Survival and habitat use of sympatric lagomorphs in bottomland hardwood forests

Lagomorphs are important consumers and prey in ecosystems worldwide, but have declined due to land use changes and habitat loss, and such losses may be exacerbated for specialist species. We compared survival and habitat use of two closely related lagomorphs, the swamp rabbit (Sylvilagus aquaticus (Bachman, 1837)), a bottomland hardwood (BLH) forest specialist, and the eastern cottontail (Sylvilagus floridanus (J. A. Allen, 1890)), a habitat generalist. We tested whether survival and habitat use differed between radio-collared swamp rabbits (n = 129) and eastern cottontails (n = 72) monitored during December 2009 – December 2013 in southern Illinois. We found interactive effects of species and season on survival rates: swamp rabbits had higher annual survival (0.37 ± 0.05 (estimate ± SE)) than did cottontails (0.20 ± 0.05), but this difference occurred primarily during the growing season. Swamp rabbits were located closer to watercourses in areas characterized by higher basal area and more mature BLH forest cover compared with eastern cottontails. Our results suggest that BLH forests may be marginal habitat for cottontails and indicate predation as the primary cause of mortality for both species. Swamp rabbits use of early-successional BLH forest suggests that restoration efforts have been successful. However, as specialists, swamp rabbits remain restricted to a narrow band of bottomlands near watercourses and may benefit from improved upland cover that serves as refugia from flooding.

A landscape genetic analysis of swamp rabbits (Sylvilagus aquaticus) suggests forest canopy cover enhances gene flow in an agricultural matrix

Habitat loss and fragmentation pose a continued and immediate threat to wildlife and create a persistent need for ecological information at the landscape scale to guide conservation efforts. Landscape features influence population connectivity for many species and genetic analyses can be employed to determine which of these features are most important. Because population connectivity through dispersal is important to the persistence of swamp rabbits (Sylvilagus aquaticus (Bachman, 1837)) at the northern edge of their range, we used a landscape genetic approach to relate gene flow to landscape features that may impact dispersal success. We tested resistance values for attributes of land cover, watercourse corridors, canopy cover, and roads and used causal modeling and redundancy analysis to relate these representations of landscapes to genetic distance for swamp rabbits in southern Illinois, USA. Models that included canopy cover had the strongest correlations with genetic distance and were supported by our methods whereas other models were not. We concluded that high tree canopy cover enhances gene flow and landscape connectivity for swamp rabbits in southern Illinois. Our study provides important empirical evidence that landscape variables may impact the habitat connectivity of swamp rabbits. Preserving dispersal routes for swamp rabbits should focus on improving canopy cover, in both bottomland and upland, to connect suitable habitat.