In towns it hides among stored merchandise, in the hollow walls of buildings, in sewers and other underground passages, or, as in the fields, in burrows which it digs in the ground. Its nests are soft, warm masses of fibrous material which is secured by raids on any available supply of cotton, wool, or fabrics, which they cut into shreds for the purpose.
HARVEST MOUSE
Reithrodontomys megalotis
GRASSHOPPER MOUSE
Onychomys leucogaster
In these retreats it has several litters a year, averaging about ten young, but exceptional cases of more than twenty young have been recorded. The young begin to breed when less than six months old. The size and number of litters increase with the food supply, and under favorable conditions rats soon become intolerable pests.
In Jamaica and the Hawaiian Islands rats became so numerous that sugar-cane and other plantations were at one time threatened with complete destruction. To save the crops the mongoose was introduced, but after checking the rats in Jamaica these curious little mammals in turn became a pest which it appears hopeless to control.
In the Hawaiian Islands the mongoose reduced the number of rats, but the survivors promptly took up their abodes in the tree tops, where they now live as completely arboreal lives as squirrels, safe from their ground-inhabiting enemy.