recently shown in the case of the greater and lesser horseshoe bats
(Rhinolophus ferrum-equinum and R. hipposiderus), that during
the early period of their occupation of the winter retreat, hibernation,
in the strict sense of the word, does not take place, and that
even later in the season the sleep is constantly interrupted,
especially when the temperature of the air rises above 46° F.,
and that during their wakeful intervals they crawl about and feed
apparently upon the insects which live throughout the year in the
caves. This is also true of the long-eared bat (Plecotus auritus),
and probably of other species of this group. At Mussoorie in the
Himalayas, and in other parts of northern India, insectivorous
bats, such as Rhinolophus luctus and Rh. affinis, pass the winter
in a semi-torpid state, and are rarely seen abroad during the cold
season. The fruit-eating bats, on the contrary (Pteropidae),
which are more southern in their distribution and are restricted
in the Himalayas to the warmer valleys and lower slopes of the
mountains, are as active in the winter as at other times of the
year (Blanford).
Although almost as exclusively insectivorous as bats, moles and shrews do not, so far as is known, hibernate. This distinction between two groups so nearly alike in diet, no doubt depends upon the difference in their habitats and in those of the creatures they live upon. By tunnelling deeper in winter than in summer, moles are still able to find worms and various insects buried in the earth beyond the reach of frost; and shrews hunt out spiders, centipedes and insects which in their larval, pupal or sexual stages have taken shelter and lie dormant in holes and crannies of the soil, beneath the leaves of ground plants or under stones and logs of wood. In view of the perennially active life of the two insectivora just mentioned, it is a singular fact that the common hedgehog (Erinaceus europaeus)—the only member of this order besides genera referable to the moles (Talpidae) and shrews (Soricidae) that inhabits temperate and north-temperate latitudes in Europe and Asia—passes the winter in a state of torpor unsurpassed in profundity by that of any species of mammal so far as is known. Possibly the explanation of this seeming anomaly may be found in the bionomial differences between the three animals. The subterranean feeding habits of the mole render hibernation unnecessary on his part. Therefore the shrew and the hedgehog, both surface feeders for the most part, need only be considered in this connexion. As compared with shrews, amongst the smallest of palaearctic mammals, the hedgehog is of considerable size. Moreover, in point of vivacious energy it would be difficult to find two mammals of the same order more utterly unlike. Hence in winter when insects are scarce and demand active and diligent search, it is quite intelligible that the shrews, in virtue of their smallness and rapidity of movement, are able to procure sufficient food for their needs; whereas the hedgehogs, requiring a far larger quantity and handicapped by lack of activity, would probably starve under the same conditions. Like the common hedgehog of Europe, the long-eared hedgehog (Erinaceus megalotis) hibernates in Afghanistan from November till February. The tenrec (Centetes ecaudatus), a large insectivore from Madagascar, aestivates during the hottest weeks of the year; and specimens exhibited in the Zoological Gardens in London preserved the habit although kept at a uniform temperature and regularly supplied with food.
Amongst the Rodentia, no members of the Lagomorpha (hares, rabbits and picas) are known to hibernate, although some of the species, like the mountain hare (Lepus timidus), extend far to the north in the palaearctic region, and the picas (Ochotona) live at high altitudes in the Himalayas and Central Asia, where the cold of winter is excessive, and where the snow lies deep for many months. It is probable that the picas live in fissures and burrows beneath the snow, and feed on stores of food accumulated during the summer and autumn. The Hystrico-morpha also are non-hibernators. It is true that the common porcupine (Hystrix cristata) of south Europe and north Africa is alleged to hibernate; the statement cannot, however, be accepted without confirmation, because the cold is seldom excessive in the countries it frequents, and specimens exhibited in the Zoological Gardens in London remain active throughout the year, although kept in enclosures without artificial heat of any kind. Even the most northerly representative of this group, the Canadian porcupine (Erethizon dorsatus), which inhabits forest-covered tracts in the United States and Canada, may be trapped and shot in the winter. Some members of this group, like capybaras (Hydrochaerus capybara) and coypus (Myocastors coypus) which live in tropical America, are unaffected by the winter cold of temperate countries, and live in the open all the year round in parks and zoological gardens in England. Several of the genera of Myomorpha contain species inhabiting the northern hemisphere, which habitually hibernate. The three European genera of dormice (Myoxidae), namely Muscardinus, Eliomys and Glis, sleep soundly practically throughout the winter; and examples of the South African genus Graphiurus practise the same habit when imported to Europe. If a warm spell in the winter rouses dormice from their slumbers, they feed upon nuts or other food accumulated during the autumn, but do not as a rule leave the nests constructed for shelter during the winter. According to the weather, the sleep lasts from about five to seven months. In the family Muridae, the true mice and rats (Murinae) and the voles and lemmings (Arvicolinae) seem to remain active through the winter, although some species, like the lemmings, range far to the north in Europe and Asia; but the white-footed mice (Hesperomys) of North America, belonging to the Cricetinae, spend the winter sleeping in underground burrows, where food is laid up for consumption in the early spring. The Canadian jumping mouse (Zapus hudsonianus), one of the Jaculidae, also hibernates, although the sleep is frequently interrupted by milder days. Some of the most northerly species of jerboas (Jaculidae), namely Alactaga decumana of the Kirghiz Steppes and A. indica of Afghanistan, sleep from September or October till April; and the Egyptian species (Jaculus jaculus) and the Cape jumping hare (Pedetes caffer), one of the Hystrico-morpha, remain in their burrows during the wet season in a state analogous to winter sleep. The sub-order Sciuromorpha also contains many hibernating species. None of the true squirrels, however, appear to sleep throughout the winter. Even the red squirrel (Sciurus hudsonianus) of North America retains its activity in spite of the sub-arctic conditions that prevail. The same is true of its European ally Sc. vulgaris. The North American grey squirrel (Sc. cinereus), although more southerly in its distribution than the red squirrel of that country, hibernates partially. Specimens running wild in the Zoological Gardens in London disappear for a day or two when the cold is exceptionally keen, but for the most part they may be seen abroad throughout the season. On the other hand, ground squirrels like the chipmunks (Tamias) and the susliks or gophers (Spermophilus) of North America and Central Asia, at all events in the more northern districts of their range, sleep from the late autumn till the spring in their subterranean burrows, where they accumulate food for use in early spring and for spells of warmer weather in the winter which may rouse them from their slumbers. The North American flying squirrel (Sciuropterus volucella) and its ally Pteromys inornatus are believed to hibernate in hollow trees. All the true marmots (Arctomys), a genus of which the species live at tolerably high altitudes in Central Europe, Asia and North America, appear to spend the winter in uninterrupted slumber buried deep in their burrows. They apparently lay up no store of food, but accumulate a quantity of fat as the summer and autumn advance, and frequently, as in the case of the woodchuck (A. monax) of the Adirondacks, retire to winter quarters in the autumn long before the onset of the winter cold. The prairie marmots or prairie dogs (Cynomys ludovicianus) of North America, which live in the plains, do not hibernate to the same extent as the true marmots, although they appear to remain in their burrows during the coldest portions of the winter. Beavers (Castor), although formerly at all events extending in North America from the tropic of Cancer up to the Arctic circle, do not hibernate. When the ground
