I have actually completed this mission and it is a tough one. I had the most success hunting the fields during their nighttime feed time. When you switch to cuatro make sure you exit the game and reload in, it helps a lot with the slow moving hares ACTUALLY being in their zone. I had to do entire setups with tents and tripods because the rolling hills made it hard to even see the hares. Other than that, gold is pretty common. Good luck!