Animal Diversity Web

Diversity

In the family Erinaceidae, there are 2 subfamilies comprising 10 genera. The woodland hedgehog genus, Erinaceus, falls under subfamily Erinaceinae and is composed of four species: Erinaceus europaeus, Erinaceus roumanicus, Erinaceus amurensis, and Erinaceus concolor. The most commonly known species is E. europaeus, of which more information is readily available, but all hedgehog species in this genus share similar characteristics. Woodland hedgehogs are small to medium-sized mammals that are nocturnal and well-known for the coat of protective spines covering their dorsal side. These solitary, opportunistic omnivores can travel up to 2 kilometers every night in search of food or mates in temperate forest, scrubland, and grassland habitats. They are also unique in their preference for urban and suburban habitats, foraging for food in backyard gardens and spending their winters in hibernacula in neighborhoods and parks. Recent declines in woodland hedgehog populations due to car collisions, badger predation, parasites, and habitat fragmentation have sparked research and conservation efforts, but implications of woodland hedgehogs being vectors for zoonotic diseases and ectoparasites have raised other concerns as well. (Amori, et al., 2021; "Invasive Species Compendium", 2010; Černá Bolfíková, et al., 2020; Dunning, 2019; Dziemian, et al., 2014; Hof, et al., 2019; Johnson, 2015; Rasmussen, et al., 2019; Rautio, et al., 2016)

Geographic Range

All four species of Erinaceus can be found in the Palearctic region, although the species vary widely in distribution with little overlap. Amur hedgehogs (E. amurensis) are found in East Asia and western European hedgehogs (E. europaeus) are endemic to Europe. Northern white-breasted hedgehogs (E. roumanicus) are common in Europe and European Russia, while southern white-breasted hedgehogs (E. concolor) are found in the Mediterranean region. Woodland hedgehogs have been introduced to various European countries and isles as well as New Zealand for slug/snail pest control. Despite being known to exhibit wide home ranges and high dispersal rates, woodland hedgehogs' ranges have become increasingly limited by growth in predatory badger (Meles meles) populations and habitat fragmentation due to agricultural and infrastructural expansion. This is especially prevalent regarding increases in roads and fencing. Additionally, recent climate change effects have caused woodland hedgehogs to exhibit oscillating ranges, as they are very sensitive to temperature, humidity, and resource availability. (Amori, et al., 2021; "Invasive Species Compendium", 2010; Černá Bolfíková, et al., 2020; Dunning, 2019; Dziemian, et al., 2014; Johnson, 2015)

• Biogeographic Regions
• palearctic
  • introduced
  • native
• ethiopian
  • introduced
  • native
• oceanic islands
  • introduced

Habitat

Woodland hedgehogs are found in temperate terrestrial habitats, including mixed deciduous and coniferous forests, grasslands, and shrublands. Research has found that woodland hedgehogs prefer hedgerows and edge habitats along forests and grasslands, but they also require relatively large, accessible habitats. This is due to their wide home ranges as they forage and/or search for mates during the breeding season. They can be found in lowlands and hills but have also been spotted in mountainous environments, albeit rarely. What is most important in determining woodland hedgehogs' habitats is resource availability of food (particularly insects) and nesting supplies such as leaf litter, bramble, nettles, and similar material. Suitable nests are often characterized by excellent insulation to maintain temperature and humidity levels, which is achieved by thick leaf layers and a supporting structure. As such, absence of food or low-quality winter nests as woodland hedgehogs enter hibernation could prove to be fatal. ("Invasive Species Compendium", 2010; Dunning, 2019; Johnson, 2015; Yarnell and Pettett, 2020)

However, what makes woodland hedgehogs particularly unique is their preference for urban and suburban habitats. It is not uncommon for Erinaceus species to be attracted to human-inhabited areas due to food and shelter availability derived from gardens, trash, farmlands, orchards, vineyards, and other man-made habitats. This preference for urban environments stems not only from abundant resources and alternative shelters, but also the absence of natural predators that either avoid such areas or are not as readily tolerated by humans. (Dziemian, et al., 2014; Hubert, et al., 2011; Johnson, 2015)

• Habitat Regions
• temperate
• terrestrial

• Terrestrial Biomes
• taiga
• savanna or grassland
• forest
• scrub forest
• mountains

