The Harvest Mouse

Discovery & Context

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Introduction

1 Discovery and Context

2 Micromys - Description

3 That Wonderful Procreant Cradle

4 Where Are They Now?

5 Deaths and Entrances

6 Keeping Harvest Mice as Pets

Appendix A

Slowly, silently, now the moon
Walks the night in her silver shoon;
This way, and that, she peers, and sees
Silver fruit upon silver trees;
One by one the casements catch
Her beams beneath the silvery thatch;
Couched in his kennel, like a log,
With paws of silver sleeps the dog;
From their shadowy cote the white breasts peep
Of doves in silver feathered sleep
A harvest mouse goes scampering by,
With silver claws, and silver eye;
And moveless fish in the water gleam,
By silver reeds in a silver stream.

Silver by Walter De La Mare

Discovery.
Mammals.
Rodents.
British Rodents.
British Mice.
Gilbert White and the Harvest Mouse.

Discovery of the Harvest Mouse

At almost exactly the same time that Gilbert White was putting together his observations on the “non-descript” mouse, a seriously keen German-born naturalist was, at the bequest of Czarina Catherine II, undertaking a six-year expedition through Russia and Mongolia that took him into the Volga region where he independently discovered the Harvest Mouse. Peter Simon Pallas is well known to bird-watchers because of a string of birds that have been named after him, including Pallas’s Warbler, Pallas’s Sandgrouse and Pallas’s Reed Bunting. As well as having things named after him, he also named them himself and it was Pallas who named the Harvest Mouse Micromys minutus which translates from the Latin as 'smallest tiny mouse'. Because Pallas was the first person to describe the mouse in a scientific journal, he gets the credit for its discovery and this is why you will often see it written as Micromys minutus (Pallas) in the scientific works that follow strict taxonomic convention.

Sketch of a Harvest Mouse

It was however Gilbert White’s association of the species with the harvest, that gives it the name that we commonly know it by. The French name for it is 'Rat des Moissons' which means the same thing and the Germans call it 'Zwergmaus' literally Dwarf Mouse.

Mammals – The Harvest Mouse in perspective.

There are many texts that describe how the natural world is categorised and named (Linnean classification) and I am not going to repeat it here, but I am going to refer to it, inevitably, in order to describe how the Harvest Mouse fits in with its congeners.

They are members of the Class Mammalia – the mammals. (As opposed to the Class Aves - the birds, the Class Plantae – the plants or the Class Insecta – the insects etc).

The most notable feature of mammals is that they give birth to live babies and suckle their young. The egg-laying mammals of Australia, the Monotremes are classified as being in a sub-class and it is perhaps helpful to qualify the group that we are talking about as being Placental Mammals i.e. possessing a placenta in which the babies are nurtured within the female parent.

Rodents

Rodentia (the rodents) is an “Order” within the Class Mammalia. Other British Orders of the Mammalia are the Carnivora (Fox, Weasel, Badger etc.) the Artiodactyla (deer & cattle etc.), the Lagomorpha (hares and Rabbit), the Pinnipedia (seals, Walrus etc.) the Insectivora (shrews, Hedgehog and Mole) and the Chiroptera (bats). The Marsupalia could also be included as some Red-necked Wallabies may still survive in the wilds of the Peak District, though the order is not naturally represented in Britain.

The Harvest Mouse is a rodent as are all the other mice and rats as well as things as apparently different as the porcupines and as big as the Capybara (65kg or more). The word “rodent” stems from the latin “rodere” meaning to gnaw and they have a deserved reputation for gnawing (though Harvest Mice are not enthusiasts in this regard). All rodents have incisor teeth (two top and two bottom) that are perfectly adapted to the purpose with a layer of hard enamel abutting softer dentine. When they gnaw, the dentine wears away more readily than the enamel, resulting in a sharp wedge-shaped tip and since the teeth grow continuously from the base, throughout their lives, the tooth never wears out. All rodents look as though they should follow dental hygiene practices more thoroughly as their teeth are yellow and this causes concerned enquiries from pet owners about what can be done about it. Yellow is however the natural colour of rodent enamel. With incisors like theirs (and a diet mainly consisting of seeds) who needs canines and pre-molars? Instead, rodents have a gap called the diastema between incisors and molars.

British Rodents

The voles are blunt-faced, short-tailed ground dwellers.

