The History of the European Fauna

by R. F. Scharff

It seems evident then, according to these views, that with a comparatively slight change of the atmospheric conditions in the British Islands, we might have glaciers back again on all our highest mountain ranges in England, Scotland, and Ireland. But a widespread belief seems to prevail that the presence of glaciers implies a very low temperature. Snow and ice, however, are formed as soon as the temperature falls below freezing point; it does not matter whether there be 1 or 20 degrees of cold. Winters with a few degrees of frost will be just as favourable for the growth of glaciers as winters with the most severe cold.

Let us now see what the fauna and flora, as far as we know it, tell us of the climate of the Glacial period. At the very outset of our inquiry we are confronted with one very serious difficulty in the problem, and that is the supposed occurrence of inter-glacial mild phases alternating with colder ones during the Ice Age. At first, when traces of a temperate flora and fauna were discovered intercalated between two layers of boulder clay, their presence was explained by the supposition of a mild inter-glacial period. The famous Forest-bed on the east coast of England was also pronounced to be an inter-glacial deposit, though not coming precisely under this definition. In a few places one such bed was found, in some two or more, and in others none at all. Professor James Geikie discovered the evidences of no less than five of such inter-glacial epochs (p. 612) in Europe. Lest a reader of that author's remarkable work on the Ice Age might carry with him the idea that his hypotheses had met with general acceptance, a few quotations from almost equally high authorities on glacial matters will be useful. "That the glaciers," remarks Professor Bonney (p. 245), "were liable to important oscillations seems to be proved, but whether the evidence suffices to establish inter-glacial epochs, in the usual sense of the words, is more doubtful. When the snow-fields, as in the Alps, were much more extensive than they are at present, the glaciers which radiated from them would be more sensitive to minor climatal change. Even now they oscillate considerably. But during a Glacial epoch, an inch, either more or less, of precipitation might mean a considerable advance or retreat of the ice in the lowlands." French geologists look with even less favour on Professor Geikie's theories. Mr. Falsan (p. 212) says that he agrees with Messrs. Favre, de Saporta, Lory, de Mortillet, Desor, de Lapparent, Lortet, Chantre, Benoit, Fontannes, Depéret, and many other geologists, that there was only a single Glacial period, which, according to each particular region, might be divided into several phases, or into their equivalents—viz., one or more extensions of the ancient glaciers. But, on the whole, the view that there was at least one inter-glacial phase in the Glacial period meets with more general acceptance among geologists, I think, though the other opinion agrees much better with the nature of the fauna and flora as it has been revealed to us from the pleistocene deposits.

The occurrence of the remains of such arctic species of mammals as the Musk-Ox, Arctic Fox, Glutton, Lemming, and many others in these deposits, is frequently held up to us by geologists as a proof of the prevalence of an arctic climate while these beds were laid down. And indeed this appears at first a most satisfactory explanation of the phenomenon. But we must not judge the climate of Europe by their presence alone. As I shall explain more fully in Chapter V., these species invaded Europe owing to two circumstances. Firstly, because the climate of Siberia was becoming colder, necessitating a southward movement, with a consequent over-population in a reduced area; secondly, because a new short route to Europe had been opened up for them about the same time (see p. [221]). An invasion of Europe therefore took place from east to west. Similar invasions occur even at the present day, though not caused by a change in our climate, for every now and then immense flocks of the Siberian Sandgrouse emigrate to our continent. The mammalian migrants referred to are not to be looked upon as constituting the whole of our fauna at that time. Europe had a fauna of its own, and these invaders merely mingled with our animals. There was, no doubt, a keen struggle for existence, as the result of which the weaker in many cases succumbed. The hypothesis, however, that these Siberian migrants occupied an empty continent, forsaken by its pre-glacial inhabitants, is not supported by any facts.

All those who have investigated the pleistocene fauna have been struck by the extraordinary mixture of northern and southern types of animals. Professor Dawkins attempted to explain these facts by the supposition (p. 113) that "in the summer time the southern species would pass northwards, and in the winter time the northern would sway southwards, and thus occupy at different times of the year the same tract of ground, as is now the case with the elks and reindeer." "In some of the caverns," he continues (p. 114), "such as that of Kirkdale, the hyæna preyed upon the reindeer at one time of the year, and the hippopotamus at another."

