Class:Mammals
Order:Eulipotyphla
Family:Erinaceidae
The common hedgehog, or European hedgehog (Erinaceus europaeus Linnaeus, 1758), is a mammal belonging to the Erinaceidae family. It has archaic morphological characteristics (such as its dental formula and brain structure) that it shares with the first mammals that appeared on Earth at the end of the Cretaceous period.
There are numerous subspecies and it is widespread throughout most of Europe, including Ireland and Great Britain, where it was introduced. In Italy, the species is widespread with three subspecies (in addition to the nominal subspecies, also consolei and italicus) throughout the country, including Sicily and Sardinia.
The hedgehog measures up to 27 cm in length, with a weight that only in very rare cases exceeds one kilogram, and its tail usually reaches 2.5 cm in length.
It has an elongated skull and a small brain, which is mainly responsible for decoding olfactory signals, as smell is the hedgehog’s most developed sense. Its nose is large, black, and very mobile: the olfactory channels are constantly moistened by a mucous membrane. Their sight is less important to them, although they are still able to see up to 30 m away during the day and up to 12 m at night. Although their ears are small and half-hidden by fur, hedgehogs are able to hear frequencies between 250 and 60,000 Hz, well within the ultrasonic range, which helps the animal in its search for food. Their body is stocky and pear-shaped: in fact, their long, pointed snout contrasts with their short neck and rounded hindquarters. Their legs are short and stocky, but their feet are elongated and have five toes with pointed claws: the footprints left by their hind legs are very different from those left by their front legs, to the point that they can be mistaken by novices for the tracks of different species of animals.
Each specimen has up to 6,000 quills. Their color varies with the seasons: in the cold seasons, autumn and winter, the quills take on a darker brown color than in the warm seasons, when they are lighter in color. The fur also undergoes this change, taking on a lighter or darker color depending on the season. The quills are pointed and hollow, with lateral ridges, and each one is equipped with an innervated muscle that allows it to erect when the animal is excited or alert: each specimen has up to 6,000 quills.
In addition to protecting the animal from potential attackers, the quills also prevent serious damage from bumps or falls: each quill has a narrowing near the hair follicle that makes it flexible, allowing it to absorb even significant impacts. Although it appears to be a clumsy animal and generally moves slowly, the hedgehog is capable of running fast and is also an excellent swimmer.
During the day, it rests hidden in its burrow, usually consisting of a cavity in the ground located in the undergrowth, among tree trunks and fallen leaves. At night, it goes out in search of food, always following the same routes: it is not afraid to cross open spaces as it is well protected by its armour of spines. In fact, when a hedgehog encounters a possible danger, it reacts by immobilising itself and raising the spines on its back. Then, if the intruder touches it, it curls up into a ball. The attacker is thus faced with an impenetrable curtain of thorns. However, this tactic is ineffective against foxes, which urinate on the curled-up animal, forcing it to come out of its armor and then finish it off by biting its delicate snout.
Feeding
It is an omnivorous animal that enjoys various types of invertebrates, eggs and nestlings, reptiles, and amphibians; it does not even disdain eating small mammals, including mice. Hedgehogs are not afraid of the venomous bites of vipers, which they sometimes feed on, as the snake’s venomous teeth are shorter than their quills and rarely manage to penetrate the animal’s protective covering. Hedgehogs also eat acorns, berries, fruit, and other plant material without any problems, even feeding on leaves in extreme cases.
Cow’s milk is poisonous to hedgehogs: unable to digest lactose, it causes severe diarrhea, leading to the death of the animal.
Social behavior and relationships with humans
Hedgehogs are solitary creatures and generally tend to avoid contact with other hedgehogs. During the winter months, hedgehogs usually hibernate: however, this is quite risky for the animal, as if it has not accumulated sufficient body fat during the warmer months, it could die of starvation. During hibernation, the hedgehog’s body temperature drops from the usual 35°C to 10°C, while its heart rate drops from 190 to 20 beats per minute.
The average life expectancy is about 3 years, although they can reach 10 years of age in the absence of danger and especially if kept away from roads where they are too often killed by cars.
The gestation period of a female hedgehog can last from 30 to 50 days, and the number of young born can vary from 1 to 9. They are born with spines, but these are covered by a membrane to protect the mother during birth. After 36 hours, these first spines are replaced by a new coat that has developed inside, and a third coat will subsequently appear, definitively replacing the first two. At one and a half months old, the young resemble adults completely.
