Silver Rice rat

Oryzomys palustris natator

Overall vulnerability:

Moderate to High
lower vulnerability
higher vulnerability

Conservation status:

Federally Endangered

General Information

The silver rice rat is a subspecies of the rice rat endemic to the Lower Keys in Florida. Rice rats are primarily nocturnal and will spend their evening hours foraging for mangrove seeds, coconut palm and isopods along with other plant and animal matter. Peak reproduction for this species occurs during the dry season, beginning in October. This species is thought to have a lower reproductive rate than many other small rodents.

Habitat Requirements

The silver rice rat is semi-aquatic and restricted to a small range of wetland habitat types found in the Lower Florida Keys. Low salt marsh and mangrove habitats support this species and rice rats have also been known to use freshwater marsh habitat in the Keys.


Habitat area:

  • 4,968 hectares within Florida (modeled)
  • 4,083 hectares (82%) is located on public lands

Habitat impacted by up to 3 meters sea level rise:

100%1 meter100%3 meters0%not impacted

Climate Impacts

This endemic subspecies is currently threatened by habitat loss and degradation and predation by feral cats. These existing threats coupled with extremely high vulnerability to sea level rise, make it likely that the silver rice rat will be significantly impacted by climate change. Additionally, this species is restricted from migration due to the geographic barriers of its island home and its genetic similarity to the mainland species of rice rat. If silver rice rats expanded beyond their limited range, they would likely be genetically swamped by similar mainland rats.

More information about general climate impacts to species in Florida.

Vulnerability Assessment(s)

The overall vulnerability level was based on the following assessment(s):

  • Standardized Index of Vulnerability and Value Assessment

    Vulnerability: Highly vulnerable

    The primary factors contributing to vulnerability of the rice rat are sea level rise, presence of barriers, minimal habitat protection, habitat fragmentation, changes in salinity, runoff and storm surge, and alterations to biotic interactions.

Adaptation Strategies

  • Conservation of existing habitat will allow the silver rice rat the best chance of recovering and maintaining a healthy population as climate change begins to accelerate.
  • As sea level rise may eventually become too great a threat for the silver rice rat in its current habitat and range, developing and maintaining a captive breeding population and assisted migration to a new location absent of similar rice rats are strategies to consider for this species.
  • Controlling existing threats such as feral cats is an important first-step in increasing rice rat population resilience and ability to adapt.

More information about adaptation strategies.

Additional Resources