Finding a stick nest in a forest: Habitat preference of the endangered Key Largo woodrat (Neotoma floridana smalli)

Background/Question/Methods

Habitat selection is important for understanding the distribution, abundance, and diversity of species, and can help identify key resources for the conservation of endangered species. Key Largo woodrats (Neotoma floridana smalli) are an endangered subspecies threatened by reduced habitat and non-native predators. Though their remaining tropical hardwood hammock habitat has been protected by government agencies, urbanization of the island prevents expansion. However, if we improve the quality of existing habitat, then it might support a larger woodrat population. To achieve this, we must first determine if woodrats prefer a particular habitat. Past studies on Key Largo indicated conflicting preferences for certain forest ages, and were based on live-trapping. Woodrats are known for building stick nests for shelters, food storage, and nurseries. Nest distribution has been shown in other woodrat species to indicate habitat preferences, and occupancy surveys can confirm current use. Therefore we asked if nest distribution and nest occupancy is related to forest age, nest substrate, proximity to abandoned roads, or fine-scale forest structure, expecting that they’ll be associated with one forest age, artificial substrate, and abandoned roads. Using variable-width line transect surveys, we mapped nests to assess distribution, then used remote cameras to determine occupancy rates.

Results/Conclusions

The nest distribution results show that woodrats have a strong preference for artificial substrate nests (using man-made materials) and for nests along abandoned roads. Though artificial substrate is more prevalent along abandoned roads, natural nests are also common. In comparison, nests did not seem to be more abundant in a particular forest age. The occupancy survey data support similar trends of preference, showing higher occupancy rates at artificial nests and abandoned road nests. The occupancy rates across forest ages again displayed no apparent preference. Key Largo woodrats appear to be attracted to artifacts of human disturbance. These results imply that woodrats perceive certain advantages from artificial and abandoned road nests, but may also be subject to hidden disadvantages. Perhaps woodrats see artificial substrate nests as more defensible, more spacious, or more easily maintained. But if woodrats truly prefer abandoned roads, they may also be exposed to the higher predation risk of edge areas. And if woodrats are attracted to artificial substrate, and to supplemental nests built of this substrate, then it is possible they may become dependent on artificial materials. These preferences have consequences on woodrat conservation, suggesting that woodrats may need continued human involvement in the long-term.