Cecil the lion death: US opens investigation into killing as hunter Walter Palmer faces calls to return to Africa and 'face justice'

US authorities have opened an investigation into the death of Cecil the lion in Zimbabwe, as the Minnesota dentist accused of illegally hunting and killing it faced calls to return to Africa and “face justice”.

The head of the US Fish and Wildlife Service, Dan Ashe, promised his agency would “go where the facts lead us” in trying to get to the bottom of the killing of the big cat who, with his jet black main, had become a fixture of the Hwange National Park in the west of Zimbabwe. Known affectionately as Cecil, the lion had also been fitted with a tracking collar by researchers at Oxford University.

Walter Palmer, who paid $50,000 (£32,000) to hunt and kill the lion remained in hiding and the agency said it had been unable to contact him. His dental office in Bloomington, a suburb of Minneapolis, was closed and in a message he warned his patients that it would remain so for the foreseeable future.

The Fish and Wildlife Service is expected to investigate whether the dentist may have been part of a conspiracy to violate the 1900 Lacey Act, which bars the trading of wildlife that has been illegally killed. “We are gathering facts about the issue and will assist Zimbabwe officials in whatever manner requested,” said Laury Marshall Parramore, an agency spokeswoman.

Betty McCollum, a Democrat Congresswoman from Minneapolis, said officials should investigate “whether US laws were violated related to conspiracy, bribery of foreign officials, and the illegal hunting of a protected species or animal”. She added: “To bait and kill a threatened animal, like this African lion, for sport cannot be called hunting, but rather a disgraceful display of callous cruelty.”

Former Speaker of the House Newt Gingrich said “the entire team that killed the lion Cecil should go to jail, including the Minneapolis dentist”.

The Oxford-based Wildlife Conservation Research Unit, whose staff have worked closely with lions in Hwange and had fitted Cecil’s tracking collar, warned that when one male lion dies, others in the pride may turn on animals associated with it, including its cubs. The researchers said: “Despite our sadness, as scientists, we seek to learn from this event, and to find some benefit from it. We are working hard to study the consequences of Cecil’s death on his pride and their neighbours, so that we learn as much as possible.”

In Zimbabwe, Mr Palmer’s hunt guide has been charged with illegally luring the lion out of its sanctuary inside the national park. The US embassy in Harare said it had no information about any extradition request for Dr Palmer, but the head of the Zimbabwe Conservation Task Force, Johnny Rodriguez, said that should be the next step. “People should be accountable for whatever crimes, whatever the case is,” he told the Minneapolis Star Tribune, adding it was “imperative that Palmer face justice.”

Dr Palmer has said that while he regretted the death of Cecil, he had relied on his guides to make sure his quarry had been legal.

Separately, in a long-scheduled vote, the UN General Assembly last night adopted a resolution to stop illegal wildlife trafficking.