[45.] 4. Mus l e u c o p u s . (Rafmesque.) American Field-Mouse.
Mus sylvaticus. Forster, Phil. Trans., vol.-lxii. p. 380.
Field Rat, A, American. Pennant, Hist. Quad., vol. ii. p. 185. Arct. Zool., vol. i. p. 131.
Mus Jeucopus. “ Ramkeshue^ maltz, Am. Month. Mag., vol. iii. p. 444; 1810» (quoted from Desmarest,'MVitnm.)
Harlan, Fauna, p. 151. Richardson, Zool. Joum., No. 12. p. 51®.
Mus agrarius. God man, Nat. Hist., vol. ii. p. 88 ?
Appecooseesh. Cree Language.
M . (leucopus), caudd longd vestita, corpore griseo-lutesoente subter ■.abruptS albo, auriculis magnis.
American Field Mouse, with a long hairy tail, hair-brown back, white belly and feet, and large ears.
No sooner is a fur-post established than this little animal becomes an inmate of
the dwelling-houses; whilst the meadow-mouse, described in p. 124, under the name
of Arvicola Penny Ivanicus, at the same time takes possession of the outhouses and
gardens. We observed it as far north as Great Bear Lake; and if the synonyms
prefixed to this article are correctly applied, it is not uncommon in the United
States. It also extends from Hudson’s Bay across the continent to the mouth of
the Columbia River. The gait and prying actions of this little creature, when
it ventures from its hole in the dusk of the evening, are so much like those of the
English domestic mouse, that most of the European residents at Hudson’s Bay
have considered it to be the same animal, altogether overlooking the obvious
differences of their tails and other peculiarities. The American Field-Mouse,
however, has a habit of making hoards of grain or little pieces of fat, which, I
believe, is unknown of the European domestic mouse ; and what is most singular,
these hoards are not formed in the animal’s retreats, but generally in a shoe left
at the bedside, the pocket of a coat, a nightcap, a bag hung against the wall, or
some similar place. It not unfrequently happened that we found barley, which had
been brought from a distant apartment, and introduced into a drawer, through so
small a chink, that it was impossible for the mouse to gain access to its store.
The quantity laid up in a single night nearly equalling the bulk of a mouse, renders
it probable that several individuals unite their efforts to form it. This mouse
does considerable mischief in the gardens, and in a very few nights will almost
destroy a plantation of maize, by tracing the rows for the purpose of collecting the
seeds, and depositing them in small heaps under the loose mould, generally by the
side of a stone, or piece of wood. From the facility with which it seems to
transport the substances it preys upon, I suspected that it had cheek-pouches,
but none were found on examination. The ermine is a most inveterate enemy
to this species, and pursues it into the sleeping apartments.
The Mus leucopus may be considered as the American representative of the
European field-mouse (mus sylvaticus, L inn.), which it greatly resembles, and
perhaps Pennant is quite right in terming it only a variety. The mus sylvaticus
appears to have generally a more tapering, acute tail. Dr. Godman’s description
of the Mus agrarius corresponds so exactly with our animal, that I have quoted it
as a synonym; but the Mus agrarius of Pallas differs, in having small ears. Dr.
Harlan mentions, that several varieties of the mus sylvaticus exist in the neighbourhood
of Philadelphia; but his description, which seems to be a translation
of Desmarest’s account of the European animal, does not agree with any variety of
the mus leucopus that I saw to the north. The varieties that I met with differed
principally in the size of the body, and the length of the tail. Specimens from the
mouth of the Columbia were considerably larger than those from Hudson’s Bay.
DESCRIPTION.
The American Field-Mouse has a larger head than the English domestic mouse; but in its
general form it is similar to that animal. On the other hand, its- head is smaller than that
of Wilson’s meadow-mouse; its body less fleshy, and it weighs less. Its muzzle is rather
sharp. The whiskers are much longer than the head, part of them are black, the rest white.
Eyes moderately large. Ears large, erect, membranous, of an elliptical form, with rounded
tips, and covered rather thinly with short adpressed hairs.
The fu r of the body is very fine, but not long, and is throughout of a dark, bluish-gray
colour from the roots to near the tips. The colour of the upper parts is hair-brown, darkest
on the crown of the head, and along the back; the sides are of a lighter hue, approaching to
yellowish-brown, or sometimes, together with the hips, to reddish-brown. The cheeks have a
still more lively colour than the sides, being somewhat rufous. The upper lip, a space on
each side of the mouth, the chin, all the under parts, the inside of the thighs, and the whole
of the legs and feet,, are white..
The tail is thickly clothed with short hairs lying pretty smoothly, no scales whatever being
visible. Its upper surface is of a hair-brown colour, considerably darker than any other part
of the animal, and contrasts strongly with the inferior surface, which is white; the line of
contact of the two colours is straight and well defined.
Fore-feet, with four toes and six tubercles on the palm. Of the three anterior tubercles,
one is seated at the common origin of the two middle toes, and one at the commencement of
each of the other two toes, which arise farther back. The other three tubercles lie nearly in
a line at the posterior part of the palm. The smallest of these is the interior one, and it
occupies the usual site of the thumb, of which there is no other vestige,—not eVen a nail.