I assumed this was a buff that occurred in the months I didn't play ZK. Makes them 10x more deadly, and they seem to be somewhat of a deciding factor in almost every big sea game now. It's much harder to chase them down with a pack of snakes or hunters as they can take down at least 1 or 2 units while running.
There was a game where Wolas and I both had 7 or 8 serpents in dueling packs... great fun.