Factors driving California pocket mice (Chaetodipus californicus) population dynamics

Abstract

Understanding how demographic parameters respond to climatic variables is essential for predicting species response to changing environmental conditions. The California pocket mouse (Chaetodipus californicus) is an inhabitant of coastal-central California oak (Quercus spp.) woodland that is undergoing a rapid anthropogenic transformation while also facing effects of global climate change. We analyzed the population dynamics of the California pocket mouse by applying Pradel s temporal symmetry model to a 10-year (2004 – 2013) capture–mark–recapture data set to estimate survival and recruitment rates and realized population growth rate. The overall monthly apparent survival probability (ϕ) was 0.76 ± 0.01 SE and was slightly higher in the dry season (0.79 ± 0.02 SE) than the wet season (0.74 ± 0.01 SE). Coefficients of variation (CV) of temperature and rainfall (with and without a one-season lag), average seasonal temperature, and regional climatic variation (El Niño index) positively influenced ϕ. Overall monthly recruitment rate (f) was 0.17 ± 0.01 SE but varied seasonally; f was substantially higher during the dry season (0.39 ± 0.04 SE) than the wet season (0.09 ± 0.02 SE). Average seasonal temperature, CV of temperature and rainfall (without a one-season lag), and total seasonal rainfall (with a one-season lag) positively influenced recruitment, whereas regional climatic variation (El Niño index), total seasonal rainfall (without a one-season lag), and CV of rainfall (with a one-season lag) had a negative effect on f. Monthly realized population growth rate (λ) was 1.00 ± 0.02 SE for the entire study period, but it varied temporally. Our study provides the first estimates of demographic parameters for the California pocket mouse and tests for the influence of climatic variables on these parameters. Although the California pocket mouse population remained relatively stable during our study (as indicated by λ = 1.00), changing climate and anthropogenic influences on California oak woodland could adversely influence demographic parameters and population dynamics and might also indicate effects of climate change on its ecologically sensitive habitat.