• Other Habitat Features
• urban
• suburban
• agricultural

Systematic and Taxonomic History

Although many people believe hedgehogs are closely related to porcupines and other spiked mammals, woodland hedgehogs' closest relatives are actually within subfamily Galericinae (moonrats and gymnures), family Talpidae (moles and desmans), family Soricidae (shrews), and family Solenodontidae (solenodons). Although the woodland hedgehog genus itself was never known under a different name, E. roumanicus was formerly included in E. europaeus, then subsequently E. concolor, before morphological and genetic data suggested significant reason for differentiating E. roumanicus from all other species within Erinaceus. In addition, hedgehogs used to be called urchins due to their spiked appearance, but were also known as hedgepigs and furze-pigs before their modern-day name stuck. (Amori, et al., 2021; Ciszek and Myers, N.A.; Myers and Animal Diversity Web Staff, N.A.; New World Encyclopedia contributors, 2008; OneZoom Core Team, 2021; Wilson and Reeder, 2005)

• Synonyms

  • Urchin
  • Hedgepig
  • Furze-pig

• Synapomorphies

  • Modified hair (spines)
  • Ability to roll in protective "ball"
  • Resistance to snake venom and other environmental toxins
  • Plantigrade foot posture
  • Quadritubercular/bunodont upper molars
  • Trigonid/talonid basin lower molars
  • Dental formula: 2-3/3, 1/1, 3-4/2-4, 3/3 = 36-44
  • Complete zygomatic arch
  • Jugal present
  • Incomplete bullae
  • Relatively large incisors

Physical Description

Woodland hedgehogs have an ovular, medium-sized body. For example, E. europaeus individuals weigh between 600-1500g and have a total body length of about 15-30cm. Woodland hedgehogs' short, naked tails only contribute a few millimeters to their body length. With a weight range of 800-1200g, males tend to be heavier/larger than females, who have a range of 400-800g. It has been reported that woodland hedgehog size can be dependent on seasonality and resource availability, but size variation in this case is not remarkably significant. Contrarily, during the hibernation period, woodland hedgehogs gain and lose significant weight - up to 35% of their average weight - before and after entering hibernation. In addition, woodland hedgehogs have short legs with plantigrade feet. Each front paw is 5-toed with short, non-retractile, and recurved claws that are useful for digging and foraging. In contrast, the 4-toed hind paws are longer, narrower, and have constantly growing nails due to woodland hedgehogs’ burrowing behaviors. Together, these features allow woodland hedgehogs to exhibit excellent swimming and climbing skills. ("Invasive Species Compendium", 2010; Černá Bolfíková, et al., 2020; Ciszek and Myers, N.A.; Dunning, 2019; Pollock and Kanis, 2015)

Furthermore, woodland hedgehogs are often characterized by the coat of 5000-7000 protective keratin spines along their backs and crowns of their heads. Each spine is 0.75-1in in length and is rigid, hollow, and nonpoisonous. The spines are often brown, black, white, cream, or a mixture of these pigments in an agouti coloration scheme. When relaxed, the spines lay flat against the body. When threatened, woodland hedgehogs exhibit piloerection. Their spines jut out in all directions and the hedgehogs contract specialized dorsal muscles (the panniculus carnosus) to roll themselves into a protective ball. Hedgehog spines are also very efficient at wicking moisture and absorbing shock from falls or impacts to minimize injury. When born, hoglets are furless and only have about a hundred spines that are contained within a fluid membrane to protect the mother during birth, but these preliminary spines harden and grow alongside the thousands of adult spines they eventually obtain. Spines are gradually dropped and replaced throughout the woodland hedgehogs' lifetimes in a process known as quilling, but the overall coloration of the animal does not change. Meanwhile, the ventral side of woodland hedgehogs is covered with coarse brown, white, or cream colored fur. It is common to find a patch of white fur on the chests of E. concolor, and E. europaeus tends to be darker in appearance than the other species. However, all species' faces are furry with protruding black noses that exhibit an exceptional sense of smell. Their black eyes have rather poor sight, but their small, rounded ears allow for excellent hearing. Woodland hedgehog skulls are traditionally distinguished by their relatively large incisors, complete zygomatic arches, incomplete bullae, quadritubercular upper molars that are bunodont, and lower molars that are trigonids with talon basins. Other than weight, females and males are alike in morphology and appearance, and no polymorphisms have been reported in any Erinaceus species. ("Invasive Species Compendium", 2010; Černá Bolfíková, et al., 2020; Ciszek and Myers, N.A.; Dunning, 2019; New World Encyclopedia contributors, 2008; Pollock and Kanis, 2015)

