MIGRATIONS OF EATS. 17 



In nearly all countries a seasonal movement of rats from houses 

 and barns to the open fields occurs in spring, and the return move- 

 ment takes place as cold weather approaches. The movement is 

 noticeable even in large cities. 



But more general movements of rats often occur. In 1903 a 

 multitude of migrating rats spread over several counties of western 

 Illinois. They were noticed especially in Mercer and Rock Island 

 counties. For several years prior to this invasion no abnormal 

 numbers were seen, and their coming was remarkably sudden. An 

 eyewitness to the phenomenon informed the writer that as he was 

 returning to his home by moonlight he heard a general rustling in 

 the field near by, and soon a vast army of rats crossed the road in 

 front of him, all going in one direction. The mass stretched away 

 as far as could be seen in the dim light. These animals remained 

 on the farms and in the villages of the surrounding country, and 

 during the winter and summer of 1904 were a veritable plague. A 

 local newspaper stated that between March 20 and April 20, 1904, 

 Mr. F. U. Montgomery of Preemption, Mercer County, killed 3,435 

 rats on his farm. He caught most of them in traps. a 



In 1877 a similar migration occurred into parts of Saline and 

 Lafayette counties, Mo.; 6 and in 1904, one came under the writer's 

 observation in Kansas River valley. This valley for the most part 

 was flooded by the great freshet of June, 1903, and for about ten days 

 was covered with several feet of water. It is certain, that most of 

 the rats in the valley perished in this flood. In the fall of 1903 much 

 of the district was visited by hordes of rats, which remained during 

 the winter, and by the following spring had so increased in numbers 

 that serious losses of grain and poultry resulted. 



No doubt the majority of the so-called migrations of rodents are 

 in reality instances of unusual reproduction or of enforced migration 

 owing to lack of food. In England a general movement of rats 

 inland from the coast occurs every October. This is closely connected 

 with the closing of the herring season. During the fishing, the rodents 

 swarm to the coast, attracted by the offal left from cleaning the 

 herring; and when this food supply fails, they hasten back to the farms 

 and villages. 



In South America periodic plagues of rats have taken place in 

 Parana, Brazil, at intervals of about thirty years, and in Chile at 

 intervals of from fifteen to twenty-five years. These plagues in 

 the cultivated lands follow the ripening and decay of the dominant 

 species of bamboo in each country. The ripening of the seed furnishes 

 for two or more years a favorite food for rats in the forests, where 



aMoline (111.) Evening Mail, April 25, 1904. 

 b Forest and Stream, vol. 8, p. 380, July 12, 1877. 

 81155— Bull. 33—09 3 



