Other common names

Other common names of the hedgehog (Erinaceus europaeus) include Western European Hedgehog, European Hedgehog and Northern Hedgehog.

The name ‘hedgehog’ came into use around the year 1450, derived from the Middle English ‘heyghoge’, from ‘heyg’, ‘hegge’ = hedge, because it frequents hedgerows, and ‘hoge’, ‘hogge’ = hog, from its piglike snout. Other folk names include ‘urchin’, ‘hedgepig’ and ‘furze-pig’ [1].

Scientific name and classification

Mammalia – mammals; Insectivores (tree shrews, elephant shrews, and Liptotyphla)
Order Lipotyphla – hedgehogs and moonrats, solenodons, shrews, moles and desmans, golden moles, tenrecs and otter shrews
Erinaceomorpha; Family Erinaceidae – spiny hedgehogs and hairy hedgehogs
Genus Erinaceinae – spiny hedgehogs
Species Erinaceus europaeus

Conservation / protected status

According to The IUCN Red List of Threatened Species, the hedgehog is common and abundant throughout its wide range. Therefore, following the 2008 assessment, the hedgehog is classified as Least Concern (LC).

This species is listed on Appendix III of the Bern Convention. It occurs in a number of protected areas throughout its wide range. It is also legally protected in many countries within its range [2].

The hedgehog is also listed as a Priority Species for conservation action under the UK Biodiversity Action Plan [3], and protected from harm in the UK under Schedule 6 of the Wildlife and Countryside Act 1981 [4]. Under the NERC Act 2006, the hedgehog is categorised as a ‘Species of Principal Importance’ for biodiversity. Listing as a Biodiversity Action Plan priority and ‘Principal Importance’ species reflects concerns that hedgehog numbers are in decline and that some protection should be afforded to hedgehogs habitat through the planning system. This is discussed further below.

Distribution / current and local status

The European Hedgehog is found in most parts of Europe and Asia. There are two geographical races, the western (E. europaeus europaeus), which is the species found in the UK, and over the whole of western Europe, including southern Scandinavia and northern Russia (for European distribution map, see http://www.iucnredlist.org/details/29650/1), and the eastern (E. europaeus roumanicus), which occurs no further west than eastern Germany [5]. The eastern hedgehog has lighter coloured ventral fur and different skull morphology and is sometimes known as the ‘white-breasted hedgehog’. This form is genetically distinct [6] and often classified as a separate species Erinaceus concolor.

The hedgehog is common in parks, gardens and farmland throughout mainland Britain and Ireland. It has also been introduced to many islands including Orkney, Shetland, Isle of Man and some of the Channel Islands [7]. Western European hedgehogs have also been introduced to New Zealand.

The hedgehog is generally a relatively common and widespread species. There is concern that there has been a recent population decline in the UK. The extent of current data, from the Tracking Mammals partnership, using a standardised survey method since 2005, indicates a significant decrease in hedgehog numbers equivalent to a 44% decline over the last 25 years [8]. In 2007 The British Hedgehog Preservation Society (BHPS) launched a national survey ‘Hogwatch’, which suggested a decline in both suburban and rural areas; hedgehogs were more likely to be seen in the east of the UK, which however was the part of the country with a higher rate of hedgehog loss. Hedgehogs were absent from intensively urbanised conurbations and also more sparsely recorded from the south west, including central Devon [9].

The population trend currently listed by the IUCN is ‘stable’ [2]. This does not include island populations which have been introduced and are not considered part of the natural population range.

Hedgehog records in Devon
Hedgehog records in Devon

Devon Biodiversity Records Centre (DBRC) has scattered hedgehog records for most 1km squares in Devon, and they are expected to have a widespread distribution. Overall, hedgehogs are thought to be under-recorded in the county. Records are concentrated in suburban areas (see map), which perhaps reflects to some extent the higher number of active recorders in conurbations. However it is speculated that hedgehogs have higher survival prospects in suburban areas, where there are fewer badgers, which are the hedgehog’s only significant natural predator. Correspondingly it may be that hedgehogs live at a lower population density in agricultural areas where habitat is more fragmented and where there are higher badger populations. There are few records from upland moors such as Dartmoor and the pebblebed heathlands of east Devon, habitats which are regarded as unsuitable for hedgehogs, for reasons described further below.

General Description

The hedgehog is one of the UK’s most instantly recognisable native mammals, as it is the only British mammal to have spines. The European hedgehog is a short, compact mammal with a pointed snout and a short tail.