• Other Physical Features
• endothermic
• bilateral symmetry

• Sexual Dimorphism
• sexes alike
• male larger

Reproduction

Woodland hedgehogs are solitary and only have extensive interactions when mating. Females can mate with more than 5 males in one breeding season while males try to mate with as many females as possible before entering hibernation. Males emerge 3-4 weeks earlier from hibernation than females to expand their home ranges and travel wider distances to find mates. Aggression between males during the breeding season has been observed, but because woodland hedgehogs are not territorial nor defend their mates, fights are low in frequency and resolve quickly. Females have multiple successive estrus cycles (they go into "heat") during the breeding season. When a male finds a potential mate, the female will hiss, grunt, and "pop" with her spines raised in defense while the male circles her. If the female is receptive to the male, she will eventually relax her spines and crouch closer to the ground, allowing the male to mount her and copulation occurs. If the female is not receptive, she will not allow the male to come near her and the male will eventually leave to find a more receptive mate. After mating, the female and male go their separate ways, likely on their way to find more mates. ("Invasive Species Compendium", 2010; Dziemian, et al., 2014; Pollock and Kanis, 2015; Roberts, N.A)

• Mating System
• polygynandrous (promiscuous)

Woodland hedgehogs' breeding season occurs sometime between April-September depending on the region, generally well before the subsequent hibernation season. Sexual maturity for males and females is reached by 9-11 months of age on average, although body weight is often a better indicator (i.e. females often become pregnant only after exceeding 700g). Males do not provide any parental investment to offspring. Before giving birth, females construct a breeding or reproductive nest, a long-term shelter that they will share with their offspring. Mothers care for and protect their offspring in this nest until the hoglets reach independence. Females can have up to two litters per breeding season with an average of 4-5 hoglets per litter, although it is rare for mothers to successfully raise more than 3 offspring to independence. In addition, second litters often have a lower survival rate due to having less time to develop and learn vital skills before the winter season. The gestation period of woodland hedgehogs is about 4-5 weeks; females do not undergo postpartum estrus. Hoglets are born blind with a weight range of 8-25g. Their eyes and ears open after 12-15 days, and after their deciduous teeth are lost around 4 months, their permanent teeth emerge around 7-9 weeks of age. The weaning period is about 5-6 weeks. At 3-5 weeks old, hoglets accompany their mother outside the breeding/reproductive nest to help forage before becoming completely independent around 4-6 weeks old, weighing 250g or more. Once independent, juveniles permanently leave the nest and venture alone. ("Invasive Species Compendium", 2010; Dziemian, et al., 2014; Johnson, 2015; New World Encyclopedia contributors, 2008; Pollock and Kanis, 2015)

An odd behavior that has been observed in woodland hedgehog mothers is spontaneous infanticide or desertion if the breeding nest is disturbed when the hoglets are newly birthed. Disturbances often include predator activity or other threatening circumstances. The reason for this behavior is unknown, especially because mothers will choose to relocate the breeding nest rather than commit infanticide or desertion if the hoglets are relatively older. (Johnson, 2015)

• Key Reproductive Features
• iteroparous
• seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual
• viviparous

Only females provide parental care to offspring, including before and after birth. After gaining enough weight (~700g) to ensure a healthy birthing process, females construct a long-term breeding or reproductive nest in which they will give birth to and care for their offspring. Hoglets are blind, deaf, small, and defenseless when born, so mothers provide food and protection for newly born hoglets until they are old enough (3-5 weeks) to accompany her on foraging expeditions outside the nest. At this point, hoglets will have opened their eyes and ears as well as started gaining their adult spines and teeth. During this time, hoglets learn vital food and nest foraging behaviors from their mother. Hoglets are fully weaned by 5-6 weeks and are usually independent thereafter. Once independent juveniles leave the nest, they do not return nor have any notable association with their mother. (Dziemian, et al., 2014; Pollock and Kanis, 2015)

