Demonstrators in 70 cities around the world are preparing to take part in a mass protest against the organised hunting of endangered wildlife and importation of animal body parts.
The coordinated action on Saturday will call on world leaders to close loopholes that leave species including lions, giraffes, elephants and rhinos at risk of being driven to extinction.
In London, hundreds of demonstrators are set to march on Downing Street to deliver a letter to Theresa May signed by celebrities including Star Trek actor William Shatner.
Britain is among the nations most responsible for allowing wildlife annihilation to continue, according to the Campaign to Ban Trophy Hunting (CBTH). The UK is one of 12 countries whose hunters have taken at least 1,000 trophies and brought home more than a ton of ivory.
Hunters globally have taken home 100,000 African elephant trophies since the 1980s, campaigners said.
Elephant populations plummeted from 1.3 million to just over 400,000 over the same period, according to CBTH investigators.
Britain’s laws on trophy hunting are even more lenient than those in the US, say protest organisers from Action for Elephants UK. The regulations have allowed 2,500 animal parts to be imported over the past decade – many from cheetahs, lions, leopards, hippos, bears and zebras.
Marches calling for importation of wildlife trophies to be outlawed will also be held in Birmingham and Bristol.
About two tons of ivory have also been brought home by British hunters, as well as elephant ears, trunks, feet, tails and skins.
Legal trophy hunting is driving species already hit hard by poaching, habitat loss and human-wildlife conflict further towards extinction.
From 1985 to 2015 the amount of ivory poached rose 12-fold, the CBTH found.
The protests are aimed at leaders of countries signed up to the Convention on International Trade in Endangered Species of Wild Fauna and Flora (Cites), a treaty regulating wildlife trade. Cites is meeting next month in Sri Lanka, where African nations are expected to push for lower protections for elephants and reopen the ivory trade.
Cites allows hunters to have permits to kill even protected animals facing extinction but activists are calling for an end to such practices. Demonstrators also want a ban on captive breeding of protected animals for their parts, which they say fuels the illegal trade.
MPs from all parties have signed a parliamentary motion calling for a UK ban on trophy imports.
The letter, signed by more than 70 wildlife groups, MPs and lords, tells the prime minister: “The government can expect full and enthusiastic support from the British public for this move.”
Shatner added: “How does the insanity of killing these magnificent animals, of which there is only a handful left, conserve them? A trophy animal is the best of the brightest of the breed.”
Biologist Ian Redmond said trophy hunting killed the animals with the strongest genes most sought-after by tourists and filmmakers. He added that in elephant populations, knowledge of surviving extreme weather is held by elders, so killing them reduces a group’s survival chances.
The Department for Environment, Food and Rural Affairs said that under Cites rules trophies can be imported only under strict regulations.