We all take the same photos in the same places! In this case between the bars of the wooden fence of the Kudu's enclosure. Unlike you I have never NOT seen the Kudu- including the male- in their outdoor area.
But on my last visit there I saw no Bongos at either Howletts or Port Lympne- I couldn't figure out where they were either as the enclosures were still labelled 'Bongo' but there was no sign of them..
