Thanks, looking forward the new sequencer 
Our pack comes with the rigged stylized mesh and rigged realistic mesh will follow soon for all the animals. If you would want to apply them to your own rig, it’s doable right in UE via retargeting (https://docs.unrealengine.com/latest/INT/Engine/Animation/RetargetingDifferentSkeletons/index.html).
If you will try to retarget the animations to a similar body shape it could work, but depends on the differences in the skeleton structure and proportions. There will be certain range of differences that will work, but after certain point it probably won’t look too good.
With model nothing like the one from animations it could work, but probably will look bad.
Then there is also a big difference between the animals and the way they move, how they use their limbs in the locomotion and lot of other things, so retargeting buffalo to a bear probably won’t look too good and absolutely not realistically. But I guess all that also depends on what you are willing to tolerate in your project.