But after appearing on websites, newspapers, magazines and television shows around the world, Mr Slater is now facing a legal battle with Wikimedia after the organisation added the image to its collection of royalty-free images online. The Wikimedia Commons is a collection of 22,302,592 images and videos that are free to use by anyone online, and editors have included Mr Slater's image among its database.
The Gloucestershire-based photographer now claims that the decision is jeopardising his income as anyone can take the image and publish it for free, without having to pay him a royalty. He complained To Wikimedia that he owned the copyright of the image, but a recent transparency report from the group, which details all the removal requests it has received, reveals that editors decided that the monkey itself actually owned the copyright because it was the one that pressed the shutter button.
Mr Slater now faces an estimated £10,000 legal bill to take the matter to court.
"If the monkey took it, it owns copyright, not me, that's their basic argument. What they don't realise is that it needs a court to decide that," he said.
The image has been removed in the past when he complained, but different editors regularly upload it once again.
"Some of their editors think it should be put back up. I've told them it's not public domain, they've got no right to say that its public domain. A monkey pressed the button, but I did all the setting up."
Mr Slater said that the photography trip was extremely expensive and that he has not made much money from the image despite its enormous popularity.
"That trip cost me about £2,000 for that monkey shot. Not to mention the £5,000 of equipment I carried, the insurance, the computer stuff I used to process the images. Photography is an expensive profession that's being encroached upon. They're taking our livelihoods away," he said.
"For every 100000 images I take, one makes money that keeps me going. And that was one of those images. It was like a year of work, really."