Prescribed fire effects on grassland small mammal community structure in eastern North Dakota

Background/Question/Methods

Grassland small mammal communities are presumed to change composition following fire, primarily in response to changes in vegetation structure and cover. Immediately after fire, species that prefer open areas (e.g., Peromyscus maniculatus [deer mice]) are often more abundant than those that prefer greater litter depth (e.g., Microtus pennsylvanicus [meadow voles]). In consecutive growing seasons after fire, small mammal communities shift as litter and cover accumulate. We asked how fire related vegetation changes alter small mammal communities in a 383 ha native grassland site in Eastern North Dakota, USA. The site was divided into seven 40–60 ha management units in 2014 and each was treated with prescribed fire at different intervals. To collect small mammals, we set 8 snap traps at 90 total points (10–18 points per unit) for five consecutive nights mid-summer 2018–2020.

Results/Conclusions

Over the entire study period, we captured 10 species on the site, including two North Dakota species of conservation priority: Sorex hoyi (pygmy shrew) and Sorex arcticus (Arctic shrew). A majority (75%) of all captures were meadow voles. Small mammal composition varied among units where recently burned units were distinct from units burned two, three, or four years prior. In 2018, M. pennsylvanicus and P. maniculatus were positively and negatively related to litter depth, respectively. Contrary to previous studies, M. pennsylvanicus were most numerous in the most recently burned unit in 2019. As hypothesized, P. maniculatus was high the first year after fire and declined the second year. Sorex sp. populations appeared to have a delayed fire positive response with higher numbers two years after fire. These findings suggest that small mammal responses to fire are temporally dynamic and are more regionally specific than originally hypothesized.