Magawa the rat, who was awarded a gold medal for his heroism, is retiring from his job detecting landmines.
In a five-year career, the rodent sniffed out 71 landmines and dozens more unexploded items in Cambodia.
But his handler Malen says the seven-year-old African giant pouched rat is "slowing down" as he reaches old age, and she wants to "respect his needs".
There are thought to be up to six million landmines in the South East Asian country.
Magawa was trained by the Belgium-registered charity Apopo, which is based in Tanzania and has been raising the animals - known as HeroRATs - to detect landmines since the 1990s. The animals are certified after a year of training.
Last week, Apopo said a new batch of young rats had been assessed by the Cambodian Mine Action Centre (CMAC) and passed "with flying colours".
Magawa, the group said, would stay in post for a few more weeks to "mentor" the new recruits and help them settle in.
"Magawa's performance has been unbeaten, and I have been proud to work side-by-side with him," Malen said.
"He is small but he has helped save many lives allowing us to return much-needed safe land back to our people as quickly and cost-effectively as possible."
Last September, Magawa was awarded the PDSA Gold Medal - sometimes described as the George Cross for animals - for his "life-saving devotion to duty". He was the first rat to be given the medal in the charity's 77-year history.
He weighs 1.2kg (2.6lb) and is 70cm (28in) long. While that is far larger than many other rat species, Magawa is still small enough and light enough that he does not trigger mines if he walks over them.
The rats are trained to detect a chemical compound within the explosives, meaning they ignore scrap metal and can search for mines more quickly. Once they find an explosive, they scratch the top to alert their human co-workers.
Magawa is capable of searching a field the size of a tennis court in just 20 minutes - something Apopo says would take a person with a metal detector between one and four days.