AlegsaOnline.com

Erinaceidae: the family of hedgehogs and gymnures

Erinaceidae is a small family of mammals that includes spiny hedgehogs and the hairier, scent-marking gymnures (moonrats); they belong to the order Eulipotyphla and have a long fossil history.

Author: Leandro Alegsa Creation date: November 13, 2022 Last updated: May 10, 2026

simple.wikipedia.org · CC BY-SA 3.0

Overview

Erinaceidae is a family of small to medium-sized mammals best known for the familiar hedgehogs and the less familiar gymnures or moonrats. Members of this family occur across Europe, Africa and much of Asia, and they are placed in the mammalian order Eulipotyphla, alongside shrews and moles. These animals play important roles as insectivores and opportunistic omnivores in many ecosystems.

Key characteristics

Erinaceids share a suite of traits that distinguish them from other small mammals. Typical features include:

Modified hairs or spines (in hedgehogs) used for defense; gymnures lack spines and resemble large, furry shrews.
Strong sense of smell and well-developed teeth for crushing invertebrates and small prey.
Nocturnal habits in many species; several temperate species hibernate or enter torpor.

Taxonomy and evolution

Erinaceids were once grouped in the broad, now-obsolete order Insectivora, but modern classifications place them in Eulipotyphla. The family is traditionally split into two subgroups: the spiny hedgehogs (often called Erinaceinae) and the gymnures or moonrats (Galericinae). Fossil evidence shows that this lineage has an ancient Cenozoic history, with early relatives known from Paleogene deposits.

Behavior, diet and ecology

Most erinaceids are opportunistic feeders that consume insects, worms, small vertebrates and plant material. Hedgehogs are famous for rolling into a tight ball when threatened; some species practice a curious self-anointing behavior in which they spread frothy saliva over their spines. Gymnures rely more on scent-marking and active foraging on the forest floor.

Human interactions and conservation

Hedgehogs appear widely in folklore and are sometimes kept as pets (notably certain African species), while gymnures are rarely encountered by people. Conservation status varies by species: habitat loss, road mortality and human persecution threaten some populations. For further reading on classification and species accounts see the family overview and specialist references such as hedgehog resources.

Notable distinctions

Although their spines and appearance may recall porcupines or rodents, erinaceids are not closely related to those groups. Their combination of dental, skeletal and behavioral traits separates them within Eulipotyphla and highlights their distinct ecological niche among small mammals.

Etymology

Old High German igil (9th century), Middle High German igel, Old Saxon igil, Middle Low German ēgel, Middle Dutch ēghel, Dutch egel, Old English igil, Old Norse īgull, is related as an l-derivation to Greek échis (ἕχις) 'snake', from Indo-European *eĝhi- 'snake'.

To the same Greek, or Indo-European source form belong with n-suffix Greek echinos (έχΐνος), 'hedgehog, sea-urchin' and with Indo-European įo-suffix: Serbian Church Slavonic ježь, Russian ёж, Lithuanian ežys 'hedgehog'.

All these derivations are to be understood as 'snake-animal, snake-eater', since the hedgehog eats snakes as well as insects, frogs, mice, etc.

Features

General physique

Hedgehogs are small to medium-sized animals. Their head-torso lengths vary from 10 to 45 centimetres. The hedgehog species with the largest and heaviest specimens is the greater rat hedgehog, weighing up to 2 kilograms. In contrast, specimens of the lesser rat hedgehog weigh 20 to 80 grams. The tail length of hedgehogs is variable, some representatives of the rat hedgehogs have a long tail, while it is usually only a short stub in the spiny hedgehogs.

The limbs of hedgehogs are relatively short and unspecialized. The thumbs or big toes are not opposable, as in all insectivores, and the feet end in mostly five toes with sharp claws - only the African hedgehogs have four toes on the hind feet. The tibia and fibula are fused in the lower half, as in many insectivores.

Hedgehogs are sole walkers. In rat hedgehogs, the hind legs are slightly longer than the front legs to allow rapid escape.

Coat

The fur of hedgehogs is mostly inconspicuous shades of brown or grey. The spiny hedgehogs have spines on their backs and flanks as an effective defensive weapon (in the case of the brown-breasted hedgehog, there are about six to eight thousand). These spines are modified hollow hairs. Each spine is equipped with an erector muscle (Musculus arrector pili). Spiny hedgehogs can curl up into a ball when threatened. The curling of the body is a complex interaction of numerous muscles, including the caudo-dorsalis muscle, which runs from the caudal vertebrae to the back and erects the spines, and a ring muscle (Musculus sphincter cuculli), which holds the sphere closed to conceal unprotected body parts. The abdomen, face and limbs are covered with fur in spiny urchins.

In contrast, rat hedgehogs have no spines and therefore (and due to the usually longer tail) give a rather shrew-like impression. Their grey-brown to black fur can be silky-soft or rough, depending on the species. The defense strategy of these animals is flight.

Head and teeth

The skull of hedgehogs is elongated and flat. A distinctive feature is the closed zygomatic arch and the independent zygomatic bone, which distinguishes these animals from most other insectivores. The head sits on a short neck. The elongated, movable snout is equipped with tactile hairs. The eyes and ears are relatively large compared to other insectivores. The sense of smell and hearing are probably the most important senses in the search for food, while visual perception plays only a subordinate role.

The skull is relatively small, accordingly, the brain is also simply built and small compared to the body mass. However, the olfactory bulb is well developed. The hedgehog also uses the Jacobson's organ.

The teeth of hedgehogs are provided with pointed cusps and sharp enamel ridges and are very well adapted to their carnivorous diet. All species have comparatively many teeth, and in some representatives the original number 44 of teeth of the Higher Mammals is preserved. The foremost incisor is often larger than the other incisors, and the upper molars have four cusps, the hindmost molar often being reduced.

Tooth formula		I	C	P	M
36–44	=	3	1	3–4	3
36–44	=	2–3	1	2–4	3

Digestive and reproductive tract

The digestive tract is very simply built. There is no appendix, the intestine is a simple tube and very short compared to the body length. In males, the testes are always located outside the abdominal cavity in scrotum-like folds of skin called cremasteric folds. The females have a two-horned uterus.