The History of the European Fauna

by R. F. Scharff

As soon as the Miocene sea to the north of the mountains had retreated, a portion of the Alpine fauna poured into the plain, and many species have found their way to the British Islands, a few to Scandinavia and Russia. Westward too, the sea soon after retired and opened a way for those Alpine species which were vigorous enough to extend their range in that direction. South-eastward, of course, a highway had long ago been open, and Alpine forms which were able to migrate towards the incoming Oriental stream, had no difficulty in doing so. When they arrived in Greece, some turned westward again and populated Sicily, Southern Italy, Sardinia, Corsica, and Northern Africa, while others crossed over to Asia Minor, which was then connected with Greece, and wandered towards the Central Asiatic or the Himalayan Mountains.

But, as I remarked, few of the typical Alpine species reached Scandinavia and Lapland. I have already referred to the similarity between the Northern Scandinavian and the Alpine faunas in a previous chapter, and I have shown that this resemblance cannot altogether be explained by the supposition of an interchange in the faunas of the two regions. That this has taken place to some extent is probable, but the resemblance appears more especially due to the fact that the Alps and Scandinavia have been peopled from the same centres of distribution.

In order to make this matter quite clear, I will give a familiar example as an instance of the manner in which the present distribution can be explained without taking recourse to direct migration from the Alps to Scandinavia or vice versâ. The example I will take is that of a family of birds, not only of extreme interest from the fact of its northern range, but also from the pleasure it gives to those addicted to sport. This is the grouse family, the Tetraonidæ.

Let us commence with our British Grouse (Lagopus scoticus), which is peculiar to the British Islands. In Norway we find a Grouse (L. albus) which differs in habit, and in the fact of its turning white in winter; otherwise it is so closely allied to our Grouse that many ornithologists do not separate them specifically. No doubt the British Grouse is a descendant of this Scandinavian Willow-grouse. The latter is known also to inhabit Greenland and Arctic North America, and it is even found beyond Behring Straits in Northern Siberia. En route between Scandinavia and Asia, travelling in a westward direction, we meet with two other very local species of Grouse, which may be looked upon as offshoots of L. rupestris—viz., L. hyperboreus of Spitsbergen, and leucurus of Western North America. In Asia we then again find two kinds of Grouse, very closely related, and by some indeed regarded as belonging to the same species. These are L. rupestris and L. mutus. Mr. Ogilvie-Grant tells us of the former (p. 49), that it is merely a more northern rufous form of L. mutus, and that it goes through similar changes of plumage. In summer the males are readily distinguishable, but in winter it is impossible to tell one from the other. "L. rupestris taken as a whole," says Mr. Ogilvie-Grant, "appears to us barely specifically distinct from L. mutus." L. rupestris occurs not only in Northern Asia, but crosses the Behring Straits to Arctic America, being still found on the Aleutian Islands, which represent the last remains of the former land-bridge between Asia and North America, then eastward to Greenland and Iceland. However, while this form does not cross the confines of Asia in a westerly direction, its near relative L. mutus—better known as the Ptarmigan—does; and may perhaps have entered Europe as a Siberian and also as an Arctic migrant. It is still found in the Ural Mountains, in Finland, and the highlands of Scandinavia. It is gradually being driven out of the Alpine lowlands, while it has long ago disappeared from Germany, France, and Austria—in fact, from all the lowlands of Europe. It has also been met with in the Pyrenees and in some of the Spanish mountains. Similarly, the bird has become extinct in England and Ireland, while it is becoming more and more scarce in Scotland. The centre of distribution of the genus lies in Arctic America, and from there the genus has spread to Europe and Asia. L. albus and L. mutus appear in our continent chiefly as Arctic migrants.

The Black Grouse (Lyrurus tetrix) belongs to a closely allied genus, which has only two species. One of these is very local in distribution, being confined to the Caucasus, but the smallness of range is to some extent compensated for by the peculiarity of its name, which is L. mlokosiewiczi. The Black Grouse, on the contrary, is widely distributed. It inhabits Northern Asia from the Pacific to the Ural Mountains, and extends as far south as Pekin and the Tian Shan range. In Europe it is found from the extreme east to the Pyrenees, the Apennines on the south, and to Great Britain and Scandinavia in the north. It is important to note its absence from Spain, the Mediterranean islands, and Ireland; and we have learned that it is one of those Siberian migrants which have succeeded in establishing themselves in the Alps.

