The winter excess in vole catch correlation was sensitive to analysis choices in five Swedish areas, 2002–2025

Voles are a food source for many predators. We tested whether seasonal vole catch changes were more closely linked across five Swedish monitoring areas in winter than in summer. We used unchanged SLU count workbooks and 23 complete summer-winter pairs per area. Summer covers spring to autumn in 2002–2024. Winter covers those autumns to the next spring, through 2025. Mean Pearson correlation across ten area pairs was 0.284 in summer and 0.476 in winter. The difference was 0.191. A synchronized four-year block bootstrap gave a nominal 95% interval of 0.003 to 0.296. The interval included zero with two-year or three-year blocks, with rank correlations, after trend removal, and after adjustment for starting catch. Field vole alone gave a difference of 0.063, with an interval of -0.107 to 0.233. The observed winter excess was positive in all planned estimates, but its statistical support was sensitive to analysis choices. These catch records do not establish a general winter excess or its cause. The package contains five source workbooks, a balanced seasonal table, all 19 planned estimates, figures, bootstrap draws, provenance, code, and independent arithmetic and clean-run checks. Limits include five fixed areas, only about six population cycles, different species mixes, and no session-level effort or detection model.

vole · spatial synchrony · seasonal change · Sweden · long-term monitoring · block bootstrap · reproducible research