Small Mammal Response to Prescribed Fire in the Coastal Sand Plain Ecoregion

Abstract

Prescribed fire is a common method for managing forests and rangelands for livestock and wildlife in the United States. In areas like the Coastal Sand Plain ecoregion of Texas, prescribed fire is used to remove mature gulf cordgrass (Spartina spartinae) and create early successional conditions that provide greater nutritional value for livestock. The long-term benefits of these fires for large herbivores have been shown, but the effects on small mammals that use this vegetation for food and shelter are largely understudied. The goal of my project was to determine how small mammal communities recover from fire in Coastal Sand Plain ecosystems. Small mammal species (i.e., mouse and rat species) can be used as indicators for ecosystem health, functioning, and overall biodiversity. I conducted a long-term monitoring study on the East Foundation’s El Sauz Ranch, where an established prescribed fire impact study was taking place. From 2019 to 2022, I monitored unburned (i.e., control) and burned (i.e., treatment) areas; treatment areas were burned at varying intervals (every 3 or 5-7 years) during winter. I used Sherman live traps to capture small mammals, which were uniquely tagged, and capture-mark-recapture methods to estimate abundance and species richness within burned and unburned plots. The average total abundance of small mammals at 5-weeks post-fire (108.69 ± 16.87 individuals/200m2) was significantly lower (t=–4.224, df=8.662, P=0.002) than the control average (287.48 ± 26.19 individuals/200m2 ), but at 1-year post-fire, abundance was similar to control treatments (199.71 ± 25.33; t=–0.934, df=9.237, P=0.374). However, species richness ranged from 4 to 6 species on average by treatment. After observing an increase in total small mammal abundance starting 1 year after prescribed fire, and acknowledging that small mammal abundance was not different than the control average for plots sampled 2 years after fire (314.33 ± 39.67 individuals/200m2 ; t=1.393, df=10.629, P=0.192) and 3 years after fire (231.38 individuals/200m2 ± 30.97; t=–1.176, df=19.854, P=0.253), I recommend a prescribed fire frequency of approximately 2 years for this ecoregion. This fire return interval will be beneficial for livestock grazing and lead to favorable ecosystem conditions for many wildlife species, particularly small mammal communities.