Overview

Monitoring rodent activity in the home cage provides valuable, unbiased insights into behavior. Because there is no intervention on the part of the researcher, the subjects can be monitored for longer time periods - even 24 hours per day over many weeks. And because subjects remain in their home cage, the behavior is not biased by exposure to a novel environment. Home cage monitoring is especially useful for studying circadian rhythms, toxicology, treatment effects, and for phenotyping genetically modified animals.

Tools

Specialized Cages

There are many commercially available options for specialized home cages that can monitor rodent activity over long durations. Some of these systems integrate additional data sources, such as food and water consumption, urine detection, and body mass. For researchers hoping to capture several data parameters over a long duration, these cages offer a comprehensive solution.

Pros

1. Multi-dimensional data
2. Long-term monitoring
3. Multiple subjects in parallel

Cons

1. Costly
2. Requires acclimatization, not 'true' home cage
3. Throughput ultimately limited by expense

Video-based monitoring

Video-based monitoring of home cage behavior can be accomplished with either single or multiple cameras positioned above or to the side of the cage. Video is a flexible medium because several kinds of downstream data can be extracted. General locomotor activity can be assessed or more complex behaviors, like rearing, grooming, and social interactions can be quantified.

Pros

1. Most detailed behavioral data
2. Relatively inexpensive
3. High-throughput

Cons

1. Difficult to implement with ventilated cage racks
2. Requires an IR-light source for nighttime
3. Algorithms may struggle tracking group-housed animals

IR Beam-based Monitoring

Infrared beam-break technology registers activity and position data. Systems mounted outside the home cage, like San Diego Instruments Photobeam Activity System, make it possible to keep animals in their own home cage without any disruption and check in on them remotely.

Pros

1. Non-invasive and high-throughput
2. Uses home cage for minimal disruption
3. Captures activity, rearing, and X,Y position

Cons

1. Not ideal for group-housed animals
2. Misses more granular behaviors, like drinking or grooming

Implanted telemetry and RFID

Implanted telemetry and RFID systems send position data to a receiver board placed under the home cage. Many telemetry products are capable of collecting additional data like body temperature and heart rate, but require a more invasive surgery to implant. RFID is typically minimally invasive, implanted subcutaneously, and collects only position data.

Pros

1. Good for group-housed animals
2. Compatible with home cage
3. May collect additional data parameters

Cons

1. More invasive
2. Requires recovery from implantation
3. More effort to get started

Conclusions

Home cage activity is a valuable source of information. When selecting the right tools to monitor home cage activity, just keep in mind the goals of your specific experiment. If you need precise position data from group-housed animals, RFID or implanted telemetry might be the best option. If you need a non-invasive solution with remote monitoring, then video or photobeam systems might work best. As always, feel free to reach out to us at BehaviorCloud for tips and technical advice. Happy testing!