Modelling Deroceras reticulatum (Gastropoda) population dynamics based on daily temperature and rainfall

A simple mathematical model was developed, using ordinary differential equations, to understand the dynamics of Deroceras reticulatum populations. Field data from a long term experiment were interpolated to give daily data for the numbers of slugs m−2. Using a model calibration procedure, rates estimated from interpolated data were found to be different from the laboratory rates used to initialise the model. The calibrated model explained 81.2% of the total variation in the interpolated data. Calibration results indicated that rainfall and temperature influenced each rate and affected adults and juveniles differently. Juvenile mortality appeared to be only affected by temperature, whilst the juvenile recruitment rate and the rate of adult mortality were found to be more dependent upon rainfall. The model was then simulated over a three and a half year period for comparison with the interpolated data for the same period. Qualitative changes in the interpolated slug abundance were well described by the model. The results suggest that with a better understanding of between year and site factors, and the inclusion of time delays and egg laying, this model could provide a more accurate forecast of slug abundance.