You may not think that a rat is worthy of its very own San Diego Zoo animal fact page, but the African giant pouched rat is no ordinary rodent! These animals are intelligent, energetic, friendly, and pretty cute…if you squint one eye. And they have a nose that knows.

About the size of a small domestic cat, these agile rodents have been trained to detect landmines and buried explosives left over from wars. They have worked in seven countries, including Cambodia, Angola, and Mozambique, securing areas so local people can live safely. Another humanitarian task the rats are trained for is detecting tuberculosis (TB) in samples collected in hospitals. TB is one of the world’s deadliest infectious diseases, and the detection rats hasten discovery of the disease for a fraction of the cost.

There are two species of African giant pouched rat: Cricetomys emini and C. gambianus. The latter is the working species used in landmine and TB detection, and the type that will be joining the San Diego Zoo’s new Sanford Children’s Zoo, opening in 2021.

Giant backstory: Twenty years ago, a Belgium fellow named Bart Weetjens founded the nonprofit organization APOPO, which harnesses the highly attuned sense of smell in the African giant pouched rat to make the world a better place. As a teenager, Bart had trained his own pet rats to find hidden objects for treats; and as an adult, he wondered if rats could be trained to find hidden explosives. After receiving a grant from the Belgium government, the APOPO project was born, and later expanded to include TB detection. His raring rodents became known as Hero Rats. According to their website, these rodents have helped clear over 106,000 landmines and identified over 12,000 TB-positive patients in Tanzania and Mozambique (a TB detection facility is being built in Ethiopia).

Given the Hero Rats' astonishing success rate and affordability, APOPO recently began a pilot program with the U.S. Fish and Wildlife Service to tackle wildlife trafficking in exotic hardwoods and one of the most exploited species on the planet: the pangolin. A group of Hero Rats recently began their rigorous training for this new mission in Tanzania. “This is a case where Mother Nature has built a detection system that, coupled with modern technology, can save lives in places where cost-effective and efficient tools aren’t readily accessible,” explained Bart. “Even after 20 years of working with them, I’m still in awe of what they can do.”

Working rats. One huge advantage to using African giant pouched rats for landmine detection is the speed at which they efficiently find actual explosives and ignore other debris like coins, nuts and bolts, and other scrap metal. One highly trained rat can check 2,200 square feet (200 square meters)—about the size of a tennis court—in about 20 minutes. It would take a technician with a minesweeper up to four days to clear the same amount of space.

Additionally, the rats are indigenous to sub-Saharan Africa, so they are well-adapted to heat and resistant to many tropical diseases. The rats are widely available and easy to procure, though not all will succeed at the rigorous training program. Weighing 2 to 3 pounds (1 to 1.4 kilograms) on average, the pouched rats are easy to transport, and they are light enough to not trigger the random explosives in field sites (a landmine requires at least 11 pounds (5 kilograms) of pressure to be activated). Long lived for a rodent, their six- to eight-year lifespan makes training a worthwhile investment. They are food motivated, and willing to work with just about any handler for a proper reward.

Tuberculosis is a highly contagious disease that can be fatal if left untreated. African giant pouched rats have been trained to detect TB by sniffing sputum samples. The rats can test hundreds of samples in a day, compared with about 40 getting tested in a day by traditional methods. Since 2002, the rats have screened 226,931 samples and identified 5,594 TB patients just in the Tanzanian city of Dar es Salaam. According to a Wall Street Journal report, by 2016, the Hero Rats “had identified 10,000 TB-positive patients whose infections went undetected by local clinics.”

Works for peanuts…and bananas. Convincing a three-pound rat to do your landmine detection bidding and do it correctly takes a bit of patience. The APOPO website explains the procedure: When the pouched rats are weaned, at around four weeks of age, they begin to socialize the animals to get them used to being handled and exposed to a variety of sights and sounds.

Positive reinforcement is used, and soon the rats learn to associate the sound of the clicker with a food reward (banana or a banana-peanut paste is their favorite). Training sessions last about 30 minutes, 5 days a week (they get weekends off to relax). They are trained to indicate which hole in a line contains TNT (an explosive) by nosing it for five seconds.

After “odor imprint,” the work gets more difficult. They are exposed to various scents before progressing to sandbox training, where the target scent is buried and the rat must walk in “lanes,” up and down systematically, to scout the entire area. Finally, the rat is trained to wear a harness and practice outdoors on a lead, finding inactive mines under the soil. At the end of the training, they are given a 2-day final exam: they must find all the mines in an area of 480 square yards (400 square meters) randomly spiked with inactive mines. Even the handlers do not know where the mines are located. The rats must score 100 percent on the test to become certified landmine-sniffing rats. When the professional rat is working an area, it scratches at the ground when an explosive is detected; the handlers mark the spot, and the landmine is safely removed later.

Fur and fanfare. An African giant pouched rat can reach three feet in length, with half of that consisting of a hairless tail. Unlike domestic rats, these giants have cheek pouches like hamsters, which they fill with nuts at night to store underground. It has been known to fill its pouches to capacity with date palm nuts to the point of barely being able to squeeze back into its burrow. It has a tawny, buff-gray, or mottled coat of coarse or sleek fur and a pale, cream-colored underside. Its ears are erect and nearly hairless. Long, twitching dark whiskers help it navigate the world. It is limber and lithe, and eager to please (for a treat).