Nothing mysterious at all, of course. Look closely at the dark outline.
How do you see a dark-coloured dog in the fields and forest around the house, when it's pitch black outside?
Answer - you tie bicycle lamps to his collar.
They're the very small LED ones (they flash as well!) so they're small enough to keep them attached all the time,
just pressing the button to turn them on when he goes out.
With this system it's much easier to see where he is at night than in the day.