I was there last Wednesday and the keeper at the talk said that they were an all female group.
As mentioned in my earlier post, the 2013 European Hippo Studbook lists eight female hippos at West Midlands Safari Park as at 31st December 2012. (And no males are listed as being present.)
Confusingly, looking into this in a little more detail, four of these hippos, although listed as females, have masculine names:- “Augustus”, “Hugo”, “Howard” and “Geoffrey”.
Checking back through earlier editions of the studbook, these four animals are listed as males in the 2007 studbook but are then listed as females in the 2008 edition and all subsequent editions!