The Snakes of Europe

by George Albert Boulenger

Hydrophiinæ.—Indian and Pacific Oceans.

Elapinæ.—S. Asia, Africa (exclusive of Madagascar), Australia and Tasmania, Fiji Islands, C. America (extending into the S. parts of N. America), S. America.

Amblycephalidæ.—S.E. Asia, C. and S. America.

Viperinæ.—Europe, Asia, Africa (exclusive of Madagascar).

Crotalinæ.—S.E. Europe, Asia, America.

The Zoogeographical Regions into which the world is usually divided (Palæarctic or Europo-Asiatic, Oriental or Indian, Ethiopian or African, Australian, Nearctic or North American, Neotropical or South American) do not lend themselves any better than the ordinary divisions of physical geography to the study of the distribution of Snakes. Contrary to what we find in dealing with the Tortoises, Australia does not show any special affinity to South America, and, as in the case of the Lizards, it must be regarded as an impoverished extension of the Indo-Malay fauna; as with the Lizards, also, Europe and Africa hang together, whilst Madagascar stands apart, distinguished by many negative features and some points of agreement with South America (Boidæ). There is a greater difference between the Snakes of Europe and those of Eastern Asia than there is between the latter and those of North America, whilst in Lizards a primary distinction must be made between the Old World and the New. Southern Asia east of Persia (the Oriental Region) is the great Ophidian centre, all the groups mentioned above, with the exception of the Dasypeltinæ, having representatives within its limits, and a large and very distinct family, the Uropeltidæ, being confined to it. The Pythoninæ occur along with the Boinæ, the Viperinæ with the Crotalinæ, and the Elapinæ are represented by varied forms, as they are also in Africa and still more in Australia, where they form the overwhelming majority, and in some parts, as well as in Tasmania, the exclusive Ophidian population. The coasts of India and Malaya are also the home of the great majority of the Hydrophiinæ. Large genera like Tropidonotus, Zamenis, and Coluber, extend over the Europo-Asiatic and North American regions, but they are equally well represented in the Oriental. The great difference between Madagascar and Africa is, as we have said, very striking. Madagascar possesses Boidæ generically identical with those of South America, but otherwise only Typhlopidæ, Colubrinæ, and Dipsadomorphinæ; whilst in the greater part of Africa the Boinæ are replaced by the Pythoninæ, and the Glauconiidæ, Elapinæ, and Viperinæ are generally distributed. North America agrees with Asia and South America in its Crotalinæ, otherwise its Ophidian fauna is not very different from that of Europe, although much richer, and South America shares the Glauconiidæ with Africa and the Ilysiidæ with Southern Asia. South America is rich in Colubrinæ and Dipsadomorphinæ, nearly all generically different from those of other parts of the world, and the Elapinæ are represented by the single genus Elaps, with many species, two of which extend to the southern parts of North America.

This rapid sketch of the principal facts of Ophidian distribution suffices to show how difficult it would be to frame geographical regions that would give expression to these facts. Such regions would necessarily be very different from those adopted in dealing with the distribution of the other divisions of the class Reptilia. This is a task which need not be attempted on the present occasion.

A few words as to the salient characters of the European fauna, which is a poor one as compared with other parts of the world. The single species of the genera Typhlops and Eryx must be regarded as outposts from South-Western Asia; the single species of Ancistrodon, which extends from Central Asia into a very small territory to the south-east, is also an Asiatic type. The genera Tropidonotus, Zamenis, Coluber, Coronella, and Contia, are characteristic of the Northern Hemisphere, and the first three are, besides, equally well represented in the Oriental region; a few species of Tropidonotus are also found in Africa and Madagascar. Cœlopeltis, Macroprotodon, and Tarbophis are the northern outposts of an Afro-Indian group, although, with the exception of the third, exclusively confined to the circum-Mediterranean district. The genus Vipera is also represented in East Africa and in Southern Asia, but the species V. berus is essentially a northern type, extending to the highest latitude reached by any snake, and ranging all over Northern Asia to the Amur and Sachalien. The same species reaches the greatest altitude at which any snake has been observed on the northern side of the Alps—viz., 9,000 feet.

Of the twenty-eight species inhabiting Europe, only two are generally distributed: Tropidonotus natrix and Coronella austriaca. One is to be regarded as a northern form, although occurring locally in the south: Vipera berus. It is the reverse with Coluber longissimus. The others may be described as southern forms, two only as ranging from west to east: Zamenis gemonensis and Cœlopeltis monspessulana; one of more central habitat: Vipera ursinii. The remainder may be divided into two groups—those of more western, and those of more eastern distribution. To the first group belong Tropidonotus viperinus, Zamenis hippocrepis, Coluber scalaris, Coronella girondica, Macroprotodon cucullatus, Vipera aspis and Vipera latastii; to the second, Typhlops vermicularis, Eryx jaculus, Tropidonotus tessellatus, Zamenis dahlii, Coluber quatuorlineatus, dione, leopardinus, Contia modesta, Tarbophis fallax and iberus, Vipera renardi, ammodytes, lebetina, and Ancistrodon halys.

A remarkable fact in the distribution of European Snakes is the altitudinal range of Vipera berus, V. aspis, and V. ursinii. The first being the northernmost snake, generally distributed in Northern Europe and more locally in the south, should, one would expect, be a mountain form in the south. This is so in Switzerland, where it occurs chiefly between 2,500 and 9,000 feet, on the northern aspect of the Alps, whilst V. aspis lives at altitudes below 5,000 feet; but on the southern aspect of the same chain things are reversed, and V. berus is replaced by V. aspis, which reaches an altitude of 9,700 feet, whilst the former shows a tendency to abandon the mountains, and has established itself in a few localities in the plain of North Italy. Again, in France V. berus is the northern and V. aspis the southern species, yet the latter is the only one found on the French side of the Pyrenees (up to 7,250 feet), whilst the former reappears in North-Western Spain and Portugal at very low altitudes, even at sea-level. V. ursinii is a mountain form in Italy (Abruzzi), in France (Basses-Alpes), and in the Balkan Peninsula (up to 6,800 feet); but it is restricted to the plain in Lower Austria and Hungary, where V. berus occurs only in the mountains.