The pictures by Terje Helleso came into question when Gunnar Gloerson, a conservationist for the Swedish Association for Hunting and Wildlife Management, examined a suspicious-looking photo of a lynx, The Local reported Monday.
"Doesn't this lynx in the July greenery have a winter fur? How about the lynx that's reflected in the pool, is it walking in the air or on land, and can you really see the paws in that angle?" Gloerson wrote in a blog Aug. 26.
Gloerson questioned claims by Helleso that the photographer has seen 150 lynx in nine months, when Gloersen had only seen 15 in 52 years of wildlife study.
On Saturday, Helleso admitted to the photo manipulations.
The Swedish Environmental Protection Agency, which named Helleso its nature photographer of the year in 2010, said it would review whether Helleso would be allowed to retain his title.