(i-2 NINRTEENTH REPORT. 



SOMK (MANGES IN I'lIK LU( AL UISTRIBITIUN OF THK HEKPKTOLOGK AL 



FAtNA. 



Tlie most obvious changes in the habitats of the Douglas Lake region 

 have been those attending the removal of large areas of virgin timber 

 bv cutting, fire, or both. These changes in tlie vegetation of the wood- 

 land habitats have had a direct ett'ect upon tlie fauna of the areas so 

 altered. Where the land has been completely cleared a new forest of 

 aspens has appeared and in the partly cut-over forest areas, the disturbed 

 hardwoods, underbrush which is so conspicuously absent in the virgin 

 timber, berry vines and second growth timber, have come up. These 

 changes affect the upland and forest forms more than the semi-aquatic 

 types of amphibians and reptiles. The fauna from tlie surrounding 

 habitats overflows to some extent into the recently burned-over areas 

 and in the growths of fireweed, Epilobium angustifolium, which are 

 common in burned-over areas during the first two or three years after the 

 fire. Woodland species, Bufo amcricaniis and Rana cantahrigenKis were 

 frequently found near the imdisturbed timber. In the underbrush and 

 second growth timber which follow the fireweed, the grass snake, Liopel- 

 tis vernalis seemed to be increasing in abundance. After the burned over 

 timber had fallen and begun to rot Plethodon erythronotus again appeared 

 in the burned-over areas if there were sufficient vegetation to insure a 

 moist habitat. Rana pipiens and Thamiiophis sirtalis were often seen in 

 rather open burned-over country, but always near some other more favor- 

 able habitat, and as has been noted in another section, these two species 

 were more widely distributed than any other species of tliis fauna. 



The semi-aquatic species seem to have suttered little in the region. 

 Forest fires and the clearing of timber have disturbed the lakes, streams 

 and especially the waterlily associations which are so vital to the success 

 of the primary amj)]iibian species, little if at all. Bogs have been burned 

 over frequently, although the central body of open water usually remains 

 after the bog timber has been destroyed. 



A noticeable exce])tion to the undisturbed condition of the aquatic 

 habitats of the region may be cited as showing how important slight 

 changes may be in determining the local distribution of species. A large 

 number of gartersnakes were collected near a certain beach pool on Sedge 

 Point. Douglas Lake, during the summer of 1915 for use at the Biological 

 Station. Apjiarently correlated witli this destruction of a dependent 

 species of snake during the previous year, was a noticeable increase in 

 the number of young frogs in the same habitat during the summer of 

 1916. Although young frogs, one of the regular items in the food of 

 these gartersnakes in the Douglas Lake i-egion were abundant, few gar- 

 tersnakes were takeji in tliis habitat in 191(i. 



