A team of international scientists and risk assessment experts has developed a foundational blueprint for an innovative population model, designed to improve environmental safety testing for agricultural pesticides. The tool, named APODEMUS (A POpulation Dynamical spatially Explicit Model of the wood moUSe), was recently published as a “Formal Model” – a novel article type, in the Agricultural and Environmental Modelling journal.
Bridging the Gap Between the Lab and the Field
Currently, environmental risk assessments rely heavily on laboratory toxicity tests (often using Norway rats instead of wild mice) and field studies. While field studies are realistic, they are highly expensive, time-consuming, and are often limited to a few specific locations, crops, and weather conditions.
The wood mouse (Apodemus sylvaticus) is extremely common across Europe and lives in a wide variety of habitats, including farmlands. Because they eat a broad diet of seeds, plants, and insects, they frequently forage in agricultural fields. Consequently, the European Union uses the wood mouse as a primary “focal species” to evaluate whether a plant protection product (pesticide) poses an unacceptable risk to small mammals.
APODEMUS acts as a virtual testing ground
By creating a population model, scientists can simulate complex, real-world agricultural landscapes and farming scenarios to predict how pesticide exposure impacts animal survival and reproduction over the long term.
How does it work?
Overview diagram of the conceptual population model for APODEMUS. The model simulates the wood mouse life cycle, growth and reproduction. Landscape composition is captured by habitat types (numbers) and influences the space use of the simulated wood mice. Exposures can be linked to the use of defined habitat patches and types. Credit to Singer et al., 2026.
Published as a Formal Model (a new peer-reviewed publishing format designed to make modelling research FAIR (Findable, Accessible, Interoperable, and Reusable) by enabling scholarly credit for diverse research outputs and enhance the transparency and rigor of complex ecological and systems modelling). The current study focuses on the “conceptual model“, meaning the researchers have defined the biological and ecological rules the computer program will follow, essentially building a highly realistic “virtual wood mouse” before adding the complexities of exposure and effects of Plant Protection Products (PPPs) such as pesticides.
What differentiates APODEMUS from previous models is the explicit implementation of “Dynamic Energy Budget” that tracks how individual mice convert consumed food into energy for growth, body maintenance, and reproduction. These virtual mice are placed into realistic, grid-based landscapes (like woods, pastures, and crop fields) where they dynamically establish home ranges based on habitat attractiveness, with female territoriality naturally preventing overpopulation. Finally, the model simulates diet-based exposure by correlating the time a mouse spends foraging in specific fields to its food intake, which will be used in future updates to calculate exact pesticide ingestion.
Built on Massive Data and Unprecedented Collaboration
To ensure the simulation is scientifically rigorous and acceptable to government regulators, a massive foundation of real-world data was used. The authors conducted a systematic review of 341 scientific publications, extracting 1,295 specific data points about wood mouse biology.
A key highlight of this study is that the model was built through a collaboration with stakeholders – including ecological experts, risk assessors, and chemical regulators – in a dedicated workshop. By following a European standard for ecological modeling such as the European Food Safety Authority (EFSA) and “Pop-GUIDE,” they ensured that every decision in the model’s design is highly transparent and justified.
What happens next?
The researchers are currently translating this conceptual blueprint into functioning computer code. Once the virtual wood mouse population is up and running, scientists will introduce virtual pesticide applications into the model. This will allow them to evaluate how individual mice absorb toxins, whether they survive, and whether the overall population can recover under various real-world farming scenarios.
Ultimately, APODEMUS offers an innovative foundational blueprint and a practical tool aimed at helping regulators accurately test the environmental safety of agricultural pesticides by simulating their long-term effects on wild animal populations across a variety of realistic landscapes that would be otherwise impossible to assess through physical field studies
Original study:
Singer A, Schmolke A, Becher MA, von Blanckenhagen F, van den Brink N, Grimm T, Ibrahim L, Imholt C, Jacob J, Jakoby O, Laucht S, Løvik AN, Martin T, Muñoz CC, Preuss TG, Galic N (2026) Concept for APODEMUS – a wood mouse population model for pesticide risk assessment. Food and Ecological Systems Modelling Journal 7: e175714. https://doi.org/10.3897/fmj.7.175714