The Capercaillie (Tetrao urogallus)—another great favourite with sportsmen—is now generally separated generically from the Black Grouse, though they are of course near relations. Its range greatly resembles that of the Black Grouse, except that it does not go quite as far east in Siberia, not having been met with beyond Lake Baikal. From there it is found westward as far as the Pyrenees. It occurs also in the Carpathians and the Alps. In England, where it used to be known by the name Cock of the Wood, it became extinct at some remote period in history, while it lingered on in Scotland and Ireland until the end of the last century. In Scotland it has been reintroduced into several counties, and being protected, it appears to spread from these artificial centres of distribution.

Like the Black Cock, the Capercaillie is a Siberian migrant, and it is one of the few Siberian species which have reached Ireland, as I have had occasion to mention in dealing with the origin of the British fauna. Two other species of Capercaillie and an allied genus (Falcipennis) are met with in the extreme north-east of Siberia, and six other genera, all belonging to the grouse family, are confined to North America. We have therefore a very intimate relationship between the grouse of Asia and those of North America, some species even ranging right across the two continents.

The last genus of this very interesting family is Tetrastes. This grouse is not familiar to British ornithologists, since it is entirely absent from the British Islands. But sportsmen who have tramped over Scandinavia know it well by the name of Hazel Grouse. It is ashy grey in colour, barred and vermiculated with black. The Common Hazel Grouse (Tetrastes bonasia) is found from Northern Spain in the west right through the mountainous parts of Central and Northern Europe and Northern Asia to Kamtchatka and the Russian convict island of Saghalien in the Pacific. Besides the Common Hazel Grouse, two other species are known, one from Eastern Russia and the other from China.

Having now shortly reviewed the whole grouse family, we have seen that, although some species live within the Polar Circle, the majority are more or less confined to the more temperate or rather the less arctic parts of the Northern Hemisphere. They are quite absent from Southern Asia and even the southern parts of North America, and almost so from the Mediterranean basin. The whole range of the family is therefore suggestive of a northern origin, and this view agrees perfectly with all the details of distribution. The centre of distribution lies in Northern Asia, or in Arctic North America. From there the great genus Lagopus spread east and west, reaching Europe by these vastly divergent routes at a time when the physical geography was very different from what it is to-day. Several of the species common to the Alps and Scandinavia have migrated from Siberia direct to Eastern Europe. But we can now imagine how from a similar centre in Asia—perhaps at a rather more remote time—a species spread eastward across North America and Greenland to Scandinavia, and westward along the mountain ranges of the Tian Shan and the mountains of Asia Minor to Greece, and finally to the Alps. We should then have the same species in the Alps and in Scandinavia, not far removed from one another; but how different were their paths of migration! This, however, is not an imaginary instance. Such a migration must have actually taken place in a good number of instances among the terrestrial invertebrates and also among plants.

The view still current among many zoologists and botanists, that animals and plants were driven down into the plain from the mountains of Europe during the height of the Glacial period and there lived together till the return of a more genial temperature, when they retreated to their mountain homes, is a very plausible one. During their sojourn in the plain, the plants and animals—say from Scandinavia—intermingled with those from the Alps; and when the time of separation came, many Alpine forms retired northward with the Scandinavians, while many Scandinavians would go with the Alpines to their home. In this way the similarity between the Alpine and Scandinavian faunas and floras is assumed to have been brought about. These theories, first promulgated by Edward Forbes, were hailed with general satisfaction by the scientific world. Even Darwin says of them (p. 331), that grounded as they are on the perfectly well-ascertained occurrence of a former Glacial period, they seemed to him to explain in a satisfactory manner the present distribution of the Alpine and Arctic productions of Europe. To the present day this view meets with much favour among naturalists. It is somewhat similar to one which has recently been strongly supported by Professor Nehring and accepted by Professor Th. Studer and many others. They have never made it quite clear whether the pre-glacial fauna and flora are supposed to have been absolutely destroyed by the glacial climate, or whether part of them have been able to take refuge somewhere in the south; but the great mass of our Alpine plants and animals are believed to have been derived from the Siberian invasion, which I have fully described in the fifth chapter. This invasion spread over the European plain, and when the climate ameliorated, both animals and plants migrated north and south to the mountains. This view agrees with the earlier theory, except that the adaptation to Alpine conditions would, according to the former, have taken place since the close of the Glacial period, during which time no such modification or change of species seems to have been produced in other parts of the world. The characteristic fauna of the Alps, as has been gathered from the preceding pages, is mainly of Central Asiatic rather than of Siberian origin. Migration to the Alps took place by the Oriental route long before the Siberian invasion. Some of the species of the latter have penetrated to the Alps, but these Siberian species have not given to the fauna of the highest European mountain range the striking character with which we all associate it.