User blog comment:Lord Loss/Monster Hunter Theory... Blog/@comment-4212769-20120919100246/@comment-4212769-20121002193406

I recently watched this video:

http://www.youtube.com/watch?v=DVE9DTzv3Bw&feature=relmfu

After the White Lagiacrus died, the fight against Azure Rathalos and Brachydios begins. It seems that the slime on its arms gets black/dark and it has to lick them to make them normal again. In this black/dark status it cannot reveal explosive slime to the ground or hunter but after it licks them it works again.

So my guess is that it (besides the cleaning) needs to lick them to keep them moist. Without that moisture the slime loses its explosive characteristics.