Two French tourists have spent a night in jail after failing to raise the $4000 each they were fined after pleading guilty to setting a quokka on fire.

Thibaud Valette, 24, and Jean Batrikian, 18, were charged with animal cruelty for the offence committed on Rottnest Island, off the coast of Perth, on April 3, the ABC reports .

One of the men ignited an aerosol spray with a lighter and singed the quokka while the other recorded it on his mobile phone.

The pair's lawyer told Fremantle Magistrates Court yesterday they now feared for their safety after being abused online.

In handing down the $4000 fine, Magistrate Elizabeth Langdon dismissed the pair's claim that they did not intend to harm the animal.

She said the $4000 fine was necessary to act as a deterrent.

The pair spent last night in custody after failing to raise enough money to pay the fine.

The maximum penalty for animal cruelty is a $50,000 fine and five years in jail.

Quokkas are small, endangered marsupials and are protected under state and federal legislation.

They are almost exclusively found on Rottnest Island after their numbers on the mainland plummeted following European settlement.

There are still some small populations on the mainland.