Small-mammal abundance in year t-1 did not predict blacklegged tick nymph counts in year t at six NEON forest sites (2014-2024); same-year mammal abundance had a negative association

Question: at one New York site, white-footed mouse density in year t-1 predicts the density of host-seeking blacklegged tick (Ixodes scapularis) nymphs in year t. Does this lag rule apply at the US National Ecological Observatory Network (NEON) sites, where ticks and small mammals are sampled with standard methods? Approach: NEON RELEASE-2026 drag-cloth tick counts, small-mammal box trapping and tick pathogen tests (neonDivData tables). Negative binomial models of site-year tick counts with dragged-area offset, site fixed effects and the log2 small-mammal index of years t-2, t-1, t and t+1 (placebo); within-site permutation tests; year effects, other host indices and windows, leave-one-site-out and leave-one-year-out fits. Lone star tick (Amblyomma americanum) nymphs were a control species. Results: at six eastern forest sites (56 site-years), a doubling of the Peromyscus index in year t-1 changed nymph counts by a factor of 1.02 (95% CI 0.85-1.23; permutation p = 0.84; 0.85, 0.70-1.03 with year effects). The 80% minimum detectable factor was 1.31. Nymph counts had a negative association with the same-year index: 0.69 (0.59-0.81; p < 0.001), stable at 0.62-0.76 in all robustness fits. Dermacentor variabilis adults showed a similar same-year association (0.69; p = 0.028); A. americanum nymphs did not (0.85; p = 0.22). The same-year association came from mammals trapped in August-October, after the nymph peak, not from mammals trapped during questing. Thus simple host removal of questing nymphs does not explain it fully, and a shared year-level cause is possible. Borrelia burgdorferi s.l. prevalence in 4,068 tested nymphs (8 sites, 48 site-years) did not change with Peromyscus abundance, P. leucopus share or small-mammal richness in year t-1 or t (all p >= 0.24), so we found no dilution signal. Limitations: few sites and about ten years per site; tick and mammal plots are 300-830 m apart; no deer, bird, acorn or weather data; statistical association only.

Ixodes scapularis · Lyme disease · Peromyscus · NEON · tick density · small mammals · time lag · dilution effect · Borrelia burgdorferi · Amblyomma americanum · Dermacentor variabilis · negative binomial · permutation test · forecasting