The Fur Animals of Louisiana 371 



other factors being practically equal in the different geol- 

 ogical areas of the state. Therefore, since the abundance 

 of muskrats seems to be in the direct proportion to the 

 amount of peat in their habitat, it would seem then that 

 the one outstanding factor of a favorable muskrat en- 

 vironment is the presence of this peat. This peaty forma- 

 tion consists largely of accumulated dead remains of the 

 .sedges and grasses characteristic of that region, in which 

 are intermingled the roots of the living plants which 

 form the chief source of food for this mammal. 



Plants Forming Peat Lands 



Among the more important plants whose rooting sys- 

 tems built up this peaty formation might be mentioned 

 the three-quare rushes (Scirpus robustus, S. olneyi and 

 .S. americanus) ; the Giant bulrush (Scirpus validus); Saw 

 grass (Cladium effesum) ; the Cattail (Typha angusta- 

 folia); Couch grass (Spartina patens juncea) and a number 

 of others. As to the importance of this layer of peaty 

 humus in protecting the muskrats from adverse condi- 

 tions there are several distinct benefits that may be de- 

 rived therefrom. In the first place, it enables the animals 

 to build their uncler-water runs without difficulty, since it 

 is more easy for them to dig through a spongy layer than 

 through a layer of clay or sand. This spongy layer sus- 

 tains the underground tunnels of the muskrats and pre- 

 sents caving. Muskrats in making the runs from the nests 

 dig deeply down from the nest under the water and 

 come up to the surface at a considerable distance from 

 the nest. These efficient water traps (plunge holes) and 

 their radiating subterranean tunnels prevent access of 

 natural enemies of many kinds. 



