buggies are promptly utilized. Any agency such as drought, graz- 
ing, muskrat and goose eat-outs (Lynch et al., 1947), hurricanes 
and marsh buggy activities (Harris and Chabreck, 1958), that thins 
or destroys vegetation, appears to improve the habitat for nutria. 
Man's activities, as well as natural events, may have been a fac- 
tor in determining the numbers of nutria in the marshes of south- 
western Louisiana. 
Man's activities and natural events provide other factors 
(which we did not study) that have caused changes in the marsh 
and probably have affected the marsh vegetation. A brief review 
of these factors illustrates the dynamic and complex nature of the 
marsh habitat which makes it unlikely that any one species of 
animal can be the sole cause of a noticeable ecological change. 
A drought of at least four years ended with 1955. Ifa 
retardation of one year is permitted, the vegetational changes 
also correlate roughly with rainfall. During the drought period 
the accumulated deficiency was approximately 7O inches, 10 inches 
more than a nomai year's precipitation, and during 1954 it was 
20 percent of normal. Rainfall during 1955 was near normal, 
and a deficiency of 7 inches was recorded for the first half of 
1956. Precipitation varies locally on the coastal marshes, but 
these records from nearby weather stations illustrate the trend. 
Increased salinities accompany decreased precipitation. 
Our salinity records are few; on Transect C three measurements 
28 
