Behind-the-scenes photo from a producer's blog: https://josephmallozzi.com/2010/07/20/july-20-2010-charting-jellys-progress-the-masked-soundtrack-last-days-of-atlantis-ii/
Direct link to a full quality version of the image: https://i0.wp.com/josephmallozzi.com/wp-content/uploads/2010/07/bob-and-jason-3.jpg
It originally wasn't a wig in his first several episodes. But when Momoa wanted to cut his hair for personal reasons, the producers did not want him to because the hair was such a staple part of the character. So they had his hair cut and professionally made into a wig so he could keep having that same hairstyle.