• Parental Investment
• altricial
• female parental care
• pre-fertilization
  • provisioning
• pre-hatching/birth
  • provisioning
    • female
• pre-weaning/fledging
  • provisioning
    • female
  • protecting
    • female
• pre-independence
  • provisioning
    • female
  • protecting
    • female
• extended period of juvenile learning

Lifespan/Longevity

Wild woodland hedgehogs have an average lifespan of 3-5 years, though instances of individuals living up to 8 years have been recorded. In captivity, woodland hedgehogs can live up to 10 years. Woodland hedgehogs face the highest risk of mortality in their first few years of life. Juveniles are most vulnerable to deaths related to human activity, such as road killings, habitat fragmentation/loss, and accidental poisonings in their first year of life. Juveniles also face starvation and severe parasitism or disease at a higher rate than adults. Hibernation, which typically takes place sometime between September and May depending on the region, also proves to be a major obstacle to woodland hedgehog longevity. Hibernating woodland hedgehogs have a survival rate between 60-100%, although harsh or atypically warm winter conditions can lead to a death rate of up to 80%. This is due to a multitude of reasons, including but not limited to: insufficient body weight prior to hibernating, predation, inadequate hibernaculum conditions, parasites and infections, premature awakening due to warmer winters, and movement between nests throughout the hibernation period. Woodland hedgehogs' most prominent predator, badgers (Meles meles), have also contributed to recently declining E. erinaceus populations. This is not only due to badgers' predation of woodland hedgehogs, but also due to woodland hedgehogs' and badgers' shared prey types (insects) and habitats. For example, with an estimated 88% increase in badger populations across England and Wales, woodland hedgehogs are experiencing higher rates of starvation and habitat fragmentation induced by badger presence. ("Invasive Species Compendium", 2010; Dunning, 2019; Hof, et al., 2019; Johnson, 2015; Pollock and Kanis, 2015; Rasmussen, et al., 2019; Rautio, et al., 2016; Yarnell and Pettett, 2020)

Behavior

Woodland hedgehogs are solitary, highly motile mammals. As a result of the lack of interactions between individuals with the exception of the mating season, there are no social hierarchies in any woodland hedgehog species. They are terricolous and nocturnal animals that travel around 1-2 kilometers per night within their home ranges to forage for resources. They often stay within the same home range throughout their life if resources are consistently available. This means that woodland hedgehogs typically require a large and accessible area of suitable habitat, although they are not territorial. They will, however, become aggressive if they come across one another, huffing through their nose, squealing, lowering their head, and raising their spines in warning. This defensive position is the most common form of direct communication between woodland hedgehogs, though it is theorized that woodland hedgehogs rely heavily on olfactory cues to maintain a mutual system of avoidance within their overlapping home ranges. When it comes to woodland hedgehogs' predators such as owls (Bubo bubo) and badgers (Meles meles), woodland hedgehogs defend themselves by rolling into a ball, raising their protective spines, and huffing/squealing. However, more often than not, woodland hedgehogs choose to avoid areas in which predators are present altogether. This avoidance behavior has heavily contributed to habitat fragmentation, a concerning issue regarding woodland hedgehogs' conservation status.

Regardless of sex, woodland hedgehogs have been recorded to spend about 80% of their time foraging for food and nest materials during the middle hours of the night, returning to their nests for a period of time, then resume foraging until dawn. Males are known to move faster and cover more ground in their relatively larger home ranges than females, especially during the mating season. In the late summer, females tend to become more active and enlarge their home ranges after their young have been weaned.

Woodland hedgehogs build multiple types of nests. One type is a short-term day nest, of which the woodland hedgehogs use to rest and reside during the daytime outside of the hibernation period. They typically only use day nests for a few days at a time before moving onto a new one. Nests are built within thorny or dense vegetation, bramble, and nettles. Another type of nest is a breeding or reproductive nest. As the name suggests, breeding/reproductive nests are constructed for the purpose of protecting and raising hoglets until they are old enough to live on their own. The third type of nest is the hibernation nest, also known as a hibernaculum. Woodland hedgehogs construct many hibernacula because they tend to move up to four times between such nests during hibernation, and they can stay in these nests for up to 6 months as they hibernate. Males tend to enter and emerge from hibernation earlier than females to expand their home ranges and prepare for the successive breeding season.

