The outcry over the killing of Cecil came as the UN General Assembly last week adopted the first-ever resolution which is aimed at combating illicit trafficking in wildlife.

The resolution urges all nations to take decisive steps to “prevent, combat and eradicate” the illegal trade in wildlife, in terms of both supply and demand. It is not legally binding, but reflects growing concern over an escalation in poaching and trafficking, particularly in elephant and rhinoceros horns.

Last week it also emerged one of only five remaining critically endangered northern white rhinoceros had died at a Czech zoo. The animal has been hunted to the brink of extinction for its highly prized horn. Only one male northern white rhino is left - who may be too old to breed – and has been placed under 24-armed guard in Kenya. His horn has been cut off to deter poachers.

An analysis by WWF and the Zoological Society of London last year found the number of wild animals on earth has halved in the past 40 years, with much of the decline being caused by human action - such as hunting and destruction of their habitats.

The study found that among the species most affected included the hoolock gibbon of Bangladesh, the African lion in Ghana’s Mole national park, short-beaked common dolphins in the Ionian Sea in Greece and forest elephants in central Africa.

In the UK, populations of farmland birds such as the grey partridge were found to have declined by 50% since 1970.

It is illegal to import animals listed as threatened or endangered into the US as sport hunting trophies. Last October the US Fish and Wildlife Service considered listing the African lion under the act, but it has not been added yet and it is therefore legal to import lion trophies into the US. It is believed Cecil’s head - which was severed by the hunters - has been confiscated by wildlife officials in Zimbabwe. The US Fish and Wildlife Service has said it is investigating the killing of Cecil and whether any US laws were broken.

America lawmakers have also announced they are looking at introducing legislation to curb trophy hunting in the wake of Cecil’s death. New Jersey senator Bob Menendez said he will introduce an act which will extend import and export protections for endangered species.

Meanwhile US dentist Walter Palmer, who has been keeping a low profile since it emerged he was the hunter who killed Cecil, yesterday received public support from musician Ted Nugent, an outspoken advocate for hunting.

In an interview with the Rita Cosby Show on WABC radio in New York, Nugent, 66, railed against people who were upset about the killing, saying the outrage was because the lion was given a name, Cecil.

He said getting upset about Cecil but not other lions was "disingenuous and tragically dishonest".