Mice population dynamics and structure over time and space after wildfires

Abstract

Rodents respond quickly to changes in habitat structure after wildfires. They constitute important prey items for vertebrate predators and influence vegetation structure and regeneration. Assessing the population dynamics of rodents in burnt areas, whether individuals originate from in situ survival or from ex situ immigration, is therefore a key question in understanding the recovery of trophic networks after disturbance. This study aimed to identify the recovery strategies of rodent populations in recently burnt forests in the Mediterranean basin using body condition, reproductive output, sex ratios, and distance covered by wood mice and Algerian mice. Sampling stations were set up at increasing distances from the perimeter of recently burnt areas. Rodents were captured using Sherman traps and measured. Wood mice and Algerian mice lived syntopically within the recently burnt areas studied, the former species being more abundant and the second one selecting drier areas. Results indicated that time since fire, shrub cover, and distance to the perimeter of the burnt area influenced wood mice and Algerian mice population structures. Adult female wood mice mainly remained close to the burnt area perimeter, due to this species' matriarchal structure, while juvenile males dispersed farther into the burnt area. Adult females were also recaptured more frequently than other age and sex categories over time, whereas males covered greater distances. These findings suggest that the recovery strategy of these widespread Mediterranean rodents is mainly driven by ex situ immigration from unburnt areas. These results will be useful for post-fire management decisions such as non-intervention, salvage logging or the conservation of open areas, given that mice are a fundamental component of the ecosystem. Results also suggest that management should focus on maintaining good connectivity between burnt and adjacent unburnt areas to support mice populations and facilitate other longer-term conservation benefits.