An interesting behavior exhibited by woodland hedgehogs is a process called anointing, or anting. This behavior is carried out when a hedgehog comes across a new scent or taste. In response, the hedgehog will lick or bite the source material then proceed to lather a similarly scented, saliva-derived froth on their spines and flanks via licking. While not well-understood, researchers believe anointing is a way for hedgehogs to camouflage themselves scent-wise in the case that the new scent/taste proves to be dangerous. Others believe that anointing is another form of defense, in which predators have the potential to get poisoned or deterred by the froth if they come into contact with the hedgehog's spines.

Woodland hedgehogs are famous for living in close association and proximity with human populations, or within human-impacted landscapes such as farmlands, parks, and gardens. Humans are a great source of food, shelter, and predator protection for woodland hedgehogs. Many people build wood or cardboard houses for woodland hedgehogs to nest in as well as leave out food and water bowls. Woodland hedgehog enthusiasts even build protective corridors for the hedgehogs to safely pass through when traveling between gardens, across roads, through fencing, etc. (Bolfíková and Hulva, 2011; "Invasive Species Compendium", 2010; Dunning, 2019; Dziemian, et al., 2014; Johnson, 2015; New World Encyclopedia contributors, 2008; Pollock and Kanis, 2015; Rasmussen, et al., 2019; Rautio, et al., 2016; Wroot, 1984; Yarnell and Pettett, 2020)

• Key Behaviors
• terricolous
• nocturnal
• motile
• sedentary
• hibernation
• solitary

Communication and Perception

Although their vision is quite poor, woodland hedgehogs have exceptional senses of hearing and smelling. It is thought that olfactory sensing is the most common method of communication between individuals since overlapping home ranges are common. However, this communication is theorized to be a mutual agreement of avoidance rather than warning, as woodland hedgehogs are both non-territorial and solitary. Woodland hedgehogs mostly use their heightened hearing and smelling to seek out food, such as invertebrates, carrion, smaller reptiles, eggs, and more. As a nocturnal prey animal, good hearing and smelling is also useful for tracking and avoiding predators.

Woodland hedgehogs are somewhat vocal. When in major distress, they are known to exert a high-pitched squeal as they roll into a protective ball. When giving warning to a potential predator or another hedgehog, they huff and grunt in their defensive ball position, sometimes slightly lunging toward the threat to gain distance or weaponize their raised spines. (New World Encyclopedia contributors, 2008; Pollock and Kanis, 2015)

• Communication Channels
• visual
• tactile
• acoustic
• chemical

• Other Communication Modes
• pheromones
• scent marks

• Perception Channels
• visual
• tactile
• acoustic
• chemical

Food Habits

Woodland hedgehogs require about 90-150kcal worth of food per day to survive, depending on body size. Their slow metabolisms not only make them temperature-sensitive, but also sensitive to food availability. They are often characterized as insectivores because the bulk of their diet consists of terrestrial invertebrates such as beetles, caterpillars, earthworms, slugs, millipedes, and earwigs. Up to 160g of such invertebrates can be consumed by one woodland hedgehog per day. However, based on location and prey availability, woodland hedgehogs are also known as opportunistic and/or generalist predators. They have been reported to prey on the eggs of ground-nesting bird species, carrion, fungi, and small reptiles or amphibians. Older individuals tend to specialize on one prey type at a time, and they often exhibit prey switching on a seasonal basis. Before entering hibernation, woodland hedgehogs often need to attain a body weight of at least 450g, building up their fat reserves in order to have a higher chance of survival. For every day spent in hibernation, individuals can lose up to 0.2% of their body weight, so it is important for them to properly prepare.

One important aspect of woodland hedgehogs' diets is their anthropophilic behavior. Individuals who live close to human-inhabited regions tend to experience many advantages, one of which is high food availability. Many people leave out water and food bowls of meat-based pet food or mealworms for wild hedgehogs. Woodland hedgehogs also take advantage of farm crops, garden fruits/vegetables, and the invertebrates they find in such areas, like snails/slugs. Woodland hedgehogs are even known to scavenge through trash in backyards or parks. ("Invasive Species Compendium", 2010; Černá Bolfíková, et al., 2020; Dziemian, et al., 2014; Johnson, 2015; Rasmussen, et al., 2019; Rautio, et al., 2016; Wroot, 1984)

• Primary Diet
• carnivore
  • eats terrestrial vertebrates
  • eats eggs
  • insectivore
  • scavenger
• herbivore
  • frugivore
  • granivore
• omnivore

Predation

Woodland hedgehogs' main predators consist of large owls (Bubo bubo), badgers (Meles meles), and foxes (Vulpes vulpes). In urban areas, domestic dogs can also pose a threat to the hedgehogs. While adult woodland hedgehogs are typically protected from most predation events due to their spines, hoglets are more vulnerable and are often sought out by predators.

