It's one of the activities provided at AKL. It's usually long enough after sunset so that it's dark--you can check the activities board in the main lobby, or you may be able to call the front desk and ask what time it is.
They usually meet out behind the pool on the edge of the savannah there--if you walk out to the pool area and along the left side of the pool, back behind there along the fence there will be a CM with a couple of pairs of night vision goggles you can use to look at the animals. (They usually put some food out to bring them over to that area.)