I thought it was only moles that are naturally hemophiliac which is why a thorny stem in their hill would be enough to kill them.

The only reason I have been told not to put a wheel in a Gerbils cage is that they can actually run themselves to death on it. Silly animals don't have the intelligence to side step to get off it, they instinctively try to outrun it instead.

Hamsters: Great on toast with a splash of Lee&Perrins