370 Department of Conservation of Louisiana 



of the state, the toll of muskrat life is severest in extent. 



This indicates that it is not the character of the geo- 

 logical formation itself, which is favorable to muskrats 

 and facilitates their survival during the adverse periods, 

 but the amount of fresh water available to prevent the 

 marshes from becoming too saline and to prevent the 

 marsh fires from burning too deeply, thus destroying 

 the nests or rats and creating alkaline conditions adverse 

 to their development, or, rather, directly to the growth 

 of their food plants. 



Since climatic factors are practically identical both in 

 the Mississippi Valley muskrat territory and in the 

 coastal plain muskrat territory, and since the rats exist 

 similarly in two different types of geological formations, 

 we must look to some other common factor which is 

 favorable to their development and determines their 

 presence in both geological formations. 



The muskrat lands, as stated previously, lie near or 

 adjacent to the Gulf Coast and do not extend any great 

 distance inland. In the inland swamps and marshes away 

 from the Gulf Coast there are no muskrats, and examina- 

 tion of these swamps and marshes will show that they are 

 periodically inundated by the Mississippi river or some 

 other silt-bearing stream. Here there is a clay subsoil, 

 with no appreciable layer of peaty humus on top. The 

 rivers in their land-building process, add layer upon layer 

 of silt and clay during every inundation, but there is no 

 layer of vegetable matter of any consequence developing 

 on top of this soil. 



The Importance of Peaty Humus 



Along the coast, however, even where there is period- 

 ical flooding by the rivers, conditions are such that the 

 salt marsh grasses which thrive in those regions build up 

 a layer of peaty humus from inches to sometimes several 

 feet in thickness. This humus may be as much as 90% 

 vegetable matter and 10% mineral matter, the latter con- 

 sisting of clays and silt, and in some areas a small amount 

 of sea sand. It is in the areas where this peaty formation 

 is best developed that the muskrat seems to thrive best, 



