SHIRAS EXPEDITIONS TO WIIITEFISH F'OIXT. 110 



ne7isis (Bailey) will be a;ivt'u in this paper, for this species is related 

 to the nsh life of the marsh Uikes in an especially important ecologi- 

 cal way. 



The work of h(>avers was very manifest almost everywhere about 

 tlie marsh pools. These were in the form of lodges (Ruthven, 1914), 

 submerged piles of sticks gathered for food, felled trees, dams (Plate 

 XVB), and networks of channels through the marshes. The dam on 

 Mason's Creek was a new one, and above it a large pond had been re- 

 cently formed; this had many dead trees standing in the water, as well 

 as dying ones with wilting leaves. Forest conditions are rapidly chang- 

 ing to pond conditions here; and thus a new dwelling place for fish will 

 in all probal)ility be formed. The marsh lakes appear to be very 

 good habitats for l)eavers. Both the marsh and lake region are readily 

 accessible one from the other by the animals, and bj- means of channels 

 they can easily get to wooded areas where there is an abundance of 

 food in the way of young trees. 



Climatic Features. 



The climate of the Whitefish Point region is probably that of north- 

 ern Michigan generally with, a little more than the usual rainfall due to 

 its proximity to Lake Superior. According to data given by Leverett 

 (1911), the mean annual temperature of the Northern Peninsula is near 

 40° F, with a few^ days when it exceeds 90° F, and a few when it is below 

 20° F. In August, the average temperature is near 60° F. The rain- 

 fall is near 34 inches each year; at Whitefish Point it varied from 'ess 

 than 25 inches to near 30 inches from 1906 to 1910, inclusive. There 

 is considerable snow, and winter conditions last usually from early 

 November to late April. The small lakes are frozen over during this 

 time. The Avarm season is, therefore, short, with spring, summer, and 

 autumn conditions from May to October. There is an abundance of 

 sunshine, and the periods of daylight are from 3 A. M. to 9 P. M., a 

 length of time favorable for plant growth. 



In August, 1913, when most of the fish Avork was done, the weather 

 was, for the most part, pleasant with days mostly warm and sunny and 

 nights cool and clear. There was a rainy day or two and a few showers 

 of short duration. The season was called by residents a wet one. 

 From July 15, 1913, to Augu.st 28, 1913, the range of temperature 

 readings at the Life Saving Station on Lake Superior beach were from 

 38° F. to 89° F. With the permission of the U. S. Lif(> Saving v^ervice, 

 these readings are published here: 



