Forest officials rescue a female leopard from a dry well after tranquilising it, at a residential area in Guwahati, India, December 13, 2017. REUTERS/Anuwar Hazarika TPX IMAGES OF THE DAY 

Forest officials rescue a female leopard from a dry well after tranquilising it, at a residential area in Guwahati, India, December 13, 2017. REUTERS/Anuwar Hazarika 

A veterinary doctor covers a tranquilised Przewalski's horse from a sun at the acclimatisation enclosure in the village of Dolni Dobrejov near the city of Tabor, Czech Republic, June 18, 2017. Picture taken June 18, 2017. REUTERS/David W Cerny 

A veterinary doctor holds a tranquilised Przewalski's horse at the acclimatisation enclosure in the village of Dolni Dobrejov near the city of Tabor, Czech Republic, June 18, 2017. Picture taken June 18, 2017. REUTERS/David W Cerny 

Kenya Wildlife Services veterinarians take blood samples of a tranquilised 5-year-old lioness named Nyala as they set up a radio collar on her neck to track her pride's movements at the Nairobi National Park near Nairobi, Kenya January 23, 2017. REUTERS/Thomas Mukoya 

Kenya Wildlife Services veterinarians set up a radio collar on the neck of a tranquilised 5-year-old lioness named Nyala to track her pride's movements at the Nairobi National Park near Nairobi, Kenya January 23, 2017. REUTERS/Thomas Mukoya 

Kenya Wildlife Services veterinarians monitor a tranquilised 5-year-old lioness named Nyala after setting up a radio collar on her neck to track her pride's movements at the Nairobi National Park near Nairobi, Kenya January 23, 2017. REUTERS/Thomas Mukoya 

Kenya Wildlife Services veterinarians monitor a tranquilised 5-year-old lioness named Nyala after setting up a radio collar on her neck to track her pride's movements at the Nairobi National Park near Nairobi, Kenya January 23, 2017. REUTERS/Thomas Mukoya 

Kenya Wildlife Services veterinarians monitor a tranquilised 5-year-old lioness named Nyala after setting up a radio collar on her neck to track her pride's movements at the Nairobi National Park near Nairobi, Kenya January 23, 2017. REUTERS/Thomas Mukoya 

A tranquilized leopard is carried out from a house in Kathmandu, Nepal June 1, 2016. REUTERS/Navesh Chitrakar TPX IMAGES OF THE DAY

A tranquilized leopard is carried out from a house in Kathmandu, Nepal June 1, 2016. REUTERS/Navesh Chitrakar

A tranquilized leopard lies near a toilet in a house in Kathmandu, Nepal June 1, 2016. REUTERS/Navesh Chitrakar

A Buddhist monk walks past a tiger before officials start moving them from Thailand's controversial Tiger Temple, a popular tourist destination which has come under fire in recent years over the welfare of its big cats in Kanchanaburi province, west of Bangkok, Thailand, May 30, 2016. REUTERS/Chaiwat Subprasom 

A sedated tiger is seen in a cage as officials start moving tigers from Thailand's controversial Tiger Temple, a popular tourist destination which has come under fire in recent years over the welfare of its big cats in Kanchanaburi province, west of Bangkok, Thailand, May 30, 2016. REUTERS/Chaiwat Subprasom 

A sedated tiger is stretchered as officials start moving tigers from Thailand's controversial Tiger Temple, a popular tourist destination which has come under fire in recent years over the welfare of its big cats in Kanchanaburi province, west of Bangkok, Thailand, May 30, 2016. REUTERS/Chaiwat Subprasom 

A sedated tiger is stretchered as officials start moving tigers from Thailand's controversial Tiger Temple, a popular tourist destination which has come under fire in recent years over the welfare of its big cats in Kanchanaburi province, west of Bangkok, Thailand, May 30, 2016. REUTERS/Chaiwat Subprasom 

A sedated tiger is stretchered as officials start moving tigers from Thailand's controversial Tiger Temple, a popular tourist destination which has come under fire in recent years over the welfare of its big cats in Kanchanaburi province, west of Bangkok, Thailand, May 30, 2016. REUTERS/Chaiwat Subprasom 

A sedated tiger is stretchered as officials start moving tigers from Thailand's controversial Tiger Temple, a popular tourist destination which has come under fire in recent years over the welfare of its big cats in Kanchanaburi province, west of Bangkok, Thailand, May 30, 2016. REUTERS/Chaiwat Subprasom 

