SMALLER MAMMALS OF NORTH AMERICA 



395 



whenever it jumps it is thrown into a series of 

 somersaults, turning helplessly over and over 

 in the air. 



The jumping mice form a small group of 

 species and geographic races closely similar in 

 general appearance. They are the sole repre- 

 sentatives in North America of the Old World 

 jerboas and are themselves represented else- 

 where by a single species occurring in the inte- 

 rior of China. The jerboa family contains in 

 addition many larger and curiously diverse spe- 

 cies distributed over a large part of Asia, 

 Africa, and southern Europe. Many Old 

 World jerboas are desert animals, some of 

 them exact reproductions in shape and color of 

 the kangaroo rats of arid regions in the West- 

 ern and Southwestern States and Mexico, al- 

 though they are in no way related to those 

 animals. 



Jumping mice are distributed over most of 

 the northern parts of North America from the 

 Atlantic coast of Labrador to the Bering Sea 

 coast of Alaska, and southward to North Caro- 

 lina, Illinois, New Mexico, and California. 

 They are nocturnal in habits and live in or near 

 the borders of forests, in thickets of weeds or 

 brushwood, and in meadows adjoining wood- 

 land areas or. forest lakes. In prairie country 

 they occupy belts of woody growth bordering 

 streams. In congenial locations they range 

 from sea level up to an altitude of 8,000 feet 

 or more. 



For winter homes they dig burrows two or 

 three feet deep, in the lower parts of which 

 they excavate oval chambers and fill them with 

 fine grass and other soft material to make a 

 warm nest. Other chambers opening from 

 these burrows serve as store-rooms for berries, 

 seeds, and nuts of various kinds, among which 

 beechnuts are a favorite. 



The nests occupied as summer homes are 

 placed in shallow burrows a few inches below 

 the surface of the ground, or they may be in 

 a hollow tree, under a piece of bark, in a dense 

 tussock of grass, or in other makeshift shelter. 

 In these nests the young, varying from two to 

 eight in number, are born at varying times be- 

 tween May and September, indicating the prob- 

 ability that more than one litter is produced 

 each season. 



When suddenly startled from her nest the 

 female often flees with several of the young 

 clinging to her teats. She runs swiftly through 

 the grass, and if hard pressed will take a long- 

 leap, still carrying the pendant young. It is 

 surprising that such delicately formed animals 

 can make long leaps in thickly grown places 

 and apparently land safely, especially when 

 carrying their young. In the flights of the 

 mother some of the young must be jarred 

 loose, but when the alarm is over no doubt 

 she returns to find and rescue any that may 

 be missing. 



In the northeastern States jumping mice are 

 common habitants of meadows. They are 

 equally at home in the rocky meadows of New 

 England, on the flower-spangled borders of 

 rushing trout streams in the Sierra Nevada of 

 California, and the boggy glades of subarctic 

 Alaska. 



My first acquaintance with them was made 

 many years ago, during haying time, in north- 

 ern New York. Hidden under a haycock, as 

 the last forkful was raised one of them was 

 often revealed, and its startling leaps always 

 resulted in an exciting chase, which usually 

 ended in the escape of the strange little beast. 



Unlike most of their small fellows of 

 meadow and thicket, jumping mice regularly 

 hibernate, occupying the nests near the bot- 

 toms of the winter burrows. They usually be- 

 come fat on the abundance of food at the end 

 of summer, and in September or October, with 

 the approach of cool weather, enter their win- 

 ter quarters and sink into the long, hibernat- 

 ing lethargy. Sometimes two of them are 

 found hibernating in the same nest. 



During hibernation they are coiled up in 

 little furry balls, the nose resting on the abdo- 

 men, the hind feet on each side of the head, 

 and the tail wound around the body. The 

 winter sleep usually lasts until spring, but may 

 be broken at any time by mild weather. 



When hibernating the mice appear cold and 

 lifeless, but if one is carried into a warm 

 house or even held a long time in the captor's 

 hands it will slowly awaken and may become 

 as lively as in summer. When returned to a 

 low temperature, however, it soon resumes its 

 mysterious seasonal sleep. 



THE SILKY POCKET MICE (Perog- 



nathus flavus and its relatives) 



{For illustration, see page 413) 



Soft, shining fur, delicate coloring, and 

 graceful form distinguish the silky pocket mice 

 from others of their kind. The family of 

 which they are members consists of rodents 

 peculiar to America and includes many other 

 species of pocket mice and kangaroo rats. All 

 are provided with little pouches on each side 

 of the mouth for gathering and carrying food, 

 have proportionately long tails, and hind legs 

 and feet more or less developed for jumping. 

 Only in the most remote way, however, are 

 they related to the jumping mice of the jerboa 

 family. 



The silky pocket mice vary in size from the 

 tiny yellow species pictured on the accompany- 

 ing plate, which weighs much less than an 

 ounce, to forms considerably larger than the 

 common house mouse. The little yellow pocket 

 mouse is one of the smallest mammals in the 

 world, and in addition is one of the most beau- 

 tiful of our small species. Its bright eyes and 

 the delicacy of its form and color, combined 

 with the readiness with which, in most in- 

 stances, it appears to lose all fear when caught 

 and gently handled, render it extremely at- 

 tractive. 



As with the majority of other pocket mice, 

 the silky-haired species are limited to the more 

 arid parts of North America, and range from 

 the Great Plains west of the Mississippi Val- 

 ley to the eastern base of the Cascades, to the 

 Sierra Nevada, and farther southward to the 

 Pacific coast, and from the Canadian border 

 to the Valley of Mexico. Vertically, the range 



