We live in a flat that's been built into the roof space of an oldish house, so above our ceilings there is space, closed space, sometimes only 10 cm sometimes up to 1,5 m. A marten moved in, it sounds as if some serious building work is being done and she comes home drunk every morning for some dancing practice. We (management, caretaker, me, chimney sweep, random roofers) have not been able to find her entrance point. And then there is Sev. He is following from below, trying to get as close to the marten as he can possibly get. He sits on wardrobes staring at the ceiling. Just now he stood on his hind legs on my Kallax, reaching up as far as he could, then bent to the left and fell down on my back.
Martens live up to 10 years. Seigh.