I was somewhat amazed by those stats: I thought Americans would have contributed the most. Is there something I should know about Germans and Giraffes that I do not know?
It looks like this started in Europe. A mainstream American website usually sees a 1:2 domestic to international ratio while a niche/startup website usually starts out with the opposite (actually more like 10:1 I would guess.) This follows that pattern except the U.S. is part of the international piece of the pie.
There is this one submitter of Giraffes[1], responsible for two percent of all German giraffes, or this one[2], responsible for nearly five percent. I didn’t even have to look all that hard to find them.
[1] "I found 4 085 giraffes created by people named Sanne!"
[2] "I found 9 988 giraffes created by people named Ediktonia!"
The actual statistic is that 2% of all Germans who submitted giraffes were named Sanne and 5% were named Ediktonia. It doesn't say they were all the same person.
Sanne has actually only submitted 15 pictures. This is one of them, http://www.onemilliongiraffes.com/?id=54374 There are ~2000 giraffes on one page. Ediktonia has similar images.
Personally, I think these works are kind of taking the piss.