230 



MAMMALS OF AMERICA 



bish accumulating along the fences year after 

 year as a harbor for various rodent and insect 

 pests. If these borders were burned yearly, 

 mowed and raked, treated with oil or chemicals 

 to prevent weed growth, closely pastured, or 

 thoroughly cultivated, the hawks and owls 

 would quickly dispose of the rodents, which 

 would then have no protecting cover." 



Like the Rabbits and \'arying Hares, Cotton 

 Rats have their periods of abundance ; and some- 

 times their increase assumes the proportions of 

 a veritable plague. Mr. H. P. Attwater thus 

 tells of one of these " invasions " : " In the year 

 1889, Signiodons appeared suddenly in this 

 (Bexar) county in great numbers, and were 

 known as ' tramp Rats.' Where they came 

 from, or from which direction, I have been 

 unable to find out. Thousands first appeared 

 about the first of May, and were heard from in 

 all the region for many miles around San Anto- 

 nio. They made their nests with the Wood Rats 

 in the bunches of Opuiitia, with a network of 

 runways leading in every direction, through 

 which they were often seen running in the day- 

 time. They seemed to agree with the Wood 

 Rats, but in the oat stacks and around the ranch 



buildings the common Brown Rats fought, 

 killed, and ate them. Mr. Watson's boys killed 

 over one hundred in one afternoon in a brush 

 fence, and for several months their cat used to 

 bring in from six to twelve every night. He 

 says that on one occasion, when the rats were 

 thickest, they counted thirty-eight which this 

 cat in one night had piled up in the wood box 

 for the amusement of her kittens. The bulk of 

 these Rats stayed for about eighteen months. 

 After the crops were gathered they began to get 

 scarce, and gradually disappeared. ^^■hether 

 they died out or ' tramped ' out I am unable to 

 say, but I am inclined to think many of them 

 migrated." 



Cotton Rats are very prolific, the females pro- 

 ducing eight, and occasionally eleven young at 

 a birth. They have a host of enemies. Hawks 

 sit on the telegraph and fence posts and watch 

 for them, frequently diving into the grass for 

 their prey ; barred owls " remove " them nightly, 

 and short-eared owls migrating northward 

 stop over to feast upon them. \\'easels, .Skunks, 

 dogs, and cats hunt them ; and rattlers and other 

 snakes, distributed in their retreats, have been 

 " found gorged with Cotton Rats." 



RICE RAT 

 Oryzomys palustris {Harlan) 



Other Names. — Rice Field Mouse. Marsh Mouse. 



General Description. — A rather large Mouse with 

 a much heavier body than the common House Mouse. 

 Head of moderate proportions ; nose pointed ; ears of 

 medium size nearly buried in the fur and clothed with 

 short hairs; body slightly thick-set; feet of normal pro- 

 portions ; hind feet large ; soles naked ; tail scantily 

 haired, about half of total length; general color above, 

 dark brown to pale brown; below grayish; hair rather 

 coarser than that of the House Mouse. 



Dental Formula. — Incisors, ^^ ; Canines, -~~ ; Pre- 



I— I ' ' 0—0 * 



molars, ^^^ ; Molars, =^^=16. 

 0—0 ' 3—3 



Pelage. — Adults : Sexes identical. Seasonal varia- 

 tion while present not especially noticeable. Above, 

 dark-brown shading into pale-brown, washed with huffy 

 on sides ; grayish beneath, the hairs with plumbeous 

 bases and tipped with white, but with grayish underfur 

 showing through ; tail above dark, below pale, very 

 scantily haired; feet whitish. Young: Slate gray. 



Measurements. — Total length. 8.8 inches ; tail verte- 

 lirac, 4.4 inches ; hind foot, slightly over i inch. 



Range. — New Jersey to Georgia. 



Food. — Seeds, grasses and various plants. 



Remarks. — An extensive group which ranges from 

 New Jersey southward over a large part of South 

 America. In the United States only a few species and 

 subspecies, four in number, come under consideration. 

 These four differ only in minor details. 



Relateo Species 



Rice Rat. — Oryzomys palustris palustris (Harlan). 

 Tyi)ical animal as described above. New Jersey to 

 Georgia, westward to eastern Texas. 



Texas Rice Rat. — Oryzomys aquaticus Allen. Large; 

 feet small ; yellowish-brown above. Southeastern 

 Texas. 



Florida Rice Rat. — Oryzomys natator natator 

 (Chapman). Largest of the United States Rice Rats; 

 coloration darker. Florida west to Texas. 



