THIRTY-NINTH BIENNIAL REPORT 55 



soil erosion, maintenance of a continuous flow of the stream during the 

 low water period of the year, and restoration of the large stream irri- 

 gated meadow for livestock. Stream improvement has developed addi- 

 tional fishing waters where there was practically none prior to the intro- 

 duction of the beaver. By 1941, numerous fishermen from various parts 

 of the State were enjoying excellent fishing from waters impounded 

 behind a series of 30 beaver dams over a distance of 1^ miles. The distri- 

 bution of surplus animals from this location to other streams where their 

 accomplished results have been equally as favorable and of much interest 

 to landow^ners and agencies faced with the problem of land utilization. 



Another outstanding demonstration is the colony of beaver intro- 

 duced into Ackerson Creek, Tuolumne County, early in 1940. Only three 

 animals were used to start this experiment. The stream bed was eroded 

 to the degree where the water table had dropped very low and was of 

 practically no value for subirrigation to an adjacent 400 acre meadow 

 along both banks of the stream. The meadow no longer was suitable for 

 livestock and the stream was drying up for a short period in the summer 

 months. By 1944, the beaver had constructed a series of 18 dams down 

 the length of the meadow. The stream was flowing continuously through- 

 out the year, the water table was again normal, and the meadow was 

 restored, furnishing grazing for livestock. The stored water back of the 

 beaver dams was creating habitat for fishlife and many limits of fish 

 were reported taken b}^ fishermen. 



Another example of stream improvement by transplanted beaver 

 is Smithueck Creek in Sierra County. Five animals were transferred 

 there in July of 1943 from Rowland Creek, Plumas County. In June of 

 1946 the animals had constructed eight large dams. The impounded 

 waters were raising the water table in the lands adjacent to the beaver 

 ponds, creating a better growth of grass for stock grazing. Fishermen 

 report an increase in the size and numbers of fish caught since the 

 addition of the beaver dams in the stream. Ducks have been observed 

 nesting in the vicinity of the ponds for the past two seasons. 



The restoration and introduction of these valuable animals is being 

 administered with caution as regards other interests and any definite 

 conclusions regarding the economic value of the animals are stated with 

 reservations. However, if certain facts and opinions obtained so far 

 are indicative of benefits to be derived with proper management, it will 

 justify artivities on a much larger scale in the future. 



PARASITES AND DISEASES 



In August, 1945, the disease laboratory staff moved into new quar- 

 ters located in Strawberry Canyon on the campus of the University of 

 California in Berkeley. This has greatly facilitated our work but with 

 the end of the war and the return of service men to the staff, as well as the 

 expansion of our program, the facilities are again proving inadequate 

 and crowded. 



Studies on deer in the coastal counties presented further evidence 

 that the parasites of the digestive tract are the chief cause of losses, 

 particularly among fawns and yearlings, while the mule deer of the 

 northeastern portion of the State, including the winter deer herd which 

 migrates into our State from Oregon, apparently are not greatly infected 



