From Creatures Wikia
Yautja Norns have a CFE based genome and are very aggressive. They share some similarities with Sabertooth Norns in that they have a strong immune system and are picky eaters and avid hunters to a degree similar to Beowulf Norns and Hardman Norns. They will hunt down and kill any Grendel they see, so it is best to keep any non-aggressive grendels away from them. They have peculiar mating behaviours, where female Yautjas will frequently Hit their mate.
The Yautja Norns are bundled with several agents: the Jungle Grass; which installs tall grass in either the Norn Terrarium or Grendel Jungle, Crunchy Beetles; an edible Critter, and the Death Update, which leaves a skull behind whenever a Grendel dies.
The Yautja story can be read here.
|Spoiler warning: Plot or ending details follow.|
The Lone Shee discovered the Yautja Norns after an alien ship crashed into the Capillata. The alien abruptly left in their own ship, leaving behind several tools and a puddle of goop. After scanning, the yellow-green goop seems to be blood. The Lone Shee spliced the DNA from the spilt blood into a Norn egg, and the Yautja Norn breed was created.