In my opinion they are on the small side, but they were heavily stocked either. From another thread I was told that Blackbrook are intending to reduce the number of species and maybe open up the pens.
Other mammals include several species of tamarin and marmoset, meerkat, short-clawed otter and muntjac (nothing particularly amazing; birds are their big thing). There were plans to add red river hog, but I'm not sure whether they have followed through.