Ok, well go ahead and feel free to catalog every single "furry" artwork ever created on the internet and sort them as "research" and "not research".
If you were to go on a furry-specific art site such as FA, count how many images were uploaded under the "General Furry Art (Tame)" category within 24 hours, and compare it to the number of images were uploaded under "General Furry Art (Mature)" within the same time period, you would find a lot more under tame.
By the way, google images doesn't sort by "popularity". It sorts by relevance.
But I believe popularity is one of the factors that google considers in determining relevance?