224 



KNOWLEDGE 



[Oct. 12, 1883. 



A NATURALIST'S YEAR. 



TUE SHREWS DIE. 

 By Grant Allen. 



ON every country footpath in October, if only you care 

 to look for them, you will find here and there, at 

 long intervals, the soft furry dead bodies of the pretty 

 little, unobtrusive, English shrew-mice. So commonly arc 

 they to be noticed in such situations, indeed, that the 

 country people have (or had) an ancient superstitious 

 belief to account for the fact ; they held that a shrevr 

 couldn't run across a public path without immediately and 

 incontinently dying. Doubtless the notion was closely 

 connected with that general idea of the uncaniiiness of the 

 shrew, which is bound up with the incantations of shrew- 

 ashes and shrew-murraiu ; as a witch-animal, it couldn't 

 show itself on the open, away from the secresy of night, 

 and darkness, and forest shades, without paying the penalty 

 of extinction to the light of day and the broad sunshine : 

 for shrews, like bats, moles, frogs, and lizards, are held as 

 small deer of ill-omen in old-fashioned folk-lore, doubtless 

 because of their retiring habits, and their indirect connec- 

 tion with graveyards, stone monuments, barrows, mounds, 

 and other recognised haunts of ghosts or fairies. To the 

 sober eye of unimaginative science, however, the number of 

 shrews found dead on roads or highways in autumn is 

 merely an index of the far greater numbers which must be 

 scattered about unobserved among the grass of meadows 

 and the tangled undergrowth of the hedgerows, where 

 especially they love to lurk in little shrinking, domestic 

 colonies. So far as one can judge, the shrew tribe is one 

 of those on which the Malthusian problem is always press- 

 ing with annual persistence. Like the natives of India, 

 the shrews, in their crass ignorance of political economy, go 

 on increasing with careless improvidence during all seasons 

 when the food supply is abundant, and then get summarily 

 checked again by a vast famine system the moment it 

 begins to fail or diniinish. Every spring each female 

 shrew brings forth a litter of six or seven young, and as 

 these are but little checked by natural enemies, owing to 

 their small size and extreme timidity, they find plenty of 

 food throughout the summer, when beetles, worms, slugs, 

 and petty snails abound everywhere among the fields and 

 thickets. But when autumn comes the food-supply falls 

 short, and then the shrews have to be thinned out piti- 

 lessly by the inexorable law of nutural selection. Enough, 

 of course, survive to continue the existence of the species 

 undiminished ; and as long as that is the case Nature is 

 perfectly satisfied : " So careful of the type she seems, so 

 careless of the single life." 



The type, indeed, is one which naturalists at least would 

 not willingly see perish. Like as the shrews are in external 

 appearance to the smaller rodents — so much so that it is a 

 mere bit of purist scientific afl'ectation to speak of them 

 otherwise than as shrew-mice — they are really insectivores 

 of the purest water, and in no way truly related to the rats 

 and mice. Their close outer similarity depends entirely 

 upon adaptive resemblance ; it is one more instance of the 

 common law that plants or animals of very similar habits ac- 

 quire very similar external shapes, however great their real 

 underlying difff rences of descent. In other words, the same 

 circumstances which have modified the central rodent form 

 into the little harvest mice and field voles have also modified 

 the central insectivorousform into theshrews and their allies. 

 Now, the great evolutionary interest of the shrews consists 

 in the fact that they are themselves in many ways the most 

 primitive and unspecialised insectivores at present existing. 

 Taking the small insectivorous group as a whole, it is 



remarkable for the extreme divergence and high specialisa- 

 tion of most of its members : though the entire number of 

 living insectivores is but very few, they yet have to be 

 divided into some ten or twelve distinct families, some of 

 which are marked off from the others by highly developed 

 external modifications. For example, we have within this 

 single group such unlike animals as the hedgehog, with his 

 spiny coat and his habit of rolling himself up into a closely- 

 bristling ball ; the underground mole, with his small half- 

 buried eyes, his thick coat of peculiar fur, his strong 

 digging paws, and his long pointed muzzle ; the squirrel- 

 like bangsrings of the Malay Archipelago, with their big 

 bushy tails, their arboreal habits, and their active, rest- 

 less disposition ; the pretty little jumping elephant- 

 shrews of South Africa, like kangaroos in miniature, 

 semi-erect on their tall hind legs, and possessed of 

 extremely thin proboscis-like muzzles ; and, finally, 

 strangest of all, the big, floundering colugo or galeo- 

 pithecus — the " flying lemur " of early biologists — with its 

 wide parachute membrane between the limbs and body, 

 and its bat-like trick of gliding lightly through the air from 

 one tree or branch to another. This extraordinary variety 

 of external form within the limits of a single small group 

 like that of the insectivores, almost irresistibly suggests the 

 idea that we have here the last feeble remnants of a once 

 wide-spread and important mammalian order. The great 

 mass of the connecting links have apparently died out, and 

 have left the few existing genera of insectivores either as 

 nocturnal, or subterranean, or aquatic creatures in the 

 great continents, or else as solitary denizens of outlying 

 insular or peninsular regions. 



A rapid glance at the present distribution of the prin- 

 cipal modern insectivores will show this probability far 

 more clearly than any amovmt of mere reasoning would do. 

 The colugo, for example, lingers on in the Malay Peninsula, 

 Sumatra, and Borneo, — just the sort of places in which 

 stray members of decadent groups are always found. The 

 bangsrings and their allies are also almost peculiar to the 

 Malayan region. The elephant shrews belong chiefly to 

 South Africa, long a separate insular district, as Mr. 

 ^\"allace has shown, with a very antiquated local fauna of 

 its own. The hedgehogs, though far more cosmopolitan in 

 their distribution (so far as the old world is concerned) are yet 

 marked as outlying members of a dying family by a large 

 combination of features — they have survived by virtue of 

 their prickly defences, their nocturnal habits, their prowl- 

 ing life, and their burrowing instinct ; and one very primi- 

 tive form of hedgehog — which is, in fact, almost shrew-like 

 in most of its peculiarities, and possesses only the merest 

 rudiments of spines — is confined to the very isolated 

 IMalayan region, where it has loitered in the early shape 

 without any modification ; while its more hardly-pressed 

 neighbours in the great continents have all been weeded 

 out, unless possessed of very spiny prickles, till now 

 they have assumed the familiar form of the common 

 English hedgehog. Another closely - related family, 

 that of the tanrecs, is all but wholly confined to 

 Madagascar, that fertile nurse of ancient types, elsewhere 

 superseded ; the only exceptions are those of two similar 

 little animals — the solenodons, one of which inhabits 

 Haiti, while the other is found nowhere but in the tropical 

 jungles of Cuba. It is a very significant fact that allies of 

 this ancient Mascarene family should turn up thus unex- 

 pectedly in the AYest India Islands. Whenever we find 

 closely allied .species thus isolated in two remote and 

 peculiar habitats, with no other of their congeners inter- 

 vening, we may reasonably conclude that the group to 

 which they belong was once far more widely dispersed over 

 the globe, but that they have gradually been superseded in 



