you would know if you feel a connection, or relatability of being an animal (inner) or being an animal (past). If you don't feel like an animal (in the past or present), then no. I'm not completely sure though..

if u become one ill add u to my list

It can range from having full memories of hunting, running with a pack, explicit details of a specific environment, to phantom limbs like tails and ears, claws and sharp fangs.

Identifying it is more of just like.. looking at how connected you feel and how strongly you identify with that animal and deciding if it's just the appeal or if you fully believe or feel that you are that animal. Mine is psychological, I grew up adoring cats and pretending to be a cat, searching cat behaviors, my whole thing was cats. Being older now I look back on that and think it's funny, because I still do SO much of that subconsciously. and it is soooo much deeper than just liking cats and thinking they're cute. For me its phantom limbs, teeth, when I run out of things to say to people I meow like genuinely I do that ALL the time.