236 College of Forestry 
Ondatra zibethicus (Lann.). Muskrat. 
The muskrat has long been known as an enemy of the 
clam or mussel bed, the large piles of empty shells so com- 
mon on the shores of our lakes, ponds, and rivers being 
eloquent witnesses of this animal’s insatiate appetite for the 
luscious bivalve. The importance of this class of food is 
variously estimated. Some of the estimates given by a few 
authors are given below: 
Seton (1909, I, p. 554) states that vegetable food is taken 
by preference, but that it also eats clams, fish, insects, and 
even young birds. Lantz (1910, p. 16) says “ In the winter 
the chief food of muskrats consists of the roots of aquatic 
plants — pond lilies, arum, sedges and the like — but in 
some loealities the animals feed on mussels and also on carp 
and other sluggish fish that bury themselves in mud.” 
Merriam (1886, p. 275) states that ““ They are extremely 
fond of the fresh-water mussels (Unio and Anodon) and 
large quantities of empty shells may often be found near 
their homes.” To just what extent mussels are eaten as 
compared with other food is not stated; nor it is known, so 
far as known to the writer, at what season the molluscan 
diet is used to the greatest extent. The method of opening 
the shells has long been a mooted question. Adams (1908, 
p. 408) found the muskrat plentiful at Isle Royale. After 
stating the fact that little is known on this subject he quotes 
from Kennicott (1857, p. 106) who says “ Collecting them 
(mussels) from the bottom, it carries them in its teeth to a 
log or stone, where, sitting upon it haunches, and grasping 
them in the fore-paws, it opens the shells with the incisors 
as skillfully as it could be done with an oyster-knife. I have 
observed that those species with thin shells are more sought 
for, and have often found large specimens of Unio 
[Quadrula| plicatus unopened among the piles of empty 
shells, the muskrat apparently considering them not worth 
the trouble of gnawing apart the valves at the back, in which 
manner the heavy shells are sometimes opened. ” (Lantz, 
1910, p. 17) states that “ One frequently comes upon heaps of 
