88 YEARBOOK OF THE DEPARTMENT OF AGRICULTURE. 



much less eonmion in tlie case of inanimals and birds than among- the 

 smaller j)lants and insects, and species which have gained a foothold 

 in distant lands have almost always been intentionally introduced. 



Certain small mammals have, however, accidentally found their way 

 in vessels from one port to another. Two or three si^ecies of rats 

 and the house mouse of Europe have thus become widely dispersed 

 over the globe. Fruit vessels plying between j)orts of the United 

 States and Central or South America occasionally bring snakes, 

 small mammals, and insects in bunches of bananas. In November, 

 1895, a Central American mouse, of the genus Oryzomys, concealed in 

 a bunch of bananas shipped from Puerto Limon, Costa Rica, was cap- 

 tured alive in a commission house in Washington, D. C. A young 

 murine opossum from tropical America was discovered in a bunch of 

 bananas at Ames, Iowa, during the summer of 1882, and was kej)t 

 alive for some time. If such cases were frequent, it can be readil}" 

 seen how a species might gain a foothold in new regions, provided 

 the conditions were favorable for its increase. 



During the last fifteen or twenty years Bering Island, one of the 

 Commander grouj) in Bering Sea, has been overrun with the com- 

 mon Siberian red-backed mouse (Evotomys rntllus). This species 

 was formerly unknown on the islands, but has been introduced since 

 1870, probably in firewood brought from Kamchatka. Within ten 

 years it spread all over the island from the beaches to the mountains 

 in the interior. It occurs both in the swam-ps and on the sand dunes, 

 and has become a pest in the huts of the natives. In 1889 it was still 

 confined to Bering Island, but will probably reach Copi3er Island in 

 time. 



DOMESTICATED SPECIES MAY BECOME NOXIOUS. 



Domesticated animals, like cultivated plants, may run wild and 

 become so abundant as to be extremely injurious. Wild horses are 

 said to have become so numerous in some parts of Australia that they 

 consume the feed needed for sheep and other animals, and hunters are 

 emi^loyed to shoot them. In some of the Western States they have 

 also become a nuisance, and in Nevada a law was passed in 1897 per- 

 mitting wild horses to be shot. Recent reports from Washington 

 indicate that cayuses are considered of so little value that they are 

 killed and used for bait in poisoning wolves and coj^otes. 



Pigs have run wild in some of the Southern States and also on cer- 

 tain islands, where, as on the Galapagos, they were originally intro- 

 duced to furnish food for crews of vessels in need of fresh meat. 

 According to Dr. Finsch,^ they were introduced into New Zealand by 

 Captain Cook about 1770, and soon becoming wild, increased to a 

 remarkable degree. A century later wild pigs were so abundant in 

 the flax thickets of the i^rovince of Taranaki, on the North Island, 



' Globus, LXIX, 1896, Nr. 2. 



