We have been operating in TB and demining for long enough now that some of our rats have reached retirement age, which is typically between 7 and 8 years of age. We allow them to work as long as they are performing well, still feel like working and pass weekly health checks. We notice that the rats are generally enthusiastic to get to work but when they are growing old, some simply don’t feel like getting out of their cage to work anymore. If that happens or when a rat’s performance has declined or it is not healthy enough to continue working, the rat is retired to its home cage. When they are retired to their cages, they receive a healthy diet, are regularly taken out to play and exercise, and continue to receive weekly health checks. If a rat is clearly suffering in its old age or from an untreatable disease, it is humanely euthanized.