good photo, just a couple suggestions: crop the top 1/5 of the image, and a little off the bottom, then adjust the levels, if you have photoshop, to add a little contrast, make the shadows a little darker.
Well, a great subject (tortoise by the way!) and it is framed. Light looks a little weak and flat so shooting earlier or later in the day would help make definition more interesting.
The colors look washed and the "green on green" look of this photo is a little to much. I also find the contrast to be a little to much as it could be the cause of the washiness. It also appears to be a little OoF but against could be due to the contrast or white balance. Good luck in this challenge. <5>