Identifications of hedgehogs (Erinaceus) in Europe

Introduction

Three species of Erinaceus occur in Europe: E. europaeus, E. roumanicus & E. concolor

The distinction of these three species is difficult and mostly not possible on photos, but in most cases, a species ID is possible based on their range.

Geographic Distribution

While the populations of E. europaeus ('western hedgehog') and E. roumanicus ('eastern hedgehog') are largely separated, there exists a contact zone in form of an area stretching from West-Poland through Czechia/West-Slovakia, Austria and along the Italian/Slovenian border towards the Istrian peninsula (Croatia). A second, large sympatric range is present in the Baltic region, extending eastwards into the European part of Russia. The easternmost distribution of E. europaeus is not too well known and might go as far as the Ural mountains. Also, the range of the species might be undergoing continuous shifting, especially E. europaeus extending its range in north-eastern Europe (more on this below).

E. concolor is an asiatic species, the nearest occurrences are in (the Asian part of) Turkey and the Caucasus.

Here are distribution maps of the three species (source: Wikipedia):

Source: [6]; blue: E.e. red: E.r orange: wild hybrids (in GER and CZ)

In European Russia, there is a broad area of overlap of the two species (Source: I. Zagorodniuk [2005]):

Morphological Differences

The color of the fur on the underside is usually lighter in E. roumanicus, and there are some typical head patterns of fur color mentioned, but as far as I understand it, there is a large variability in these features and morphological measurements or genetic analyses are often required to confirm a species ID. The potential of hybridisations is discussed later.
On average, E. europaeus is heavier and longer, while E. roumanicus has a longer tail [8].
Skeleton morphometrics are a much better way to distinguish the species, which is however mainly possible on dead animals (roadkill). E. europaeus has a larger skull and distinct shapes of the cranium and mandibles. But even here it is getting complicated, as in sympatry, those two species become morphologically more similar to each other - presumably by convergent selection [6]. I am not aware if this phenomenon applies to the fur coloration as well.

Sympatry and Hybridization

There has been little gene flow between the two species [7] and only few instances of hybridization have been reported in the contact zone of Central Europe, with the highest number in the city of Berlin [6]. The area of sympatry has remained relatively stable over time. A different picture can be seen in eastern Europe, where the two species only started to meet in a relatively recent time: According to a recent study [1], the range of E. europaeus extends eastwards until the Ural mountains, and in eastern Europe (Baltic region, Moscow area) there is a considerable proportion of ongoing hybridization among the population.

Here is the situation in Austria (E. europaeus above):