The image, by Canadian photographer Thomas Vijayan, is called The World is Going Upside Down. It beat 8,000 entries from around the globe to win the top prize of £1,500.
“Thomas’s image is really unique, and immediately stood out to the judging panel,” said Will Nicholls, founder of Nature TTL.
“The unique perspective and composition means you are immediately trying to figure out what exactly you are looking at.”
Mr Vijayan took the photo in Borneo, where he selected a tree that was in the water so he could get a good reflection of the sky and create the upside-down effect.
“This image means a lot to me because presently the orangutan population is reducing at an alarming rate,” he said.
“Trees over 1,000 years old – which are a major asset to our planet – are being cut down for palm oil plantation.
“As humans we have a lot of alternative choices to replace the oil, but the orangutans don’t have any options other than losing their home.”
Vijayan’s photo also won first place in the Animal Behaviour category.
Here are winning images from other categories, with descriptions by the photographers.