• Elias, Susan P.
  Holt Research Forest, University of Maine, Arrowsic, Maine
  
• Witham, Jack W.
  Holt Research Forest, University of Maine, Arrowsic, Maine
  
• Hunter Jr., Malcolm L.
  Department of Wildlife Ecology, University of Maine, Orono, Maine
  

Summer abundance of white-footed mice (Peromyscus leucopus) fluctuated periodically during 20 years (1983-2002) at the Holt Research Forest, Maine, USA, a pine-oak forest within 125 km of the northern edge of this species range. The oscillation period of the series was 4.0 years, with fluctuations greater that in P. leucopus populations in Indiana, Virginia, Ohio, and Pennsylvania. Abundance always increased after low population phase coupled with a large acorn (Quercus) crop, but in 3 summers population declines followed population peaks despite large acorn crops. We used linear autoregression to identify periodically after accounting for the relationship between mice and acorn mast. Among 3 candidate models, a 2nd-order lagged abundance (AR[2]) model fits the data better and had greater predictive value (total r squared = 0.69) than either a 1st-order (AR[1]) or an acorns-only model. The AR(2) term could represent unknown limiting factors, such as response of predators.