Meet the hedgehogs
Insectivore mammals evolved during the Late Cretaceous and Early Palaeocene (roughly 60–70 million years ago). Many of these primitive insectivores are now extinct. The family Erinaceidae, which includes hedgehogs and appeared in Eurasia during the Eocene (54–38 Ma), has survived to the present day as an isolated group with no close relatives.
Somewhere around 26–38 million years ago, the family Erinaceidae split into two subfamilies. These were Erinaceinae (spiny hedgehogs); and Galericinae (hairy hedgehogs), the group containing the largest fossil hedgehog known to science, genus Deinogalerix, which was more of a carnivore than an insectivore and weighed approximately five kilograms.
Taxonomy and range
There are currently about 14 species of spiny hedgehogs in the world. They live in Europe and most of Asia, from where they spread to Africa over seven million years ago. Europe is home to three of these species: The European Hedgehog, Erinaceus europaeus, ranges from southern Iberia to southern Sweden, Norway and Finland, including the British Isles and the large islands of the western Mediterranean, except for the Balearic Islands; the Southern White-breasted Hedgehog, E. concolor , found in Eastern Europe, the Balkans, Greece and Turkey; and finally, the North African Hedgehog, Atelerix algirus, which lives mainly in non-desertic areas of Northern Africa and a narrow strip of the Iberian Mediterranean coast; in the Ebro depression, it is present in the provinces of Lleida and Tarragona. It can also be found in the Balearic and the Canary Islands. Africa is home to three other species in this genus: A. albiventris, A. frontalis and A. sclateri.
The European Hedgehog belongs to the nominal subspecies E. europaeus europaeus. The peninsular and Balearic hedgehog populations of the North African Hedgehog are considered to belong to A. algirus vagans, and the Canarian one to A. algirus caniculus. Nevertheless, certain authorities believe the mainland populations to belong to the nominal subspecies A. algirus algirus, the same one which is found in Northern Africa.
A very peculiar evolutionary trait of hedgehogs in the subfamily Erinaceinae is the transformation of part of their hair into stiff, sharp spines made of keratin, which are shed one by one every year and a half. Hedgehogs have also used them to develop the defensive system for which they are renowned. They make use of their peculiar muscle structure to roll up into a ball and become a sort of fortress. They make their escape once the danger is over. Nevertheless, the hedgehogs' protection is not impenetrable, since certain predators, such as Eurasian Eagle-owls (Bubo bubo), the European Badger (Meles meles) and some dogs, are able to find a way around it.
The zygomatic arch is broad and strong, enabling the insertion of powerful chewing muscles. Their dental formula is:
I 3/2 C 1/1 P 3/2 M 3/3
This dentition points towards an omnivorous diet, with teeth which are capable of crushing and slicing.
The average weight of eleven adult North African Hedgehogs (considering adults to be those over 500 g) was 618.45 g, while the average weight of eighteen females was 605.06 g. The maximum weights were 820 and 730 g, respectively. The average weight of forty-six adult European Hedgehogs was 770.5 g, while the average weight of forty-three females was 735.7 g. The maximum weights were 1.400 and 1.1 kg, respectively.
Biology and ecology
The European Hedgehog is a forest species with a certain degree of flexibility when it comes to choosing a habitat. Its optimum locations lie in transition areas between forests and other biotopes. This insectivore prefers moist places, such as deciduous forests, but can also live in Mediterranean Holly Oak forests and large gardens in suburban areas, including large parks in the centres of certain cities (e.g., the Barcelona Zoo gardens). It becomes rarer or disappears altogether with increasing aridity. Individuals living in dry areas take refuge near streams and torrents, provided they can find enough humidity there.
The North African Hedgehog, on the other hand, likes dry and sunny places. It is generally present in areas with less than 650 mm of annual precipitation. It is the only species found in the Balearic Islands, where it inhabits garrigues and other typically Mediterranean bush formations. On the mainland, it prefers farming areas or open spaces. The floodplains of the Parc Agrari del Baix Llobregat (Barcelona) are a typical biotope.
Use of space
The European Hedgehog is associated to river banks and shores. It seldom ventures deep into the forest and prefers not to stray away from the protection provided by plant cover. Its presence in areas next to urbanised places is explained by its tendency to live in ecotones and the lack of predators. A study conducted in the United Kingdom revealed that hedgehog density is inversely proportional to that of badgers (Meles meles).
The North African Hedgehog lives in areas with open and flat spaces. It is also associated to river banks, where it usually digs its den, but it prefers to feed in open spaces sometimes, right in the middle of farmed fields.
Hedgehogs are insectivores but tend to live on an omnivorous diet. They feed on all sorts of little animals, such as earthworms, snails, beetles, caterpillars and carrion. To a lesser extent, they also eat plant matter, including fruits.
Hedgehogs are nocturnal animals which become active about an hour after sunset. Apart from females which still have not weaned their pups, hedgehogs are never active during the day. Their activity pattern is bimodal, with a peak of activity during the early night and another one during the late night, just before they return to their dens. They usually spend the middle night hours resting.
Hedgehogs can enter a state of hibernation, the length of which varies depending on environmental conditions. Hibernation is preceded by a very active autumn period, during which they eat plentifully to build up their energy reserves. Nevertheless, hibernation is facultative, and they may choose not to hibernate if food is available all year round.
The breeding period, which is similar in both species, extends from April to August but can last until October. Any given female can breed twice over this period.
The courtship ritual is straightforward. Males approach the females and move around them while panting faintly. Females show their receptivity by flattening their spines and adopting a position which prevents a painful mating, with their rear limbs sprawled on the ground. The pregnancy period lasts five or six weeks.
Hedgehogs are protected by law all over the territory. It is illegal to kill them, capture them or keep them in captivity.
In general, the European Hedgehog does not seem to suffer from conservation issues, except in those places where traffic density, habitat loss and the treatment of plant cover have caused population declines.
The North African Hedgehog, on the other hand, is less common. On the coast, its habitats have been replaced with buildings and infrastructure, causing a high degree of population fragmentation. On the other hand, populations further inland (shires of Lleida) appear to have a better conservation status.
|Legislation and protection|
Cast. Erizo común
Cat. Eriçó fosc
Gall. Ourizo cacho
Esk. Triku arrunta
En. European Hedgehog
|Bern Convention Appendix III||
Decree 4/86 extending the list of protected species to Andalusia
Valencian Faunal Catalogue
Appendix II Protected
Catalan Animal Protection Act
Cast. Erizo moruno
Cat. Eriçó clar
Gall Ourizo lourido
Esk. Triku mairua
En. North African
|Bern Convention Appendix II
Habitats Directive Annex IV
|National Catalogue of Endangered Species
Of special interest (except for the Canarian population)
Andalusian Catalogue of Endangered Species
Catalan Animal Protection Act
The role of the Hedgehog Project
Improving our knowledge of hedgehog distribution
The data collected within the project will be used to determine the range and population status of the two hedgehog species found in the studied area. So far, and with the data collected during 2008 (which also include previous years' encounters), a first state of matters has been established with potential range maps which will improve as new data become available. These will be used in the future to detect changes in distribution.
The maps generated by modelling must be seen as potential range maps, since they represent the probability of encounters depending on the suitability of natural environments and climate conditions. With time, and thanks to everyone's efforts, we will gradually tweak them until they become actual distribution maps, an indispensable tool if we are to manage species properly.