Killing of Cecil the lion triggers probe by US agency

Palmer, whose practice is in suburban Minneapolis, has admitted to killing the 13-year-old lion and tourist attraction, in July. Questions have been raised by the Zimbabwean government and animal conservationists about Cecil's death outside the Hwange National Park, where he was the head of two lion prides.

The best known lion in Zimbabwe, Cecil is said to have been lured from the park with bait, shot with an arrow, tracked for 40 hours, shot dead with a rifle and then beheaded and skinned.

Cecil was wearing a GPS collar as part of a research project run by Oxford University.

The administration of President Barack Obama has made a major push to combat wildlife trafficking, issuing a national plan earlier this year to address it and cracking down on domestic trade in African elephant ivory.

With some of the strongest laws in the world to protect endangered species, the U.S. government has attempted to prevent the slaughter of such animals internationally by targeting the multibillion-dollar market for illegal wildlife items.

In 2014, the service proposed listing the African lion as threatened under the U.S. Endangered Species Act. The proposal, which is being finalized, would create a permit process for importing lion trophies from countries that properly manage the species.

Estimates vary on how many lions are left in Africa, with a low end of fewer than 20,000. There has been a significant decline in the African lion population over the past 20 years.

The Lacey Act can be used to prosecute anyone who violates wildlife protections under the Convention on International Trade in Endangered Species (CITES).

The African lion is protected under CITES, which requires exporters of the animal to get a permit from its home country. The lion or its parts cannot be imported into the United States unless it meets CITES requirements.