A sedated tiger is stretchered as officials start moving tigers from Thailand's controversial Tiger Temple, a popular tourist destination which has come under fire in recent years over the welfare of its big cats in Kanchanaburi province, west of Bangkok, Thailand, May 30, 2016. REUTERS/Chaiwat Subprasom TPX IMAGES OF THE DAY

A sedated tiger is stretchered as officials start moving tigers from Thailand's controversial Tiger Temple, a popular tourist destination which has come under fire in recent years over the welfare of its big cats in Kanchanaburi province, west of Bangkok, Thailand, May 30, 2016. REUTERS/Chaiwat Subprasom 

A man directs a hippopotamus after it was shot with a tranquilizer dart at a flooded street in Tbilisi, Georgia, June 14, 2015. At least five people died and several are missing as a result of heavy rainfall and floods overnight in the Georgian capital Tbilisi, Georgian news agencies reported on Sunday. Animals from the city's zoo including tigers, lions, bears and wolves escaped from cages damaged by the rainfall. Some were captured or killed while the search for others goes on. REUTERS/Beso Gulashvili 

Staff members carry a tranquilised brown bear for its check-up by foreign veterinaries at the Four Paws Bear Sanctuary in Pristina, May 3, 2014. Six adult brown bears rescued from illegal private zoos all over Kosovo, and three recently found brown bear orphan cubs received thorough health check-ups and dental treatment. The four male adult bears Ero, Ari, Anik and Vini were castrated, so as not to be able to reproduce within captivity. Picture taken May 3, 2014. REUTERS/Hazir Reka (KOSOVO - Tags: ANIMALS SOCIETY) 

A Kenya Wildlife Service (KWS) veterinary staff prepares sleep sedatives to be used on selected elephants during a relocation exercise, aimed at relocating to a national park 10 elephants that were encroaching on community land, on the margins of the Ol Pejeta conservancy in central Kenya June 19, 2013. REUTERS/Siegfried Modola (KENYA - Tags: ANIMALS SOCIETY) 

Wildlife rescue workers scan a microchip which is planted in a tranquilised lion on the outskirts of Bangkok June 19, 2013. Thai police they confiscated more than a thousand wildlife animals on June 10, 2013 and will investigate to verify their origin. Almost 1,000 sugar gliders, 14 white lions, 12 peacocks, 17 marmosets and many other wild animals were found in cages in the suburbs of Bangkok REUTERS/Chaiwat Subprasom (THAILAND - Tags: SOCIETY ANIMALS CRIME LAW) 

An activist from Austrian NGO "Four Paws" tranquilises bears that are are seen in a cage at a private zoo located next to a restaurant in the Kosovo town of Prizren, about 90 km (56 miles) southwest of the capital Pristina, May 22, 2013. Kosovo has launched a campaign, helped by "Four Paws", to seize wild bears held in restaurants and private zoos, responding to concerns over their dwindling numbers in the Balkan country's mountainous border areas. Picture taken May 22, 2013. REUTERS/Hazir Reka (KOSOVO - Tags: ANIMALS ENVIRONMENT SOCIETY) 

Rangers hold a rhino during a media demonstration at the Rhino and Lion Nature Reserve in the Cradle of Humankind, outside Johannesburg February 9, 2012. A group of animal conservationists in South Africa accidentally killed a rhinoceros they were attempting to make safe from poachers in a botched public relations event. Spencer the rhino went into convulsions and died after he was shot with a tranquiliser dart in front of a crush of TV cameras and photographers who had been invited to document an operation to insert a poison capsule into his horn. Picture taken February 9, 2012. REUTERS/Siphiwe Sibeko (SOUTH AFRICA - Tags: ANIMALS) 

Rangers push a rhino during a media demonstration at the Rhino and Lion Nature Reserve in the Cradle of Humankind, outside Johannesburg February 9, 2012. A group of animal conservationists in South Africa accidentally killed a rhinoceros they were attempting to make safe from poachers in a botched public relations event. Spencer the rhino went into convulsions and died after he was shot with a tranquiliser dart in front of a crush of TV cameras and photographers who had been invited to document an operation to insert a poison capsule into his horn. Picture taken February 9, 2012. REUTERS/Siphiwe Sibeko (SOUTH AFRICA - Tags: ANIMALS) 

Rangers hold a rhino during a media demonstration at the Rhino and Lion Nature Reserve in the Cradle of Humankind, outside Johannesburg February 9, 2012. A group of animal conservationists in South Africa accidentally killed a rhinoceros they were attempting to make safe from poachers in a botched public relations event. Spencer the rhino went into convulsions and died after he was shot with a tranquiliser dart in front of a crush of TV cameras and photographers who had been invited to document an operation to insert a poison capsule into his horn. Picture taken February 9, 2012. REUTERS/Siphiwe Sibeko (SOUTH AFRICA - Tags: ANIMALS) 