Field Vole Microtus agrestis and Bank Vole Myodes glareolus are widespread and keep owls and Kestrels well fed. The Bank Vole has a rusty tinge to its back fur and has a proportionally longer tail than the Field Vole which is also called the Short-tailed Field Vole

Water Vole Arvicola terrestris - Ratty from Wind in the Willows - lives by water in Britain but in parts of Europe it is seasonally less dependent on aquatic habitats (its scientific name is Arvicola terrestris) At the time of writing there is optimism that their marked population decline is reversing and the “plop” of a submerging Water Vole may once more become commonplace

Guernsey Vole and Orkney Vole Microtus arvalis is a species widespread over Europe but present here only on some of the Orkneys and (possibly as an introduction) on Guernsey. The species is more widely known as the Common Vole.

In Britain voles are classed in the family Cricetidae along with lemmings and hamsters although some authorities put them with the mice and rats in the family Muridae.

Everyone is familiar with at least one of our squirrels:

Grey Squirrel Sciuris carolinensis and Red Squirrel Sciurus vulgaris and most of us know which one we like best; the native British one of course and the Grey should get back where it came from and leave our “cutie” alone. Squirrels are in the family Sciuridae.

Speaking of “cuties”, right on cue, the cutest of them all:

Hazel Dormouse Muscardinus avellanarius and Edible (or Fat) Dormouse Glis glis. Though if you live around Tring where the introduced species of the pair live (the fat one) you may find its endearing qualities are cancelled out by its fondness for gnawing through crucial bits of your home’s infrastructure. The other sleeps a lot and lives in ancient woodlands. Dormice are members of the family Gliridae

The rats need no introduction

Brown Rat Rattus norvegicus and Ship (or Black) Rat Rattus rattus are both species that were unintentionally introduced to this country by humans. The Brown Rat only got here in the 18th century but the Ship Rat, once widespread but now virtually extinct in the UK, is believed to be the vector for the Black Death to Britain in the 14th century and since (though there are serious doubts about this). I was accustomed to Rattus rattus being called Black Rat but there is sense in it being called Ship Rat as it varies in colour.

British Mice

Populations of rodents in the UK
Harvest Mouse

And finally to the “true” mice and a little more detail:

House Mouse
Wood Mouse
Yellow-necked Mouse
Harvest Mouse

These, and the rats (and gerbils) form the family Muridae. There are six species in the British Isles; the two rats and four mice. I used to be confused as to just how many there were because the books often used different names for the same species, but the Field Mouse, the Long-tailed Field Mouse and the Wood Mouse are all the same species and I am going to consistently call it the Wood Mouse (in line with The Mammals of the British Isles; Handbook; 4th edition and most other modern works). Worldwide there are about 730 species of Muridae.

The words “rat” and “mouse” have no scientific justification. Rat is Old English and is used to describe larger members of the muridae, whilst mouse (also originating from Old English) is a term for the smaller members of the family. In practise, as far as Britain is concerned, rats are of the genus Rattus whilst mice are of the genera Apodemus, Mus and Micromys.

House Mouse (Mus domesticus).
This species is probably the most widespread mammal on earth (apart from humans) having been accidentally introduced to every continent and many islands. It originally ranged from Nepal westwards to southern and western Europe where its habitat was rock crevices and it is probably for this reason that it finds buildings to its liking. It doesn’t thrive in natural habitats away from its native range but is closely associated with human habitation and in Britain it is rarely found far into the countryside. In central London they occur in up to 50% of houses and are even more frequent in flats there. It is dull greyish-brown and only slightly paler beneath and as mice go, medium sized, being 70 to 90mm long excluding the tail. Although it is less prone to shredding materials such as paper and wood than Wood Mice, it is more damaging to foodstuffs as it produces copious faeces, leaves urine stains and smells distinctively - of acetamide.

Wood Mouse (Apodemus sylvaticus).
This and the Yellow-necked Mouse are larger than the House Mouse (80-130mm excluding tail). Both are very similar, being dark brown above and whitish beneath and both can have a yellowish patch on the chest which, on the Yellow-necked, reaches across and abuts the upperside. The Wood Mouse’s forebear was present in Europe by the Pliocene and colonised Britain with the retreat of the last ice advance. It is found in woodland and also in many other habitats including arable crops, grassland, roadside verges and gardens. It rarely enters houses but commonly finds outhouses and sheds to its liking, especially if there is a food source there.

Yellow-necked Mouse (Apodemus flavicollis).
As noted above, this species is very like the Wood Mouse though a little larger and the yellow collar is consistently complete. Unlike the widespread Wood Mouse though, this species has a restricted range in England and Wales, being confined to the English-Welsh borders and southern Wales, southern England (east of Dorset) and Essex and southern Suffolk. It is more restricted to woodland and indeed prefers mature, deciduous, ancient woodland. It is more prone to climb and is more likely to enter houses.

