within a limited geographic area, however, subtle differences in 

 habitats are important to muskrat distribution and abundance. Recent 

 interest in the estuarine environment has prompted a comprehensive 

 evaluation of the wetland habitat in coastal Louisiana. The report 

 is an outgrowth of that study and attempts to classify the marsh 

 vegetative types and their potential role in the production of muskrats. 



Muskrat populations were significantly higher in brackish marshes than 

 in the other types surveyed. An average of 72.6 percent of the total 

 muskrat houses counted were located in brackish marsh. Although the 

 percentage values were approximately equal for southeastern and south- 

 western Louisiana, population densities were much higher in the 

 southeast. Saline marshes in the southeast contained populations 

 approximately equal to the overall average density. In the southwest, 

 however, saline marshes appeared to be yery poor muskrat habitat, 

 possibly because of their well-drained nature. Intermediate transition 

 marshes had below-average population densities, but were average or 

 high in restricted areas adjacent to the brackish type. Fresh marshes 

 exhibited the lowest muskrat population densities of any of the types 

 surveyed. Although they comprised 31.4 percent of the total area 

 studied, they averaged only 4.1 percent of the muskrat houses counted. 



Highest house counts occurred in February when water levels were 

 generally high, temperature was low, and the spring breeding season begins. 

 These factors are undoubtedly responsible for the increase in the 

 number of muskrat houses observed at this time. Tunneling, either 

 in spoil levees or in the peat soils, was not considered a significant 

 factor in calculating muskrat populations in the coastal marsh area. 

 In other situations, however, this factor could significantly alter 

 population estimates. 



Catch figures indicate that the average production of muskrats can 

 be estimated by multiplying the number of active houses by three. 

 The average catch ranged from 2.67 to 3.41 muskrats per house and 

 averaged 3.19. Earlier studies using quotas of estimated total 

 muskrat populations yielded similar results. Body measurements 

 revealed that tail length was closely correlated with the size of 

 the muskrat and that tails alone could be used to estimate the size 

 composition of a given muskrat population. (G.S.) 



Keywords: muskrats, marsh vegetation, coastal marshes, Louisiana 



V-C-4 



O'Neil, T. 1949. The muskrat in the Louisiana coastal marshes. Louisiana 

 Department of Wildlife and Fisheries, New Orleans. 152 pp. 



The findings presented in this book are the result of studies made 

 by the author during a five-year period from 1940 to 1945, The 

 major portion of the book is a study of the ecology, population 



242 