A Conservationist carries a darted fallow deer for relocation from Robben Island, off Cape Town, April 24, 2010. About 75 of the non-indigenous deer are being relocated to the Lions Rock sanctuary by the Four Paws (Vier-Pfoten) conservation group. In recent years rabbits, cats and deer have been culled to lessen the negative environmental effects to the island, a World Heritage site where former President Nelson Mandela spent much of his 27 year incarceration. REUTERS/Mike Hutchings (SOUTH AFRICA - Tags: SOCIETY ENVIRONMENT ANIMALS) 

Darted fallow deer await relocation from Robben Island, off Cape Town, April 24, 2010. About 75 of the non-indigenous deer are being relocated to the Lions Rock sanctuary by the Four Paws (Vier-Pfoten) conservation group. In recent years rabbits, cats and deer have been culled to lessen the negative environmental effects to the island, a World Heritage site where former President Nelson Mandela spent much of his 27 year incarceration. REUTERS/Mike Hutchings (SOUTH AFRICA - Tags: SOCIETY ENVIRONMENT ANIMALS) 

Zoo officials carry a tranquilized tiger inside the Assam State Zoological cum Botanical Garden in Guwahati January 30, 2010. Two adult tigers on Saturday escaped from an enclosure at the Assam Zoo triggering panic among nearly 10,000 visitors, zoo officials said. Both the tigers were later tranquilized and taken to their cages, the officials added. REUTERS/Utpal Baruah (INDIA - Tags: ANIMALS SOCIETY) 

One of the two adult tigers, with a tranquilizer dart on its body, walks inside the Assam State Zoological cum Botanical Garden in Guwahati January 30, 2010. Two adult tigers on Saturday escaped from an enclosure at the Assam Zoo triggering panic among nearly 10,000 visitors, zoo officials said. Both the tigers were later tranquilized and taken to their cages, the officials added. REUTERS/Utpal Baruah (INDIA - Tags: ANIMALS IMAGES OF THE DAY) 

Members of Forestry Institute rush around a brown bear after it was shot with a tranquilizer dart in the outskirts of Sinaia, 140 km north of Bucharest, June 15, 2009. Local authorities and members of the Forestry Institute started an operation to capture and relocate about 25 bears after many started to roam in the town in search for food. With half of Europe's brown bears - roughly 6,000 - living in the Carpathians mountains environmentalists and authorities are struggling to keep the wild animals and residents in mountain towns safe from each other. REUTERS/Radu Sigheti (ROMANIA ENVIRONMENT ANIMALS SOCIETY) 

George Sirbu from the Forestry Institute carries a brown bear cub to a cage after it was shot with a tranquiliser dart in the outskirts of Sinaia, 140 km north of Bucharest, June 15, 2009. Local authorities and members of the Forestry Institute started an operation to capture and relocate about 25 bears after many started to roam in the town in search for food. With half of Europe's brown bears - roughly 6,000 - living in the Carpathians mountains environmentalists and authorities are struggling to keep the wild animals and residents in mountain towns safe from each other. REUTERS/Radu Sigheti (ROMANIA ENVIRONMENT ANIMALS) 

A brown bear is measured after being shot with a tranquiliser on the outskirts of Sinaia, 140 km (87 miles) north of Bucharest, June 15, 2009. Local authorities and members of the Forestry Institute started an operation to capture and relocate about 25 bears after many started to roam the town in search for food. With half of Europe's brown bears - roughly 6,000 - living in the Carpathians mountains, environmentalists and authorities are struggling to keep the wild animals and residents in mountain towns safe from each other. REUTERS/Radu Sigheti (ROMANIA ANIMALS SOCIETY IMAGES OF THE DAY) 

A kangaroo that escaped from the culling pen after it had been shot with a tranquilising dart is put into a bag by workers on a military base in Canberra May 19, 2008. Australia's military began culling hundreds of kangaroos at a defence base on Friday, enraging animal rights activists who vowed to stop the killings. REUTERS/Stefan Postles (AUSTRALIA) 

Some of the kangaroos that are to be culled are seen on the Department of Defence property in Belconnen, Canberra May 17, 2008. Authorities said kangaroos threatened other local species through overgrazing. The Australian government had withdrawn support for a plan to relocate the kangaroos because it would cost millions of dollars and was not considered an effective use of taxpayers' money, the department said. The kangaroos will be tranquilised with a dart gun then injected with the deadly chemical Lethabarb. REUTERS/Stefan Postles (AUSTRALIA) 