Harvest Mouse

The charming and secretive subject of this book. In the introduction, I mentioned that Gilbert White first documented the species. This is how he communicated his find to Thomas Pennant. I make no apology for quoting White’s eloquent writing in full as it describes the species so well.

Extract from Letter X August 4th 1767 to Thomas Pennant

I have had no opportunity yet of procuring any of those mice which I mentioned to you in town. The person that brought me the last says they are plenty in harvest, at which time I will take care to get more; and will endeavour to put the matter out of doubt whether it be a nondescript species or not.

Extract from Letter XII November 4th 1767 to Thomas Pennant

I have procured some of the mice mentioned in my former letters, a young one and a female with young, both of which I have preserved in brandy. From the colour, shape, size, and manner of nesting, I make no doubt but that the species is nondescript. They are much smaller, and more slender, than the mus domesticus medius of Ray, and have more of the squirrel or dormouse colour; their belly is white, a straight line along their sides divides the shades of their back and belly. They never enter into houses; are carried into ricks and barns with the sheaves, abound in harvest; and build their nests amidst the straws of the corn above the ground, and sometimes in thistles. They breed as many as eight at a litter, in a little round nest composed of the blades of grass or wheat.
One of these nests I procured this autumn, most artificially platted, and composed of the blades of wheat, perfectly round, and about the size of a cricket ball, with the aperture so ingeniously closed, that there was no discovering to what part it belonged. It was so compact and well filled, that it would roll across the table without being discomposed, though it contained eight little mice that were naked and blind. As this nest was perfectly full, how could the dam come at her litter respectively, so as to administer a teat to each? Perhaps she opens different places for that purpose, adjusting them again when the business is over; but she could not possibly be contained herself in the ball with her young, which moreover would be daily increasing in bulk. This wonderful procreant cradle, an elegant instance of the efforts of instinct, was found in a wheat-field suspended in the head of a thistle.

The mice were sent on December 4th 1767 as recorded in his Gardeners Kalendar, thus;

Sent two field-mice, a species very common in these parts (tho’ unknown to the zoologists) to Thomas Pennant Esq of Downing in Flintshire. They resemble much in colour ye Mus domesticus medius of Ray; but are smaller than the Mus domesticus vula; seu minor of the same great Naturalist. They never enter houses; are carried into ricks, & barns with ye sheaves, abound in harvest; & build their nests, composed of the blades of corn, up from the ground among the standing wheat; & sometimes in thistles. They breed as many as eight young at one time.

Extract from Letter XIII January 22nd 1768 to Thomas Pennant

As to the small mice, I have farther to remark, that though they hang their nests for breeding up amidst the straws of the standing corn, above the ground, yet I find that, in the winter, they burrow deep in the earth, and make warm beds of grass: but their grand rendezvous seems to be in corn-ricks, into which they are carried at harvest. A neighbour housed an oat-rick lately, under the thatch of which were assembled nearly a hundred, most of which were taken, and some I saw. I measured them, and found that, from nose to tail, they were just two inches and a quarter, and their tails just two inches long. Two of them, in a scale, weighed down just one copper halfpenny, which is about the third of an ounce avoirdupois: so that I suppose they are the smallest quadrupeds in this island. A full-grown Mus medius domesticus weighs, I find, one ounce lumping weight, which is more than six times as much as the mouse above; and measures from nose to rump four inches and a quarter, and the same in its tail.

And this is what Pennant wrote in his 3rd edition of British Zoology Volume 1; 1776

Harvest Mouse
This species is very numerous in Hampshire especially during harvest. They form their nest above the ground; between the straws of the standing corn, and sometimes in thistles; it is of a round shape and composed of the blades of corn. They bring about eight young at a time.
They never enter houses, but are often carried in the sheaves of corn into ricks, and a hundred of them have been found in a single rick, on pulling it down to be housed. Those that are not carried away in the sheaves, shelter themselves during winter underground, and burrow deep, making a warm bed for themselves of dead grass.
They are (except the shrew) the smallest of the British quadrupeds; their length from nose to tail is only two inches and a half; their tail two inches; their weight one sixth of an ounce. They are more slender than the other Long-tailed Field Mouse; their eyes less prominent, their ears naked, and standing out of the fur; their tail slightly covered with hair; their back of a fuller red than the larger species; inclining to the colour of a Dormouse: the belly white; a strait line along the sides dividing the colours of the back and belly.


"The Natural History of Selborne", in which Gilbert White’s edited letters were published in 1788 has never been out of print since. It has comforted soldiers posted abroad and captured the imagination of generations for its evocation of the naturalist Pastor abroad in the rich English countryside. But White was a focussed field naturalist and critical observer as well as being a brilliant, precise writer and if you have not delved into his letters and you are a lover of nature, then you should!