BUREAU OF BIOLOGICAL. SURVEY. 551 



tion of methods of destrojnng the gophers recommended by the Sur- 

 vey, there has not been a single break. 



In some localities, as on the Ziini Reservation in New Mexico, kan- 

 garoo rats also burrow in canal banks and cause breaks. During the 

 year these dike injuries were investigated and recommendations for 

 the destruction of the manmials were made, the adoption of which, it 

 is believed, will prevent further injuries. 



PRAIRIE DOGS. 



Prairie dogs are confined to the States of the Middle West, where 

 in certain regions the}' do great damage to the forage grasses and 

 other vegetation. During the year experiments have been undertaken 

 by assistants of the Survey in Arizona, Colorado, Wyoming, Mon- 

 tana, and New Mexico to determine the best and cheapest method of 

 poisoning these animals, especially in summer. In fall and winter, 

 when green food is scarce, it is comparatively easy to destroy large 

 numbers by poisoned grain prepared according to a formula worked 

 out by the Survey. In summer, however, when the animals are most 

 active and most destructive and grass and other green food abounds, 

 it is very difficult to induce them to eat poisoned grain. On account 

 of the varying conditions of the natural food supply, further experi- 

 ments Avill be necessary before final recommendations can be made. 



SEED-EATING MAM:MALS IN RELATION TO FORESTRY. 



One of the most serious problems connected with the reforestation 

 of treeless areas within the National Forests is the protection of 

 newly planted seeds and young trees from the attacks of birds, mice, 

 gophers, ground squirrels, rabbits, and other rodents whose depreda- 

 tions collectively continue the year through. This is especially true 

 when the only practicable means of reseeding is bj^ broadcast sowing. 

 In certain areas within the Black Hills National Forest the losses 

 of seed after sowing have amounted during the past year to as much 

 as 50 and even 75 per cent. Accordingly the cooperation of the Sur- 

 vey was requested by the Forest Service in an attempt to devise 

 methods of protecting seeds and saplings from such attacks. Hence 

 two assistants visited the Forests where replanting is being conducted 

 on a large scale to experiment with various protective coatings for 

 seeds and also with traps and poisons. The former proved unsuc- 

 cessful, but attempts to poison the mice and ground squirrels, the 

 chief culprits, proved very successful. The baits recommended are 

 oatmeal mixed with strychnine and water, and wheat coated with 

 hot tallow mixed Avith strychnine as a protection against moisture. 

 By distributing the poisoned bait several days in advance of the 

 planting, the loss of seed is reduced to a minimum. 



COOPERATION WITH THE PUBLIC HEALTH AND IVIARINE-HOSPITAL 



SERVICE. 



At the request of the Chief of the Public Health and Marine- 

 Hospital Service Prof. D. F. Lantz furnished several chapters for a 

 report by that Bureau entitled " The rat in its relation to the pub- 

 lic health." These chapters are: "Natural history of the rat;" 

 " Natural enemies of the rat; " and " The rat as an economic factor." 



