His PH is any manatee or walrus from what I can tell. I killed him probably 6-8 times so far and every time he had the tiny pearl seal. I usually saw him at the first walrus spawn on the ledge as you zone right in from cscar past the first Ulthork spawn, or up ahead on the left or right shore as you face the waterfall. There are 4 spawns there. I havent camped much on the upper area but I saw him up there vicinity of the well twice so far.
He hits the same as the other massive manatee, summons, doesnt run, kos, larger aggro range, social-brings adds (walrus/ulthork/seahorse/whatever), fast swimmer, will warp to you if caught on something, and is slowable.