Body Length: 18-30 cm
Tail: 1.7-5 cm
Rear foot: 3.4-5 cm
Ear: 2-3.5 cm
Body Weight: 600-800 g [5, 6, 11, 12]

Males and females are similar in appearance. Males are sometimes said to be bigger than females but size and weight fluctuate throughout the active season, which means determining the sex of an individual by sight is unreliable without inspecting the hedgehog’s genitalia. Body weight increases from 120 g at weaning, and may sometimes exceed 1000 g towards the hibernation period [6, 11, 12].

The spines are modified hollow hairs made stiff with keratin, construction which is light but also flexible. Hedgehogs are adept at climbing and are known to drop from height while rolled into a ball, using the spines as shock absorbers. Spines are about 22 mm long, pale creamy brown with dark band near tip. There is no seasonal moult, and the spines are long-lasting, replaced irregularly. Individual spines are still present after 18 months [11, 12].

The hedgehog’s spines are not poisonous, nor barbed, and, unlike the quills of a porcupine, are embedded within the skin through muscle attachments, so that they cannot easily be removed from the hedgehog. Through this means a hedgehog is able to bristle its spines and point them directionally towards a threat. Immature hedgehogs undergo a single moult when they shed baby spines and replace them with adult spines. This is called “quilling”. When under extreme stress or during sickness, a hedgehog can also lose spines [1]. Bald hedgehogs have sometimes been bought into hedgehog rescue centres. These are often then kept in captivity, as they would not be expected to survive in the wild without their principal defence.

Habitat

The European hedgehog usually lives in deciduous woodland, woodland edges, hedgerows and grasslands. They also thrive in a variety of man-made habitats including orchards, vineyards, farmland, parks and gardens, including those in urban areas and suburban areas, where grassy areas provide plenty of food for them [2].

It is rarely seen in wetlands or on unsheltered ground [5]. Intensively farmed arable land is probably a poor habitat, as are moorlands, heathlands and dense conifer forests [7]. Acidic soils are generally inhospitable to the hedgehog’s invertebrate earthworm prey. Hedgehogs construct nests from leaves, and it has been suggested that the deciduous tree line may also determine range limits [12].

Behaviour and life History traits

Hedgehogs may live for up to 6 years, or exceptionally to 10 years; over half die before their first birthday and average life expectancy is about 2-3 years [7].

General Behaviour

Hedgehogs are mainly nocturnal, and rarely active during the day. Later in the year hedgehogs active before dusk and after dawn may be trying to build up fat reserves prior to hibernation. Otherwise hedgehogs seen during the day are more likely to be injured or suffering from poisoning or infection. In such cases hedgehog rescue centres can sometimes treat afflicted animals.

Hedgehogs travel large distances while foraging, not uncommonly 2km or more in a night. Radio tracking studies in the 1980s revealed that males travelled further than females, with the range of the male overlapping those of several females. These studies also showed that hedgehogs were not sedentary but that their ranges shifted gradually and progressively through the season. Individuals used several nests within their foraging range and often would not use the same nest on consecutive nights. This means that an individual hedgehog is not likely to remain in permanent residence in a particular domestic garden.

There is little direct interaction between individuals and, apart from when breeding, hedgehogs appear to avoid one another. Hedgehogs do not hold and defend territories, but do keep to a defined area, known as a ‘home range’. There is some suggestion that there may be a hierarchical use of prime feeding areas. If so there is little to indicate what the communication mechanism might be: hedgehogs have a keen sense of smell but there is no obvious pattern shown in where, for example, droppings are deposited [6, 12].

When they are alarmed, hedgehogs protect themselves by rolling up into a defensive ball and effectively fending off any predators [5, 6, 11, 12, 13]. Rolling up is controlled by a powerful muscle band girdling the body, which can be held closed without tiring for protracted periods. When rolled up, only badgers, and in certain locations pine martens, are strong enough to unroll a hedgehog [6, 12]. However this is not the hedgehog’s sole defensive strategy. Hedgehogs are often regarded as slow animals due to their customary slow, crouched, rocking locomotion as they forage, but, if required, hedgehogs can raise themselves up on their legs and run quite swiftly, reaching average speeds of 30-40 metres per minute over short distances [12]. They are able swimmers, sometimes seen crossing rivers. They can climb banks, but may be unable to escape from steep-sided garden ponds [6].

