I think Basenji's just are very alert dogs, and at night there is a lot of "activity" outside we may not see, but they do!
I think that's a big part of it. As they say, "ignorance is bliss". Basenjis are certainly not ignorant when it comes to their surroundings. I noticed Kananga always has his ears back when we're outside at night, or certain times during the day. He can sense something and it makes me nervous at times. :o
But this is what makes them great hunters and generally great at surviving out in the open. They are smart, and with that comes anxiety since they are aware.