O mouse, where art thou? The Mouse Position Surveillance System (MoPSS)—an RFID-based tracking system

Abstract

Existing methods for analysis of home cage-based preference tests are either time-consuming, not suitable for group management, expensive, and/or based on proprietary equipment that is not freely available. To correct this, we developed an automated system for group-housed mice based on radio frequency identification: the Mouse Position Surveillance System (MoPSS). The system uses an Arduino microcontroller with compatible components; it is affordable and easy to rebuild for every laboratory because it uses free and open-source software and open-source hardware with the RFID readers as the only proprietary component. The MoPSS was validated using female C57BL/6J mice and manual video comparison. It proved to be accurate even for fast-moving mice (up to 100% accuracy after logical reconstruction), and is already implemented in several studies in our laboratory. Here, we provide the complete construction description as well as the validation data and the results of an example experiment. This tracking system will allow group-based preference testing with individually identified mice to be carried out in a convenient manner. This facilitation of preference tests creates the foundation for better housing conditions from the animals’ perspective.

Rating enrichment items by group-housed laboratory mice in multiple binary choice tests using an RFID-based tracking system

“…Thereby we could demonstrate that group housed mice can explore a choice test apparatus without being directly led by others and thus an independent choice is likely. Nevertheless, testing groups of mice will remain a challenging issue with regard to choosing the correct statistical unit 31,35,36 . Especially during the inactive phase, the location of a shared nest might influence the choice of the group.…”

“…Mice are social animals in nature, and in accordance to underlying legislation 1 , single housing should be avoided under experimental conditions if possible. Furthermore, it is arguable whether choice decisions of individually kept animals can be transferred one-to-one to animals in a social group resembling realistic laboratory conditions 31 . Thus, we decided against testing individual animals and used the option of the home cage based choice experiment to study the mice as socially living animals within the group 37 .…”

“…After 43 weeks in the enriched housing condition, preference tests were conducted using the Mouse Positioning and Surveillance System (MoPSS) 31 . The system consisted of two macrolon type III cages, connected with a 30 cm plexiglas tube.…”

“…The mouse tag detections were automatically saved onto a microSD card during the experiment and each detection was marked by a current timestamp with the antenna number (left/right) and the individual mouse RFID tag number. Data analysis and sanity checks with logical correction of missing detections were done using a data evaluation script in the software R (R version 4.0.4, R Studio version 1.3.959) specially developed for MoPSS data analysis 31 . No missing data were found, all mice were regularly detected and none had to be excluded from analysis of stay times.…”

“…For our preference test, we used the Mouse Position Surveillance System (MoPSS), a new test system designed and constructed in our laboratory 31 to ask for enrichment item preferences in female C57BL/6J mice, a widely used strain in biomedical research 32 . The MoPSS allows automatic long-term calculation of time spent in each of two interconnected cages for every individual mouse in a group.…”