Feeding

Hedgehogs are omnivorous, but diet predominantly consists of invertebrate prey such as insects and their larvae, beetles, slugs, snails, and worms, They find prey by sound and scent and do not rely upon eyesight. However, almost any kind of edible matter will be consumed if available, including carrion. It has been known for hedgehogs to eat lizards and snakes, frogs, moles and young rabbits, but these sorts of prey are not likely to be common food in the wild. Furthermore they may plunder the nests of partridges or pheasants, and will also eat fruits and berries, acorns and oily seeds, roots and fungi occasionally [5, 6, 12, 14]. Experiments carried out with captive hedgehogs showed that although they preferred an animal-based diet e.g. meat, fat, milk, cheese and fish, vegetable foods were also taken. These included cooked potatoes and carrots, radishes, berries and fruits e.g. orange, strawberries, crushed pineapple, dates and pears [14]. It is now well known that traditional milk and bread are not suitable for hedgehog diet, and will tend to give them diarrhoea. Meat, in the form of dog and cat food, and water, are best as supplementary foods [12].

Breeding

The hedgehog’s breeding season generally lasts from April until September, but the main period of activity is usually in May and June when the nights are warm. That is when you are most likely to hear the loud, rhythmic snorting of ‘courting’ hedgehogs. The male circles the female for as much as 20 minutes or more, while the female emits a loud huffing, buffeting the male away unless prepared to mate. There is no evidence of any sort of pair bond between male and female hedgehogs. Sometimes they may pair up with another partner the very same night [6, 12]. Females are usually pregnant for about four and a half weeks and then give birth to up to seven pink, blind young in a nest made of grass and leaves. At birth, the young have short white spines, which they lose within a few weeks when the brown spines grow through. They feed on the mother’s milk and become independent at two months old [13]. Until this time there is some maternal care, and mothers may be seen leading a train of young hedgehogs on foraging expeditions.

In some years it may be possible for hedgehogs to rear two broods during the active season. The later brood needs to acquire sufficient fat reserves to survive hibernation; in weight terms, individuals need to weigh at least 450g. This is when putting out food for hedgehogs in the garden can be of greatest value. Because female hedgehogs may have been raising offspring late into the year, which is energetically demanding, they are often active later than males, as they attempt to gain body weight. Male hedgehogs may then enter into, and emerge from, hibernation, earlier than female hedgehogs [6].

Hibernation

Hedgehogs avoid the coldest times of winter and the absence of prey by hibernating, usually between November and early April, depending on the weather. Prior to hibernation, the hedgehog builds up a store of special brown fat; this is thought to help provide energy to re-activate metabolism when the hedgehog arouses from hibernation. The precise cues for hibernation are not well understood, but day length, food resources and hormone concentrations are thought to contribute. During hibernation, metabolism can slow to 1-2 heart beats per minute. Hedgehogs may wake up several times over winter, occasionally building new hibernation nests in different locations. In the spring they commonly spend a few days being active then enter hibernation again during a cold snap. The winter nest is made of leaves, tucked under a bush or log pile or garden shed, anywhere that offers support and protection [6, 7, 12].

Hedgehogs in the Garden

Short grass such as garden lawns is good feeding habitat for hedgehogs at certain times of year, where earthworms, slugs, beetles and leather jackets can more easily be taken. Hedgehogs prefer to be close to cover. Gardens where there is a mix of shrub cover and open lawn, where pesticides are not used (so that there is an abundance of invertebrate prey), and where there are hedges, instead of fences, to provide nesting spaces and access to other gardens, are among the best places to see hedgehogs.

The hedgehog is known as ‘the gardener’s friend’ as it will eat slugs, caterpillars etc., and does no harm. They make poor pets and should not be kept in captivity, but instead regarded as welcome garden visitors [15]. For more information on how to encourage hedgehogs into your garden, visit the website of British Hedgehog Preservation Society, http://www.britishhedgehogs.org.uk .

Piles of leaves and undisturbed corners, with logpiles or other materials under which to construct a nest, may encourage hedgehogs to nest in your garden.

Predators and other threats

The hedgehog’s spines usually provide adequate protection against most predators, though a few young or sickly animals may be killed by foxes, badgers and dogs. Badgers are thought to be a main predator of hedgehogs, and have been shown to exclude them from areas that are otherwise suitable [16]. In certain areas very occasionally hedgehogs may be taken by polecat, tawny owl and golden eagle.

Large numbers are killed on roads, though the main cause of mortality is insufficient fat reserves having been built up prior to hibernation. Many effectively starve to death during hibernation, especially during their first winter. Hedgehogs can swim but will drown in garden ponds if there is no means to climb out [11], so always ensure that there are several gently sloping slipways to allow them to escape if they fall in [15]. They are sometimes injured by strimmers and lawnmowers, so check long grass before cutting.

