Clare Island Survey — Mammalia. 17 9 



If one may hazard a conjecture as to the cause of the misfortunes which 

 have overtaken the late pleistocene mammalia, it seems hardly possible 

 to escape from the conclusion that they found the Glacial Period an 

 insurmountable catastrophe. 1 The larger species — the Mammoth and the 

 Irish Deer — would starve first, their necessarily enormous supply of daily 

 food being cut off by the cold ; the Hyaena must needs succumb to the 

 same fate as its victims. The remainder of the fauna was probably driven 

 south. On the retirement of the ice the various species would naturally have 

 re-occupied their lost territory, but were faced by the competition of more 

 modern and more vigorous forms — the Arctic Fox by the Eed Fox; the 

 Eeindeer by the Eed Deer ; the Varying Hares by the Brown Hares ; the 

 Lemmings by numerous other smaller rodents. An additional factor in the 

 extermination of the Lemmings may have been the absence of the snow- 

 drifts, which must have been a great protection to them from carnivorous foes. 



The constituents of the Irish Mammal-fauna afford another argument in 

 favour of the extermination wrought by the Glacial Period, for it is in Ireland, 

 of all countries, that, the modern fauna being poor and competition not keen, 

 we should expect survivals from the Glacial Age. In Ireland, if anywhere, 

 should still be found the Lemmings, of which Dicrostonyx actually appears in 

 the upper strata of more than one cave ; the Bear should have lingered on at 

 least into historical times ; yet there is no trace of either. It seems impossible 

 to escape the conclusion that the whole Mammal-fauna perished, or was driven 

 south, and that there was no unglaciated land south of Ireland to which it 

 could retire, and from which it would issue to re-occupy Ireland. 



The case of the Wood Mice has already been fully discussed. It may 

 be as well to examine a little more closely, from an all-Ireland point of view, 



1 The possibility of mammals surviving the Glacial Period does not depend directly on climate or 

 even on a regular food-supply, but purely on the presence of vegetation. Vegetation implies an area 

 of snowless land exposed to sunshine during a summer, however brief ; it lies safe from frost under 

 the snows of winter. Small rodents, such as Lemmings, can exist wherever there is vegetation. 

 They do not even find it necessary to hibernate in winter, but burrow safely beneath the snow in 

 search of their food. Wherever the rodents are fairly numerous, a small carnivore, e.g., a Stoat or 

 Weasel, tan find a subsistence on them ; and if the vegetation be robust enough, another pair of linked 

 rodent and carnivore, hare and fox, becomes possible. They are still sheltered by the snow ; but being 

 unable to burrow for their food, the rodents must scratch for it in places where the snow is not too 

 thick — an essential condition ; and the carnivore obtains in summer a rich diet of berries and of birds 

 and their eggs. A further linked pair, in this case a ruminant and carnivore, is the Reindeer (or Musk 

 Ox) and the Wolf ; but the greater size of the ruminant now requires more specialized conditions 

 of vegetation. Cold water maintains a teeming population of fish and vertebrates, and marine carnivores 

 are possible as long as any open water (or access to it) exists, and a large terrestrial carnivore (Bear) to 

 prey on them, with, in summer also, a mixed diet of fish and vegetables, hibernating in winter 

 becomes at once possible. Thus far is easy and intelligible, and these conditions may be seen in 

 modern Greenland ; but the presence of an Elephant, requiring large quantities of food, would not be 

 possible under strict arctic conditions, and necessitates a forest or other source of ample food-supply ; 

 hut here again the laying on of much superfluous fat in summer would lessen the difficulties of winter. 

 K.I. A. PKOC. VOL. XXXI. J3 17 



