Stark differences across flood risk zones in the Mississippi River floodplain landscape are revealed by an occupancy survey of Missouri swamp rabbits (Sylvilagus aquaticus)

Abstract

Context. Flood protection zones in the Lower Mississippi Alluvial Valley, the often-inundated unprotected side or “batture” and the intermittently flooded protected side, are a juxtaposition of sharply different landscapes and ecological conditions. Swamp rabbits (Sylvilagus aquaticus), an indicator species for bottomland hardwood forests, inhabit both zones in the southeastern USA. Though the batture side of the levee offers more habitat and better-connected patches, increased flood severity (frequency and duration) due to climate change or other factors may displace swamp rabbits and other terrestrial vertebrates potentially making the area less habitable. Objectives. We used a habitat model to delineate swamp rabbit habitat patches in the flood zones and conducted occupancy surveys of the patches to determine whether swamp rabbits benefited from conditions on the batture side, despite the flood risk. Methods. The presence of swamp rabbits in habitat patches of southeastern Missouri, USA was ascertained through the observation of latrine logs. Swamp rabbit habitat patches were identified using species distribution modeling and a subset were further characterized using Q1 LiDAR. We evaluated detection and occupancy models which included patch and detection covariates to determine differences across flood risk zones. Results. Patch occupancy was high and similar across zones but detection probability was much higher on the batture side. Forest structure in habitat patches was not drastically different among patches on the protected and unprotected sides of the levee. The higher detection rate may have resulted from greater abundance driven by lower patch isolation. Conclusions. Levees that disconnect rivers from the floodplains have a profound effect on landscapes. Swamp rabbits can thrive in the landscape and habitat of the unprotected floodplain, despite their increased exposure to frequent flooding.