Indeed, as others have pointed out, this photograph was taken just before 5:00pm; the other photo that I uploaded recently of the young Malayan tapir at London Zoo was also taken at about the same time.
On my last visit to the zoo both the female and her calf were very active and clearly visible in the late afternoon; this is generally the best time to see them. (Frustratingly, though, despite several visits to the zoo during the summer months I never saw the youngster whilst it still had its juvenile spotted colouration.)
Agreed, it is all down to timing; it just depends if you’re lucky enough to be in the right place at the right time.
Of course the tapirs can be seen at other times of the day but, generally speaking, I’ve found the late afternoon to be the time when they’re most likely to be active.