Woodland hedgehogs' primary anti-predator adaptations include their spines and their ability to roll into a protective ball while raising their spines in defense. Although woodland hedgehogs do not directly attack other individuals, they do "lunge" or "jump" at threats while in a ball in order to gain distance. They also give auditory warnings such as huffing, snorting, and hissing. An additional anti-predator mechanism includes the earth-toned agouti coloration of their spines that helps camouflage the woodland hedgehog in their environment. Finally, a common tactic exhibited by woodland hedgehogs is predator avoidance, especially in regards to badgers (Meles meles). In general, woodland hedgehogs will avoid areas in which predators are present. A common avoidance tactic for woodland hedgehogs includes staying close to urban areas, where predators such as badgers are not often found. ("Invasive Species Compendium", 2010; Hubert, et al., 2011; Pollock and Kanis, 2015)

• Anti-predator Adaptations
• cryptic

• Known Predators

  • European badger (Meles meles)
  • Eurasian eagle-owl (Bubo bubo)
  • Red fox (Vulpes vulpes)

Ecosystem Roles

Woodland hedgehogs' most important roles in an ecosystem are invertebrate population control (or pest control, in the context of urban habitation) and seed dispersal if such food types are available. Woodland hedgehogs have significant impacts on their prey populations in their local environment. Many researchers use hedgehog presence as an indication of habitat health: if hedgehogs are present, then there must be a healthy habitat which is often characterized by little to no fragmentation, varied habitat types, controlled predator populations, and a rich population of invertebrates. If they are not present and/or sparse in numbers, then there could be an unbalance in the ecosystem that should be investigated. It is important to note, however, that woodland hedgehogs' prey species could potentially suffer as a result of over-predation, especially if the prey population is already small or struggling to begin with. In addition, woodland hedgehogs are known vectors and/or hosts to a variety of parasitic species, which is often detrimental to their health and survival rates as well as individuals they come in contact with. ("Invasive Species Compendium", 2010; Dziemian, et al., 2014; Johnson, 2015; Pollock and Kanis, 2015; Rautio, et al., 2016)

• Ecosystem Impact
• disperses seeds

Economic Importance for Humans: Positive

Woodland hedgehogs are not the same hedgehog species that are now commonly kept as household pets (i.e. A. albiventris, H. auritus megalotis, H. collaris, and H. auritus). However, in urban environments, woodland hedgehogs are known as great pest-control contributors in gardens and even large-scaled farming fields. ("Invasive Species Compendium", 2010)

• Positive Impacts
• controls pest population

Economic Importance for Humans: Negative

Woodland hedgehogs are known carriers of many different parasitic species such as ticks and ringworm, as well as bacterial diseases such as salmonella. These infections and illnesses are capable of being transmitted to humans, other wildlife, and domesticated pets such as dogs and cats. In addition, woodland hedgehogs, although good pest control contributors, can also be seen as garden/farm crop pests, as they often eat fruits and vegetables alongside their invertebrate-dominated diet. (Pollock and Kanis, 2015)

• Negative Impacts
• injures humans
  • carries human disease
• crop pest
• causes or carries domestic animal disease

Conservation Status

Despite being listed as a species of least concern by the IUCN, one of the most prominent concerns regarding woodland hedgehog conservation is predator interactions, most notably when involving the European badger (Meles meles). With badger populations on the rise, woodland hedgehogs are experiencing habitat fragmentation due to predator-avoidance strategies. In other words, woodland hedgehogs tend to completely avoid areas where badgers and other predators are found. Seeing as woodland hedgehogs require relatively large home ranges and frequently travel while foraging, this fragmentation and/or loss of habitat - which is further amplified by infrastructure like roads, fencing, and paving - has proven detrimental. Consequences that arise with habitat fragmentation include limited prey populations, loss of shelters and nesting sites, road killings, killings by household pets like dogs, and accidental poisonings via insecticides or similar chemicals often found in urban areas and gardens. These issues are most common in the United Kingdom, where native woodland hedgehog populations have decreased by 30-50% since 2002. Nevertheless, all Erinaceus species around the world experience these issues in varying degrees, and so it is important for conservation strategies combating such issues to be employed.

