Oryzomys

The massive decline in mammal populations in Everglades National Park (ENP) has likely disrupted the fragile ecosystem unique to South Florida. Mammals populations in the park are a mere fraction of what they have been historically. However, very few studies have investigated some of the smaller mammals which are still widely present. Mark-recapture trapping was used over 4.5 years on tree islands in ENP to analyze the communities of three focal species: the hispid cotton rat (Sigmodon hispidus), marsh rice rat (Oryzomys palustris), and cotton mouse (Peromyscus gossypinus). We assessed the reproduction, effect of water levels and seasonality, and density of all three species over time. There was no significant association between water levels and reproductive activity for the cotton mouse or cotton rat, while the rice rat showed more reproductive adults during periods of standing water. The overall densities of all three species were higher in times of dry ground versus when the landscape was inundated. Average and maximum density estimates yielded higher numbers of rodents than observed in ENP.