If you encourage hedgehogs into your garden they will eat the slugs. Slug pellets are widely regarded as a hazard, though this has not been proven. The threat may not only be by build-up of active chemicals in prey items, but also by indiscriminately destroying most of the hedgehog’s natural food. Metaldehyde and aluminium sulphate are the most common active ingredients; metaldehyde soon breaks down into compounds such as water, so it is difficult to attribute symptoms directly to these sorts of pesticides. Anecdotally, hedgehogs suffering from slug pellet poisoning show symptoms of disorientation, drunkenness, and dehydration, sometimes seen wandering aimlessly in the open during the day. Hedgehog rescue centres may be able to treat these casualties.

Bonfires can sometimes conceal a sleeping hedgehog, so check underneath before igniting. Litter is also dangerous to hedgehogs, whose spines can become entangled in plastic rings that hold cans together, or become wedged in yoghurt pots or empty tins. Dispose of litter carefully and squash all your tin cans before recycling them [15].

Notwithstanding all these hazards, the biggest threat to hedgehogs is habitat loss. Over the last 30 years, agriculture has favoured large fields and the habitats of the hedgehog, particularly hedges, have been removed. Agricultural pesticide usage also puts further pressure on hedgehog populations. With more hedgehog-friendly gardens however, the mammal’s future should be fairly secure [17].

Anecdotes and quirky facts

A little understood behaviour is ‘self-anointing’, when an individual covers itself in saliva, frothed up into a lather. This seems to be triggered on encountering certain, often tart or acidic, tastes or smells. The trigger object is repeatedly licked to build up a lather, then the hedgehog covers its coat with the froth. There is a broad list of items recorded as triggering self-anointing, including leather, nylon stockings, furniture polish, cigars, distilled water, leaves, and a toad [14]. The reason for the behaviour is unknown; some suggestions are that it relieves irritation from parasites, helps broadcast the individual’s scent, offers an additional chemical defence, or is some sort of display [6]. The behaviour has been seen mostly in captive hedgehogs, though is suspected to happen, just unobserved, in the wild. Most hedgehogs seem not to self-anoint (studies of captive hedgehogs suggest no more than 10-11%), though it has been seen in both sexes, sub-adults, and still-blind nestlings [6]. Self-anointing is strongly associated with stimulation of the Jacobson’s olfactory organ (which is the organ stimulated in cats when they purr), but this is about all that is known.

Introduced hedgehogs have become implicated as a serious pest in the Western Isles of Scotland, where they are suspected of eating the eggs of ground-nesting waders such as Snipe, Dunlin, Redshank and Lapwing. A programme of attempted eradication was carried out, on the basis that hedgehog translocation would not be successful and would cause undue suffering to translocated animals. Scientific studies demonstrated that this was unfounded, and the eradication programme was stopped [18].

This case is described in more detail in A prickly affair: my life with hedgehogs by Hugh Warwick (2008). The research paper is downloadable from:

H Warwick, P Morris & D Walker (2006) Survival and weight changes of hedgehogs (Erinaceus europaeus) translocated from the Hebrides to Mainland Scotland Lutra 49 (2) 89-102
http://www.urchin.info/images/Lutra_49_2_Warwick_et_al.pdf

The hedgehog is also considered a pest in New Zealand where it preys upon the native giant snails (Powelliphanta), weta and various other native invertebrates [1].

Rare albino and blond hedgehogs are known. Blond hedgehogs have a recessive gene, which gives rise to beady, button-black eyes and creamy-coloured spines; they are not strictly speaking albino. They are extremely uncommon except on the Channel Island of Alderney where they are nicknamed “Alderney Spike Girls”. Approximately 1000 blond hedgehogs are thought to exist there, making up ~10-15% of the Alderney population. They allegedly carry no fleas, and are a localised island variant of Erinaceus europaeus [1].

Local studies

Most records of hedgehogs in Devon have come from incidental reports to the Devon Biodiversity Records Centre. Devon Wildlife Trust included the hedgehog in its garden wildlife survey in 2006-8; otherwise there have been few systematic targeted surveys in the county.

The survival of rehabilitated and translocated hedgehogs from rescue centres was studied on sites across the mid-Devon and Somerset border in the early 1990s. This is described in more detail in A prickly affair: my life with hedgehogs by Hugh Warwick (2008).

