In semi-arid environments, small mammal populations are typically driven by aperiodic rainfall pulses, which affect plant production and resulting resource availability for higher trophic levels, with strong bottom-up regulation. Using a 20-year biannual capture–recapture dataset (1993 to 2014), we investigated the population dynamics of the brush mouse (Peromyscus boylii) and examined the impacts of environmental factors on its demography in semi-arid, blue oak–coast live oak woodland of coastal–central California. We applied Pradel’s temporal symmetry models to estimate capture probability, apparent survival, and realized population growth rate of the brush mouse, and the effects of rainfall, temperature, and El Nino on these demographic parameters.
Results/Conclusions
The population was stable during the study period, with a monthly-realized population growth rate of 0.993 ± SE 0.002. However, growth varied over time from 0.680 ± 0.054 to 1.449 ± 0.083. Monthly survival averaged 0.802 ± 0.005, and also exhibited variation in time (from 0.530 ± 0.063 to 0.948 ± 0.030) and sex. Monthly recruitment averaged 0.175 ± 0.038, and varied from 0 to 0.539 ± 0.083. Survival and growth were positively correlated with rainfall, and negatively correlated with temperature. In contrast, recruitment was positively correlated with both temperature and rainfall in the current season, but negatively correlated with rainfall from one year ago. El Nino had no or a negligible effect on vital rates. Populations were maintained using a combination of coping strategies, primarily through high recruitment, although during periods of drought recruitment was negligible and survival was the primary driver of growth rate. Our results indicate that rainfall and temperature are both important drivers of brush mouse population dynamics, and will play a significant role in predicting the future viability of brush mouse in its highly variable and resource–restricted environment.