That was really unfair. But I think I got it - I had to use my patented piece of software unsuprisingly called MonkeyCounter™. It turns out there are 39±2 monkeys in the image.

The ambiguity arose from the fact that it may have counted a rock as a monkey; it really needs a higher resolution image to be more acurate.

Well, if I made it easy, where would be the fun? (oh, and I had a higher resolution version of that image, but there's a limit on uploads, and it had to be resized...)

Good effort though.