The History of the European Fauna

by R. F. Scharff

To judge by their distribution, the Bullfinches (Pyrrhula) are of Asiatic origin, for seven species out of ten are confined to that continent. Our common Bullfinch (P. europæa) probably came with the Oriental migrants, or perhaps its ancestors did. But the larger Northern or Russian Bullfinch (P. major) has no doubt entered our Continent directly from the east. We have in many groups similar instances of closely allied species or varieties, one of which, originating at a somewhat later stage than the other, took a different route of migration from that followed by its near relative.

The Pine-Grosbeak (Pinicola enucleator) is only known to British ornithologists as an exceedingly rare visitor. Its real home lies in the northern parts of Europe, Asia, and North America, and it is one of the most typical of the Siberian migrants.

But there are a number of other species of birds, which, though probably not of Siberian origin, only migrated westward recently, and have either not yet reached the British Islands, or which lead one to suppose, from their British range, that they are eastern forms.

Such, for instance, is the Nightingale (Daulias luscinia), which is probably of Oriental origin, but only visits England regularly in spring. There is no authenticated record of its ever having migrated either to Scotland or Ireland.

The Bearded Titmouse (Panurus biarmicus) is one of the eastern birds still resident in England, though unfortunately it seems to be on the verge of extinction. It is unknown in Scotland and Ireland. Another resident eastern species is the Nuthatch (Sitta cæsia), but neither of these is probably of Siberian origin.

The majority of the European Reptiles are probably of eastern origin. Among our British species, the Common Viper (Pelias berus), for example, is a typically eastern form. It is almost unknown in Southern Europe proper—that is to say, in Italy, the Balkan peninsula, and the Mediterranean Islands, but its range extends in the west as far as Spain, and in the east right across the Asiatic continent to Japan. It is well known that the Viper occurs in Scotland, and that neither it nor any other snake is found in Ireland. There is a legend, indeed, that snakes did once exist in Ireland and were banished from the island by St. Patrick, but unfortunately we have no historical evidence that such an interesting event actually took place. The Sand-Lizard (Lacerta agilis), another British species, may be looked upon as an eastern form. It is quite absent from Italy, the Balkan peninsula, and the Mediterranean Islands, but extends throughout Central Europe to the east.

Among the species of eastern Reptiles which have a mere local range in Europe might be mentioned the two Lizards, Phrynocephalus auritus and Agama sanguinolenta. They belong to the family Iguanidæ, which includes some very large species. Both of them are Asiatic forms, which have only just penetrated across the eastern steppes into Europe, where they inhabit the arid regions between the Caspian and the River Don in Southern Russia.

The species of Mammals living in Europe at the present day have, with few exceptions, migrated to our continent from other parts of the world. With regard to the Birds, it is possible that a somewhat larger number proportionally may be of European origin. Still, the great majority are, I think, to be regarded as immigrants. The autochthones are about equal to the immigrant reptiles, but many of the European Amphibians and the majority of the Fishes have probably originated on our continent. Some of the European Amphibia—especially among the tailless forms—appear to be immigrants from Asia. Thus the distribution of Rana arvalis in Europe is remarkably like that of a Siberian migrant. This frog occurs in Siberia, ranging southward as far as Persia and parts of Asia Minor. Crossing the European border, we find it in Russia, Upper Hungary, North and Central Germany,—being rarer in the south,—Denmark, and Scandinavia. According to Bedriaga, it crosses the Rhine only in Alsace, but occurs no farther west. It only just enters Holland. If we suppose the species to have originated in Central Europe, we should expect to find it in Switzerland, France, and perhaps England. If it had its ancestral home in Eastern Europe, we might expect it to occur on the Balkan peninsula. It seems to me more probable, therefore, that Rana arvalis came with the Siberian migration. This need not cause surprise, as the genus Rana is certainly not European. Out of about 110 species, only four are peculiar to Europe, the rest are scattered over all parts of the globe. Moreover, the fact that these four species are confined to Southern Europe would seem to indicate that the first species entered from the south, and there either became modified or spread over nearly the whole continent, as did, for instance, Rana esculenta and R. temporaria. Neither of these is by any means confined to Europe. R. esculenta ranges right across the Asiatic continent to Japan, and also enters North Africa, while the other has a wide distribution in northern and temperate Asia.

The various groups of Vertebrates are not dependent on each other in their migrations. Mammals and Birds extend their range with so much greater facility than Reptiles and Amphibians, that the surplus population of our neighbouring continents readily poured into Europe when—owing to changes of climate perhaps—they forsook their original homes.

We observe much the same differences of origin in the various groups of European Invertebrates. The Central European Molluscan fauna, remarks Dr. Kobelt, had already developed from the pliocene—in almost all its details, as regards formation of species and distribution—when the Ice-Age commenced (b, i. p. 162). Certain very interesting dislocations, however, in the range of land mollusca can be proved to have taken place about that time. Thus, as Dr. Kobelt has pointed out, the genus Zonites, which is now almost confined to the south-east of Europe, occurs in inter-glacial deposits in the valley of the Neckar, and even as far west as the Seine. If we might judge from this single instance, a molluscan migration from the east to the west seems to have occurred either in early or pre-glacial times. That Helix pomatia has migrated only comparatively recently from the East to Western Europe is rendered probable by its general range in northern and western Europe, but I cannot agree with Dr. Kobelt in the belief that Helix aspersa is of an equally recent origin in the North. No matter whether it has been found fossil or no, its range in the British Islands points to its having penetrated to Ireland when the latter was still connected with the Continent by way of England. Its migration from the Mediterranean dates therefore from early pleistocene or late pliocene times.