MAMMALS OF UTAH 63 



every seventy-five days under the most favorable condi- 

 tions. Young females have been known to have their first 

 litter when only 103 days old. It has been estimated that 

 under ideal conditions the uninterrupted breeding of a single 

 pair of rats would in three years' time result in the incredible 

 number of 20,185,392 individuals. Of course, such results 

 never happen in nature where various enemies are con^ 

 stantly to be considered ; but it is sufficient warning to those 

 who have heretofore paid no attention to the increase of 

 brown rats in Utah. 



These facts should be borne in mind by everyone : Bu- 

 bonic plague in man is entirely dependent on the disease in 

 the rat ; the infection is conveyed from rat to rat and from 

 rat to man by means of the rat flea ; insanitary conditions 

 have no relation to the occurrence of the plague except so 

 far as they favor the infestation by rats. 



Skunks, weasels and minks destroy rats ; and rat-proof 

 buildings can easily be constructed, the concrete footing be- 

 ing the most important factor. Rats are practically omniv- 

 orous, a few of the things they readily devour being the fol- 

 lowing: seeds, grain, flour, meal, food, fruit, vegetables, 

 mushrooms, bark, bulbs, roots, stems, leaves, flowers, eggs, 

 chicks, ducklings, yoimg pigeons, rabbits, milk, butter, 

 cheese, meat, carrion, mice, rats, fish, frogs, and mussels. 

 (Lantz.) 



Before it is too late every effort should be spent to 

 eradicate this pest, for one must not forget the millions of 

 dollars it cost San Francisco to overcome them. 



HOUSE MOUSE 



MUS MUSCULUS (Linnaeus) 

 Mus musculus Linn., Syst. Nat. I, 1758, p. 62; I, 1766, p. 83. 



Description — Above, grayish brown (mouse color) , lined 

 with blackish ; beneath, ashy plumbeous, tinged with reddish. 

 Tail dusky; feet ashy brown. Total length, 6.5; tail vert. 

 3.2 ; hind foot, 0.70. (Warren.) 



Distribution — The house mouse is common in all set- 

 tled vicinities of the State. 



