are becoming less optimum for it (John J. Lynch, verbal conmunica- 
tion). The probability exists that the environmental changes 
outlined above way have had much to do with the losses of some of 
the larger emergent plants which have been noticed in southwestern 
Lovisiana during the 1950's. Nutria, in this complex and dynamic 
habitat, do not appear on the whole to be a decisive factor among 
those already affecting the marsh vegetation. 
SUMMARY AND CONCLUSIONS 
A study of the effect of nutria on marsh vegetation was made 
in southwestern Louisiana from 1954 to 1956 by means of plant 
transects, exclosures and indices to nutria abundance. 
Nutria populations were high on most of the transects through 
the summer of 1955 and declined thereafter. The proportion of 
openings in the vegetation of three of the transects decreased 
slightly from 1954 to 1955 and to a greater extent from 1955 to 
1956. The proportion of openings remained the same for one tran- 
sect and increased on a fifth transect because of the gradual 
dying-out of the vegetation. The feeding habits of nutria are 
shown to be conducive to wasteful use of the vegetation. 
Nutria feeding had little permanent effect on saltmeadow 
cordgrass and no effect on mature sawgrass of the stands studied. 
Nutria thinned.stands of Olney's three-square, but this effect 
seems to be less critical than that of habitat factors. The 
reed stands studied were utilized but unaffected by nutria; 
30 
