Giant rats have been trained to sniff out unexploded landmines in Africa, and they are now also being used in Cambodia. There are nearly 3,000 landmine accidents every year around the world; nearly half of them involving children.

Rats sniff landmines
A trained rat attempts to sniff out explosives in a fieldXavier Rossi

In countries such as Cambodia and Angola, vast tracts of land have been rendered off-limits for decades, yet only about 3% of that land typically contains any explosive material. The rest sits idle, as communities are too afraid to use it.

 This is when the rats step in where others fear to tread.

A trained rat can cover much more land than a human with a metal detector. The rats' superior sense of smell means that in just 20 minutes, they can do what it would take a human mine detector up to four days to do. A human deminer has to stop every time the metal detector gives a signal, but often it turns out to be an old coin or piece of scrap metal. The rat only detects explosive (TNT) so ignores all the scrap metal and goes straight to the landmine.

They are much cheaper than human workers – when the rats detect explosives, they are rewarded with a piece of fruit. Using the rodents is far less dangerous, too, as although they are giant rats, they are too small to set off landmine detonators.

Gambian pouched rats, also known as African giant pouched rats, can grow up to 1m (3ft) long and weigh 1.4kg.

Rats sniff landmines
An Apopo handler poses with a mine-detecting rat in AngolaApopo
Rats sniff landmines
Workers use a metal detector in AngolaApopo
Rats sniff landmines
A rat sniffs out unexploded landmines in AngolaApopo
Rats sniff landmines
Apopo handlers prepare for a day's work with their ratsApopo
Rats sniff landmines
A mine-finding rat waits to be put to workApopo
Rats sniff landmines
A trained rat sits on a handler's shoulderApopo
Rats sniff landmines
A handler and a rat look at unexploded landmines found in MozambiqueXavier Rossi

The project is the brainchild of Bart Weetjens, founder of Apopo (A Flemish acronym of Anti-Persoonsmijnen Ontmijnende Product Ontwikkeling, or Anti-Personnel Landmines Detection Product Development in English). The Belgian non-governmental organisation began breeding giant rats in 1997 and soon found they could detect not just landmines but tuberculosis in humans, too.

The rats have been used extensively in war-torn areas of Africa. Plagued by 27 years of civil war, Angola is the third-most mine affected country in the world after Afghanistan and Cambodia, according to the Landmine Monitor. The rats are helping to clear landmines and other unexploded ordnance from fields, returning land to local communities.

Rats sniff landmines
A map shows the location of landmines in a field in AngolaApopo
Rats sniff landmines
A man who lost his leg to a landmine plays with a trained ratApopo
Rats sniff landmines
Two handlers put a leash on a trained rat in AngolaApopo

In April 2015, Cambodia received 15 rats, which went to work in areas densely mined during the second Indochina war. During 2015 the teams managed to remove 1,345 landmines and destroy 13,594 items of unexploded ordnance. As many as three million mines are estimated to be scattered across Cambodia, left over from 30 years of conflict that started in the 1960s. In addition, at least 26 million bombs were dropped on Cambodia during the Vietnam War, many of which remain active.

Around 20,000 Cambodians have been killed by unexploded ordnance since 1979, with 154 killed or injured in 2014.

Rats sniff landmines
A trained rat searches for landmines in CambodiaBriana Marie
Rats sniff landmines
Mine-detecting rats are seen near a sign warning of unexploded ordnance in CambodiaBriana Marie
Rats sniff landmines
A Cambodian Mine Action Centre (CMAC) handler with a trained ratBriana Marie
Rats sniff landmines
Landmines found in CambodiaBriana Marie
Rats sniff landmines
Seany Oeurn, age 68, from Cambodia: 'I was 42 years old when I was injured by a landmine. I was a spy against the Khmer Rouge and was fooled by a suspicious looking pile of bamboo. I thought it was a trap and walked around it but they had laid a landmine in my path. During the war I lost all my seven cattle, four water buffalo and my leg to landmines, bombs and guns. I lost friends as well. They took everything, including my dignity. I am a widower and it is difficult knowing that my family must take care of me. I am still in pain at the end of my leg. But I have so much gratitude for the work APOPO and CMAC are doing for us. My four daughters and grandchildren live with me and my oldest daughter was shocked to hear that the landmines are still present in the field where I was injured. She believed that once the landmines are old then they become inactive. We were even more surprised when APOPO and CMAC found two active mines there the previous week. Now my family are finally safe'Briana Marie
Rats sniff landmines
Mr Moch Ban, 50 years old, from Cambodia: 'In 2002 I went into the forest to cut wood to cook food and heat our home. I stepped on a mine and I lost my left leg below the knee. Today our life is hard. Without a leg it is complicated to grow rice. We are worried about our children too. There are still many mines in the forests close to here'Matthias Canapi

Every year on 4 April, the United Nations aims to raise awareness of the plight of communities living in daily fear of landmines through its International Day of Mine Awareness and Assistance in Mine Action.