. The ecology of delta marshes of coastal Louisiana : a community profile. Marsh ecology -- Louisiana; Wetlands -- Louisiana. 1920 1945 Figure 58. Annual muskrat harvest from a 52,200-hd brackish Scirpus ojneyi marsh in the Mississippi Delta (O'Neil 1949). kill much vegetation digging for the preferred roots. In addition, their house-building activity, underground runs, and surface trails (Figure 59) destroy much more marsh than is directly eaten. For example, in a ID-ha brackish marsh area that contained 24 active and 30 inactive houses in April 19S2, 31 new houses were built and 10 "ref
. The ecology of delta marshes of coastal Louisiana : a community profile. Marsh ecology -- Louisiana; Wetlands -- Louisiana. 1920 1945 Figure 58. Annual muskrat harvest from a 52,200-hd brackish Scirpus ojneyi marsh in the Mississippi Delta (O'Neil 1949). kill much vegetation digging for the preferred roots. In addition, their house-building activity, underground runs, and surface trails (Figure 59) destroy much more marsh than is directly eaten. For example, in a ID-ha brackish marsh area that contained 24 active and 30 inactive houses in April 19S2, 31 new houses were built and 10 "refurbished" during the next year (Table 23). Sixty percent of the active houses and 57 percent of the inactive ones simply disappeared. When muskrat populations are dense, all this activity can decimate a marsh, creating large "eat-outs" especially in the favored brackish marsh three-corner grass (Sci rpus olneyi) (Figure 60). Subsequently the local population, with no. Figure 59. Ground plan of a typical muskrat house with underground runways and surface trails (barred lines) (Arthur 1931). food, crashes. If water levels are low for a year or two to allow regrowth of the vegetation, the marsh may recover (and the muskrat population with it), but often the damage extends so deeply into the marsh that recovery is poor at best. Severe storms may reset this cycle by destroying nests and burrows and drowning the predatory disease organisms they harbor. The muskrat population often comes back strongly after these storms (O'Neill 1949). It is interesting that "eat-outs" are seldan found outside of brackish marshes and are always attributed to muskrats, not nutria (O'Neil 1949). The nutria has a much longer gestation period (130 days compared to 28 days for the muskrat) so that its potential for response to environmental change is much slower than the muskrat's. Consequently, its population is more stable. Muskrat "eat-outs" in fresh marshes have been
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