invisible animals???

[teslacoil]

mygaint ground sloths keep disapearing not the female the male some of my other dinos are going as welll and there all the males
why is this happening
and is there any way to fix this because it is getting on my nerves
thanks again
teslacoil

[James]

Is it like this from the start, or do they disappear half way through the game?
I remember some of the downloadable animals didn't show up for me.