The white rhinoceros consists of two subspecies, the southern white rhino, which is relatively common, and the northern white rhino, which is critically endangered and is thought to be extinct in the wild due to poaching, habitat loss and ongoing conflict in its central African habitat. I actually have some stamps of the northern white rhino on a postcard from Côte d'Ivoire from a while back.
My mum reported that she did indeed see white rhinos on her safari, but missed out on snagging the "Big Five" during her safari due to overly-elusive leopards. Thanks again for the card!
Stamp commemorating Botswana's 2011 census. As you can see, Botswana's population has nearly tripled since the first census in 1964, and it has one of the youngest populations in Africa, with a median age of just 21!