That is one looong tunnel, but it offers up an interesting perspective of the apes as they cross over the heads of their human relatives. Is that hay hanging out of the tunnel?
Yes, that is hay that the chimps presumeably have dragged up there themselves. There is also a sign below the tunnel warning people about the dangers of poo from above.
I always find it surprising that more zoos are not using visible tubes, tunnels and passageways for stock.Fun for certain species and fun ffor the visitors too.
Is this the only tunnel leading from the house? It strikes me that this would be an easy place for an individual to be attacked by other members of the troup.