Feb. 23, 1924 
Life Habits of Meadow Mice 
529 
these were confined to one acre of. ground, this would mean a little more 
than 20 mice to every square foot. 
MATING 
“Mating” is only for the immediate needs, and a misnomer at that, 
because a female usually accepts the attention of any number of males 
in rapid succession and shows no choice of individuals, favor to young 
or old, or any regard to relationship, whether sire or brothers or previous 
offspring. There seems to be no moral necessity of life with them other 
than the most rapid increase possible of individuals of the species. The 
one exception to complete promiscuity is provided by nature in the slower 
sexual development of the males, which prevents inbreeding within the 
litter before the young have scattered, the males not coming to sexual 
maturity until about the time the first young of the females of the same 
litter are bom. Furthermore, respect for the females during pregnancy 
by even the most virile old males is enforced with such spirit that it 
seems never to be questioned. 
When a half-grown female jumps and squeaks at an old male, he cringes 
or runs, for he knows that her teeth are sharp and that she will not hesi¬ 
tate to use them. If he comes too near her newly bom young, the mother 
will sometimes punish him severely before he can get out of reach. If the 
very young are left unguarded, the males or other members of the family 
will often kill and eat them or sometimes wantonly bite and kill them all 
before their mother returns. In crowded cages it is difficult to prevent 
the young from being killed, but the mother is a model of care and solici¬ 
tude, ready to fight to the last for them and to use all her intelligence and 
energy in their protection. 
NESTS 
The female builds a new nest for the reception of the young, endeavor¬ 
ing to place it where none can find it, but if discovered and disturbed 
she promptly removes the young to a place of safety. If suddenly 
alarmed she often rushes out with all of the young clinging for dear life 
to her nipples and drags them for some distance along the runway or 
under cover, where she can gather them and carry them one at a time 
in her mouth to another nest. So quick and shuttlelike are her motions 
that the young disappear as if by magic, and when one nest box is dis¬ 
turbed the young will all be found a few moments later in another. 
In cold weather the nest is built especially thick and warm, and the 
newly bom young are not left for more than a few moments at a time, 
and then the mother covers them up securely before she leaves them. 
One old mother in No. 3 cage had a new family one cold night in 
March. In the morning she was very hungry for her breakfast when it 
was placed in the cage, but was greatly worried about the young getting 
cold if she left them for a minute. She rushed out of the nest box and 
back several times without stopping to eat, and seemed greatly disturbed. 
Suddenly she rushed up to her one remaining young of the previous 
litter, then 22 days old, well furred and nearly half grown, seized it in her 
mouth and carried it into the nest, and leaving it with the tiny naked 
babies, returned to the food. The foster mother soon reappeared at the 
breakfast table but was instantly grabbed up, rather roughly, and with 
many squeaks carried back into the nest, where this time it remained 
while the real mother finished her breakfast. 
