Animal rights group Peta is offering £10,000 ($17,000) to anyone who helps police track down two men who were filmed kicking a squirrel into the Grand Canyon.
The men, who are believed to be French, sparked global outrage on social media sites last week after a video showed them luring the animal to the edge of the canyon using breadcrumbs before one of them kicked it off.
They are now wanted by the US authorities though officials who run the Nevada national park say their chances of tracking down the pair are remote.
Launching an appeal to track down the "heartless thug" who kicked the defenceless animal to its death, the US, UK and French branches of activist and campaign group Peta have come together to put forward a reward of £10,000 to anyone with information that leads to an arrest.
Ben Williamson, a spokesperson for Peta UK said that people who abuse animals are a "danger to everyone" and must be stopped "before they act again".
"It is imperative that any community faced with a sadistic and violent act such as this take measures to find the culprit or culprits and bring them to justice," he said.
Grand Canyon Chief Ranger Bill Wright said that if the men are found they could face a charged of disturbing or harassing wildlife — a federal petty offence that carries a maximum six months in jail and or a $5,000 fine.
He said he felt it was unlikely the men could be prosecuted for animal cruelty as that would require the authorities to find the squirrel and prove it had been killed or injured – which would mean climbing down into the canyon. which has an average depth of 1 mile (1.6km).
The clip was uploaded to YouTube by tourist Jonathan Hildebrand, who said that he filmed the act but was unaware what the man planned to do. He said he "did not realise what was happening until it was too late."
The video has since been removed from YouTube for violating its terms of service.