He's one of the oldest in Europe so i imagine it's just a lot of grey hairs. The video footage of him shows him to be very very grey so I don't think it's just this photo
Nico is indeed almost white on his back and thighs, but its just very silvery hair, not unusual colouration. He is now the oldest male in Europe.
When this pair went to Bristol Zoo one winter I had the chance to see them close to- even then Nico was very silvery and rather shaggy-looking on the shoulders etc.
They tried to breed from them. During one winter season, they were sent to Bristol and each was put with one (or more) of Bristol's Gorillas but nothing happened. They didn't really give them long enough though Nico proved aggressive so they soon sent him back. Samba stayed longer but nothing happened.