A similar mingling of northern and southern faunas has also been observed in France. Mr. Falsan tells us (p. 236), that the remains of the mammals gathered and determined by Lartet and Gaudry belong partly to species which have been wrongly regarded as indications of a severe climate, and partly to such as are accustomed to a relatively mild temperature. In several localities in France, viz., at Levallois, St. Acheul, and Arcy, the remains of the Hippopotamus have occurred together with those of the Reindeer; whilst, according to Sir H. Howorth, the Lion has been found together with northern Voles at Bicêtre, near Paris. It is stated by the same authority (p. 115) that much the same conditions exist in Germany. "The lion and the spotted hyæna, the mammoth and rhinoceros, were found with the marmot, the suslik, the lemming, the pica, and the reindeer." At another locality near Thiede, remains of the Mammoth, woolly Rhinoceros, Horse, Ox, Reindeer, Arctic Fox, Lemming, and Pica are met with in the same deposit. In quoting the presence of these northern animals in Europe as evidence of an arctic climate, we commit a fatal mistake. Indeed, breeders of animals and those acquainted with zoological gardens know perfectly well that it is much easier to keep a northern species in a southern climate, than a southern species in a northern one. If in a Central European deposit occur a mixture of northern and southern forms of animals, the presence of the latter is more remarkable than that of the former. Logically, we should look upon the occurrence of southern species in the north, therefore, as supporting the view that a mild climate had induced them to travel northward. The only indication, indeed, of the presence of a Monkey in the British Isles in former times comes to us from the very same strata which have also yielded the remains of the Siberian mammals.

Before I conclude the consideration of the pleistocene fauna, it may be of interest to hear what Mr. Lydekker, one of our highest authorities on fossil mammals, has to say on this subject. "The most remarkable feature connected with this fauna is the apparently contradictory evidence which it affords as to the nature of the climate then prevalent. The Glutton, Reindeer, Arctic Fox, and Musk-Ox are strongly indicative of a more or less arctic climate; many of the Voles (Microtus), Picas (Lagomys), and Susliks (Spermophilus), together with the Saiga Antelope, appear to point equally strongly to the prevalence of a Steppe-like condition; while the Hippopotamus and Spotted Hyæna seem as much in favour of a sub-tropical state of things. Many attempts have been made to reconcile these apparently contradictory circumstances; one of the older views being that while the tropical types of animals lived during a warm interlude, they migrated southwards with the incoming of colder conditions to the arctic type of fauna. Since, however, it has now been ascertained that the remains of both tropical and arctic forms have been found lying side by side in the same bed, it is perfectly certain that such an explanation will not meet the exigencies of the case" (p. 300).

In Germany the remains of the Siberian mammals occur to a large extent in a pleistocene deposit known as "loess," and the theory has of late years gained ground that the latter is the fine dust-like sand accumulated during an intensely arctic dry climate. That many of the mammals discovered in the "loess" now inhabit the dry steppes of Eastern Europe and North-Western Asia seems to lend support to this supposition; but besides the mammals there are also land and freshwater shells in this deposit. The molluscan fauna certainly indicates no steppe-character, according to Dr. Kobelt (b, i. p. 166).

The attempt to utilise the Siberian migrants to Europe as indicators of a severe climate there, certainly fails to establish conviction. But it may be asked, surely the remains of the Alpine and Arctic plants which have been found in pleistocene deposits must decide this question in favour of one or the other hypothesis? Let us test it.

Plants being more directly affected than animals by changes of temperature and rainfall, remarks Mr. Clement Reid (p. 185), give evidence of the highest value when we inquire into former climatic conditions. The severity of the climate during the Glacial period is often assumed from the occurrence in pleistocene strata of such plants as Dryas octopetala, some species of willow, the dwarf birch, and others, which are now found in high latitudes and in the Alps, but are, as a rule, absent from the plain of Northern Europe. Professor J. Geikie goes so far as to state (p. 398) that it was unlikely that southern England during the climax of the glacial cold had much if any vegetation to boast of, and continues, "It is certain, however, that it was clothed and peopled by an Arctic flora and fauna when the climatic conditions were somewhat less severe, relics of that flora having been detected at Bovey Tracey." He believes, therefore, that an Arctic flora took possession of England as soon as the climate enabled it to live in the country. Arctic plants, according to this explanation of the sequence of events, were the first immigrants to reconquer the dreary, plantless wastes and make them habitable for mammals.