The kangaroo killing pen cloaked by hessian, with freezers at the ready, is seen on the Department of Defence property in Belconnen, Canberra May 17, 2008. Authorities said kangaroos threatened other local species through overgrazing. The Australian government had withdrawn support for a plan to relocate the animals because it would cost millions of dollars and was not considered an effective use of taxpayers' money, the department said. The kangaroos will be tranquilised with a dart gun then injected with the deadly chemical Lethabarb. REUTERS/Stefan Postles (AUSTRALIA) 

Kenya Wildlife Service veterinary officials prepare tranquiliser darts for elephants at the Maasai Mara National Reserve in Kenya's Rift Valley region, 200 km (124 miles) from Nairobi, March 18, 2008. Elephants had been fitted with the collars in August 2006 to monitor their ranging and movement patterns and establish whether the population remained in the Mara region. The exercise on Tuesday was to de-collar the elephants and study their movements based on information gathered from the the collar. REUTERS/Antony Njuguna (KENYA) 

An elephant rests after being shot with a tranquiliser dart by the Kenya Wildlife Service veterinary officials at the Maasai Mara National Reserve March 18, 2008. Elephants had been fitted with GPS collars in August 2006 to monitor their ranging and movement patterns and establish whether the population remained in the Mara region. The exercise on Tuesday was to de-collar the elephants and study their movements based on information gathered from the the collar. REUTERS/Antony Njuguna (KENYA) 

Kenya Wildlife Service veterinary officials prepare for take off on a mission to tranquilise elephants at the Maasai Mara National Reserve March 18, 2008. The elephants were fitted with GPS collars in August 2006 to monitor their ranging and movement patterns and establish whether the population remained in the Mara region. The exercise on Tuesday was to de-collar the elephants and study their movements based on information gathered from the the collar. REUTERS/Antony Njuguna (KENYA) 

An elephant rests after being shot with a tranquiliser dart by the Kenya Wildlife Service veterinary officials at the Maasai Mara National Reserve March 18, 2008. Elephants had been fitted with GPS collars in August 2006 to monitor their ranging and movement patterns and establish whether the population remained in the Mara region. The exercise on Tuesday was to de-collar the elephants and study their movements based on information gathered from the the collar. REUTERS/Antony Njuguna (KENYA) 

A zoo worker pretends to shoot a tranquiliser dart at another worker dressed as an orang-utan as part of an animal escape drill at a zoo in western Tokyo February 27, 2007. Zoo workers practiced surrounding the escapee with nets before pretending to shoot it with a tranquilising dart and returning it to its enclosure. REUTERS/Michael Caronna (JAPAN) 

A zoo worker dressed as an orang-utan pretends to escape from an enclosure as part of an animal escape drill at a zoo in western Tokyo February 27, 2007. Zoo workers practised surrounding the escapee with nets before pretending to shoot it with a tranquilising dart and returning it to its enclosure. REUTERS/Michael Caronna (JAPAN) 

Children are frightened by a zoo worker dressed as an orang-utan pretending to escape from an enclosure as part of an animal escape drill at a zoo in western Tokyo February 27, 2007. Zoo workers practiced surrounding the escapee with nets before pretending to shoot it with a tranquilising dart and returning it to its enclosure. REUTERS/Michael Caronna (JAPAN) 

A zoo worker dressed as an orang-utan is interviewed by reporters following an animal escape drill at a zoo in western Tokyo February 27, 2007. Zoo workers practised surrounding the escapee with nets before pretending to shoot it with a tranquilising dart and returning it to its enclosure. REUTERS/Michael Caronna (JAPAN) 

A zoo worker dressed as an orang-utan falls after being "shot" by another zoo worker with a simulated tranquiliser dart as part of an animal escape drill at a zoo in western Tokyo February 27, 2007. Zoo workers practiced surrounding the escapee with nets before pretending to shoot it with a tranquilising dart and returning it to its enclosure. REUTERS/Michael Caronna (JAPAN) 

A zoo worker dressed as an orang-utan pretends to attack a zoo worker as part of an animal escape drill at a zoo in western Tokyo February 27, 2007. Zoo workers practised surrounding the escapee with nets before pretending to shoot it with a tranquilising dart and returning it to its enclosure. REUTERS/Michael Caronna (JAPAN) 

Zoo workers carry an anaesthetized African lion named "Prince" at the Ramat Gan Safari near the central Israeli city of Tel Aviv December 10, 2006. The lion was transported to a zoo in Zarka, Jordan, as a donation. REUTERS/Gil Cohen Magen (ISRAEL) 

Hunter Anton Marincin and veterinarian Tamara Cehovin (R) examine a tranquilised female bear in Masun, southern Slovenia on April 24, 2006. [The three and a half year-old bear called Paloma will be released in Pirinea (south-east France). Four female bears and one male will be relocated, after an agreement between France and Slovenia.] 

