Similar to opossums, mice and moles, hedgehogs have some natural immunity against snake venom
due to the protein erinacin in the animal's muscular system.
Diet
Although traditionally classified in the now abandoned order Insectivora, hedgehogs are
not exclusively insectivores but are almost omnivorous.
Hedgehogs feed on insects, snails, frogs and toads, snakes, bird eggs, carrion, mushrooms,
grass roots, berries, melons and watermelons.
Berries constitute a major part of an Afghan hedgehog's diet in early spring after hibernation.
Reproduction and lifespan
Depending on the species, the gestation period is 35–58 days.
The average litter is 3–4 newborns for larger species and 5–6 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.
Larger species of hedgehogs live 4–7 years in the wild, and smaller species live 2–4
years, compared to a mouse at 2 years and a large rat at 3–5 years.
Lack of predators and controlled diet contribute to a longer lifespan in captivity.
Hedgehogs are born blind.
The hedgehogs are birthed with a protective membrane covering their quills, which dries
and shrinks over the next several hours.
The infants are born with quills beneath the skin, like pimples, and pass the skin after
they have been cleaned.
Predators Hedgehog bones have been found in the pellets
of the European Eagle Owl.
In Britain, the main predator is the badger.
Hedgehogs in the UK have demonstrably lower populations in areas where badgers are numerous,
so that British hedgehog rescue societies will not release hedgehogs into known badger
territories.
Domesticated hedgehogs
The most common pet species of hedgehog are hybrids of the white-bellied hedgehog or four-toed
hedgehog and the North African hedgehog.
It is smaller than the European hedgehog, and thus is sometimes called the African pygmy
hedgehog.
Other species kept as pets are the long-eared hedgehog and the Indian long-eared hedgehog.
It is illegal to own a hedgehog as a pet in some US states and some Canadian municipalities,
and breeding licenses are required.
No such restrictions exist in most European countries with the exception of Scandinavia.
However, in the UK wild hedgehogs are considered endangered and it is illegal to keep one as
a pet.
Invasive species In areas where hedgehogs have been introduced,
such as New Zealand and the islands of Scotland, the hedgehog itself has become a pest.
In New Zealand it causes immense damage to native species including insects, snails,
lizards and ground-nesting birds, particularly shore birds.
As with many introduced animals, it lacks natural predators.
With overpopulation, it kills off more insects than initially intended and expands its diet
to include things such as snails, worms and the eggs of wading birds.
Correcting overpopulation is troublesome itself.
Attempts to eliminate hedgehogs from bird colonies on the Scottish islands of North
Uist and Benbecula in the Outer Hebrides were met with international outrage.
Eradication began in 2003 with 690 hedgehogs being killed.
Animal welfare groups attempted rescues to save the hedgehogs.
By 2007, legal injunctions against the killing of hedgehogs were put in place.
In 2008, the elimination process was changed from killing the hedgehogs to trapping them
and releasing on the mainland.
Diseases Hedgehogs suffer many diseases common to humans.
These include cancer, fatty liver disease and cardiovascular disease.
Cancer is very common in hedgehogs.
The most common is squamous cell carcinoma.
Squamous cell spreads quickly from the bone to the organs in hedgehogs, unlike in humans.
Surgery to remove the tumors is rare because it would result in removing too much bone
structure.
Fatty liver disease is believed by many to be caused by bad diet.
Hedgehogs will eagerly eat foods that are high in fat and sugar.
Having a metabolism adapted for low-fat, protein-rich insects, this leads to common problems of
obesity.
Fatty liver disease is one sign, heart disease is another.
Hedgehogs uncommonly transmit a characteristic fungal skin infection to human handlers as
well as other hedgehogs.
This ringworm or dermatophytosis infection is caused by Trichophyton erinacei, which
forms a distinct mating group within the Arthroderma benhamiae species complex.
Human influence
As with most small mammals living around humans, cars pose a great threat to hedgehogs.
Many are run over as they attempt to cross roadways.
In 2006, McDonald's changed the design of their McFlurry containers to be more hedgehog-friendly.
Previously, hedgehogs would get their heads stuck in the container as they tried to lick
the remaining food from inside the cup.
Then, being unable to get out, they would starve to death.
Domesticated hedgehogs display this behavior by getting their head stuck in tubes and walking
around with the tube on their head.
Hedgehog owners often refer to this as "tubing" and promote the behavior by supplying clean
tubes.
Most owners are considerate enough, however, to cut the tubes lengthwise so as to prevent
the hedgehog from remaining trapped against their will.
Curiously though, some will still knowingly get themselves stuck for a few hours.
Culinary and medicinal use Hedgehogs are a food source in many cultures.
Hedgehogs were eaten in Ancient Egypt and some recipes of the Late Middle Ages call
for hedgehog meat.
In the Middle East and especially among Bedouins, hedgehog meat is considered medicinal, and
thought to cure rheumatism and arthritis.
Romani people still eat hedgehogs, boiled or roasted, and also use the blood and the
fat for its supposed medicinal value.
During the 1980s, "hedgehog-flavour" crisps were introduced in Britain, although the product
did not contain any hedgehog.
Genera and species
Subfamily Erinaceinae Genus Atelerix
Four-toed hedgehog, Atelerix albiventris North African hedgehog, Atelerix algirus
Southern African hedgehog, Atelerix frontalis Somali hedgehog, Atelerix sclateri
Genus Erinaceus Amur hedgehog, Erinaceus amurensis
Southern white-breasted hedgehog, Erinaceus concolor
European hedgehog, Erinaceus europaeus Northern white-breasted hedgehog, Erinaceus
roumanicus
Genus Hemiechinus Long-eared hedgehog, Hemiechinus auritus
Indian long-eared hedgehog, Hemiechinus collaris
Genus Mesechinus Daurian hedgehog, Mesechinus dauuricus
Hugh's hedgehog, Mesechinus hughi
Genus Paraechinus Desert hedgehog, Paraechinus aethiopicus
Brandt's hedgehog, Paraechinus hypomelas Indian hedgehog, Paraechinus micropus
Bare-bellied hedgehog, Paraechinus nudiventris
See also European hedgehog
Echidnas or "spiny anteaters", members of the order Monotremata that have spines
Hedgehog's dilemma Hedgehogs in culture
Porcupines, two different rodent families which have spines or quills
References
External links Hedgehogs at DMOZ
Hedgehog reference at the University of Michigan Museum of Zoology
Hedgehog facts Hedgehog care and advice
Natural History of European Hedgehogs "Hedgehog".
Encyclopedia Americana. 1920.