To help conserve woodland hedgehogs' habitats, corridors have been constructed to connect habitat patches, and many people build box-like shelters on their properties for woodland hedgehogs to use for nesting. Additional legal protections have also been instated, such as adding woodland hedgehogs to the following lists and acts: Species of Principal Importance for Biodiversity, the Wildlife and Countryside Act of 1981, the Wild Mammals Protection Act of 1996, the Species of Principal Importance under Natural Environment and Rural Communities Act of 2006, the Biodiversity Action Plan (priority species), and more. A number of protected ranges have also been established for woodland hedgehogs, particularly for E. roumanicus and E. europaeus.

Another concerning issue is parasitism. Infestations of ticks like I. hexagonus and I. ricinus are commonly found in woodland hedgehogs. Such parasites can cause lethargy, hibernation disturbances or deaths, and viruses like tick-borne encephalitis. Woodland hedgehogs can also be infected via prey like earthworms, who have been found to transmit endoparasites in their infective stages. Infections and illnesses associated with ringworm (T. mentalgrophytes) and salmonella (S. enteriditis) are also common in woodland hedgehogs and can be transmitted interspecifically. Implications of wild hedgehogs spreading disease or infection to household pets and humans have been heavily considered, and many places advise people to keep their distance from wild woodland hedgehogs when possible. (Amori, et al., 2021; Černá Bolfíková, et al., 2020; Dunning, 2019; Dziemian, et al., 2014; Johnson, 2015; Pettett, et al., 2017; Pollock and Kanis, 2015; Rasmussen, et al., 2019; Rautio, et al., 2016)

• IUCN Red List [Link]

  Not Evaluated

Other Comments

The genus name Erinaceus derived from the Latin roots "ēris" or "ēr" (meaning: hedgehog) and "aceus" (meaning: resembling, having the nature of, belonging to). The oldest known ancestors of modern-day woodland hedgehogs were in genus Litolestes and genus Leipsanolestes. These ancestors existed during the Paleocene period (66-56 MYA), and from fossils discovered in Canada, Montana, and Wyoming, scientists discovered these ancestors were similarly sized to modern hedgehogs and were also insectivores. Other proposed ancestors include species from genera Oncocherus, Cedrocherus, and Deinogalerix, all of which vary in body and teeth size but generally share the same traits. More fossil analysis is required to confidently determine the ancestry of Erinaceus.

Hedgehogs have been a hot topic for many cultures and societies throughout time. They were seen as a symbol of rebirth for the ancient Egyptians due to their hibernation behaviors aligning with food availability. However, in Mongolia, there is a children's folklore story involving a hedgehog that is depicted as greedy and evil. There are many other negative associations connected to hedgehogs throughout history. In the Middle Ages, hedgehogs were a sign of bad luck if seen and/or found in your house, much like the superstition of black cats today. Additionally, it was believed that hedgehogs stole milk from cows and chicken eggs in the night. Shakespeare often used the word "hedgehog" as an insult in his works, and many Europeans in the Middle Ages believed that witches could shape-shift into hedgehogs, causing the English Parliament to establish a bounty on all discovered hedgehogs, dead or alive. Perhaps the reason why hedgehogs had so many negative associations is because of their sharp spines, nocturnal nature, and tendency to keep their eyes and head low/covered, which could be indicative of being secretive or untrustworthy.

An additional interesting fact about woodland hedgehogs is their immunity to snake and scorpion venom. Thus, if necessary, woodland hedgehogs can eat venomous snakes without consequence. Although not well-understood, researchers believe woodland hedgehogs have a neutralizing agent (a protein named erinacin) that combats venom's effects in the blood. (Omori-Satoh, et al., 2000; SWC Charity, N.A; WordSense Online Dictionary, N.A; Zinni, 2019)

Contributors

Sydney Collins (author), Colorado State University, Tanya Dewey (editor), University of Michigan-Ann Arbor.

References

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