In Ogwell, near Newton Abbot, is Prickly Ball Farm hedgehog hospital, which has been developed into a visitor centre for British wildlife, following work as a hedgehog rescue centre. The original owners have since joined Animals in Distress, a wildlife rescue charity with a local base across the Newton Abbot and Torbay area, which continues to carry out hedgehog rescue work.

http://www.pricklyballfarm.com/
http://www.animalsindistress.uk.com/index.php

Field signs and sending in records

Hedgehogs are thought to be under-recorded and, due to concerns about a possible decline, all new hedgehog records are welcomed by Devon Biodiversity Records Centre. Records can be validated on the basis of:

  • Sightings Hedgehogs are not likely to be confused with other mammal species. Records from garden sightings and road casualties are of value.
  • Droppings Hedgehog droppings are irregularly cylindrical, approximately 25mm long x 7-8 mm wide, black-grey, dry and often shiny and bumpy with the packed indigestible chitinous remains of insects (legs, exoskeletons, beetle wing cases) and worm bristles protruding. There is no apparent pattern to where droppings are deposited, though they are more likely to be found in open areas such as lawns, not too far from cover, along the routes where hedgehogs forage.
  • FootprintsForefeet are ~2.5cm long, with four toes in a row and one toe set slightly further back; the hind feet are quite different, narrower and longer (~3-4cm), with three toes in a row and two set a little further back. This means that two different tracks are produced by the fore and hind feet. Unambiguous tracks are not very frequently seen and unless very clear, other evidence should be sought to corroborate presence.
  • Nests If you find a nest try not to disturb it. Disturbing a breeding nest may result in the mother abandoning the nestlings. Nests typically comprise a dense compact dome of leaves 30-60cm in diameter, often braced under some overhanging springy vegetation. In gardens, nests may be situated under sheds, branches, logpiles, at the foot of the hedge or among piles of leaves.

References, bibliography and links

[1] Wikipedia – The Free Encyclopedia
http://en.wikipedia.org/wiki/Hedgehog
http://en.wikipedia.org/wiki/Erinaceus_Europaeus

[2] The IUCN Red List of Threatened Species http://www.iucnredlist.org/details/29650/1

[3] UK Biodiversity Action Plan http://www.ukbap.org.uk/PrioritySpecies.aspx?group=8

[4] P Morris (1993) A Red Data Book for British Mammals The Mammal Society, Bristol

[5] Mathew M Vriends PhD. & Tanya M Heming-Vriends (2000) Hedgehogs, Barron’s, Hauppauge, NY

[6] Nigel Reeve (1994) Hedgehogs T & A D Poyser Natural History, London

[7] The Mammal Society – Mammal Fact Sheets http://www.mammal.org.uk/index.php?option=com_content&view=article&id=212&Itemid=245

[8] Tracking Mammals Partnership Update 2009 www.trackingmammals.org

[9] Hog watch survey report 2007 British Hedgehog Preservation Society/People’s Trust for Endangered Species www.HogWatch.org.uk

[10] Devon Biodiversity Records Centre – Data Search 2009

[11] GB Corbet & HN Southern (1977) The Handbook of British Mammals Blackwell, London

[12] Pat Morris (2006) The new hedgehog book Whittet Books, Stowmarket

[13] People’s Trust for Endangered Species – Mammal Fact Files http://www.ptes.org/index.php?cat=84

[14] Maurice Burton (1969) The Hedgehog Survival Books 9, Andre Deutsch

[15] British Hedgehog Preservation Society – Leaflets and FAQs http://www.britishhedgehogs.org.uk/FAQS/general.htm

[16] CP Doncaster (1992) Testing the role of intraguild predation in regulating hedgehog  populations Proceedings of the Royal Society of London B 249:113-117. Quoted in N. Reeve (1994) Hedgehogs T&AD Poyser Natural History, London

[17] The Wildlife Trusts
http://www.wildlifetrusts.org/index.phpsection=environment:species:mammal&id=203
http://www.wildlifetrust.org.uk/facts/hedge.htm

[18] Hugh Warwick (2008) A prickly affair: my life with hedgehogs Allen Lane, London

Links

ARKive hedgehog http://www.arkive.org/hedgehog/erinaceus-europaeus/

BAP hedgehog http://www.ukbap.org.uk/PrioritySpecies.aspx?group=8

British Hedgehog Preservation Society http://www.britishhedgehogs.org.uk/

People’s Trust for Endangered Species http://www.ptes.org/

HogWatch http://www.hogwatch.org.uk/

PTES Mammals on roads http://www.ptes.org/index.php?cat=64

Prickly Ball Farm Hedgehog Hospital and British Wildlife Garden Centre
Denbury Rd
Ogwell
Newton Abbot
Devon
TQ12 6BZ
tel. 01626 362319
http://www.pricklyballfarm.com/
e-mail enquiries@pricklyballfarm.co.uk

 

Devon Wildlife Hospital: www.devonwildlifehospital.com/info.html
Hedgehog helpline 01626 324830 or 07730 844954