Kill 5 Zone dogs, you will encounter these on your first mission after reaching the ark, The first chance to meet them is off the track in the Hammond's cabin zone, so you might walk past these if your not exploring of the track. There is another two in the next zone if you take the right optional "secret" path into the woods instead of climbing the ladders to the left. This will lead you to another zone which has two more guarding the camp. Which will be enough to grant you this one. I pretty sure there will be more and all the ones mentioned has been optional kills and is not strictly required but you most likely want to kill these so you don't become under leveled.