Hunter Anton Marincin and veterinarian Tamara Cehovin (R) examine a tranquilised female bear in Masun, southern Slovenia on April 24, 2006. The three and a half year-old bear called Paloma will be released in Pirinea (south-east France). Four female bears and one male will be relocated, after an agreement between France and Slovenia. Picture taken April 24, 2006. REUTERS/Srdjan Zivulovic 

A zoo worker checks whether the mock gorilla is conscious after pretending to have shot it with a tranquiliser gun during a drill in Tokyo February 21, 2006 to prepare the Ueno zoo to deal with a situation in which a ferocious animal escapes from its enclosure. About 150 people including zoo employees, fire department and police officials took part in the annual drill. REUTERS/Yuriko Nakao 

A zoo worker checks whether the mock gorilla is conscious after pretending to have shot it with a tranquiliser gun during a drill in Tokyo February 21, 2006 to prepare the Ueno zoo to deal with a situation in which a ferocious animal escapes from its enclosure. About 150 people including zoo employees, fire department and police officials took part in the annual drill. REUTERS/Yuriko Nakao 

Locals and Kenyan Wildlife Service wardens help move a tranquilised elephant escaped from the Amboseli National Park, Kenya. Locals help Kenyan Wildlife Service wardens to move a tranquilised elephant into a vehicle in Kitengela in southeast Nairobi May 19, 2005. Two male African elephants escaped from the Amboseli National Park and were traced down in Kitengela, some 200 km (124 miles) from the park, before bring tranquilised and sent back in trucks. REUTERS/Stringer 

Conservationists examine a tiger after it was tranquilised in a South African game reserve in the country's Free State province. Conservationists examine a tiger after it was tranquilised in a South African game reserve, in the country's Free State province, March 12, 2005. The animal is one of four rare Asian tigers, all brought up in captivity, that have been brought to Africa to learn how to hunt as part of a rewilding programe. The ultimate goal is for them to breed and impart their hunting skills to their offspring - who will be then be sent to a reserve in China.-Picture taken March 12, 2005-REUTERS/Ed Stoddard FOR RELEASE WITH STORY BC-ENVIRONMENT-TIGERS- 

Indian forest officials carry a tranquilised female leopard after it was caught in a residential area in Bombay June 28, 2004. The leopard which had strayed into a densely populated residential area was caught after several hours of chasing. A series of leopard attacks this year has struck terror in India's financial hub of nearly 13 million, killing ten people in June alone and fourteen this year. REUTERS/Punit Paranjpe AD/WS 

An Indian veterinary doctor injects additional tranquiliser in a female leopard after it was caught from a residential area in Bombay June 28, 2004. The leopard which had strayed into a thickly populated residential area was caught after several hours of chasing. A series of leopard attacks this year has struck terror in India's financial hub of nearly 13 million, killing ten people in June alone and fourteen this year. REUTERS/Punit Paranjpe AD/ACM 

Indian forest officials carry tranquilised female leopard after it was caught from a residential area in Bombay June 28, 2004. The leopard which had strayed into a thickly populated residential area was caught after several hours of chasing. A series of leopard attacks this year has struck terror in India's financial hub of nearly 13 million, killing ten people in June alone and fourteen this year. REUTERS/Punit Paranjpe AD/CRB 

Indian forest officials carry tranquilised female leopard after it was caught from a residential area in Bombay June 28, 2004. The leopard which had strayed into a thickly populated residential area was caught after several hours of chasing. A series of leopard attacks this year has struck terror in India's financial hub of nearly 13 million, killing ten people in June alone and fourteen this year. REUTERS/Punit Paranjpe AD/CRB 

Indian forest officials carry a tranquilised female leopard after it was caught in a residential area in Bombay June 28, 2004. The leopard, which had strayed into a thickly populated residential area, was caught after several hours of chasing. A series of leopard attacks this year has struck terror in India's financial hub of nearly 13 million, killing ten people in June alone and fourteen this year. REUTERS/Punit Paranjpe AD/TW