Small Mammal Community Response to Wildfire at the Altona Flat Rock Sandstone Pavement Barren

Abstract

The Altona Flat Rock is a sandstone pavement barren, dominated by the fire-dependent species known as Pinus banksiana (Jack Pine). Changes in seed availability, understory structure, and predator presence influence wildlife migration within the barren. Additionally, small mammal abundance often fluctuates cyclical in response to tree masting. In July 2018, a wildfire occurred at the Flat Rock pine barren. We aimed to monitor small mammal response to wildfire over the course of a year. Small mammal traps were set along established transects capturing the fire severity gradient and adjacent reference unburned area. Along those same transects, giving up density surveys (GUDS) were performed to foraging patterns in these varied microhabitats. We predicted greater capture rates and community diversity in the burn immediately post-fire due to access to the abundant serotinous Jack Pine seeds. In fall 2018 immediately following the wildfire, a total of 67 small mammals were captured with 1.5 times more in the unburned than burned area. The small mammal community consisted of Peromyscus spp. comprising 87% of captures and insectivores Sorex cinereus (Masked Shrew) and Blarina brevicauda (Northern Short-tailed Shrew) were absent from the burn. In fall of 2019, a total of 21 small mammals were captured with 3 times more in the burn than in unburned area. Community composition was exclusively Peromyscus spp. Over the course of a year, we noted a significant reduction in captures and a shift in microhabitat usage from unburned (2018) to burn (2019) likely in response to regenerating vegetation ameliorating predation risk. Interestingly, average body mass and total body length were higher in Peromyscus spp. in 2019, perhaps in response to increased seed predation. GUD survey results show seed foraging was 67% greater in 2018. Collaborators monitoring game cameras at the barren noted increased predator use of the unburned and burned areas in winter 2018 and spring 2019, respectively and a significant decline of predators from the area in late summer-fall 2019. A predator decrease in fall 2019 is paralleled with a significant decline in Peromyscus spp. This preliminary research has revealed the complexity of small mammal response to wildfire. Long-term monitoring will likely uncover their connection to resources, microhabitat structure, and predator abundance as regeneration continues.