First of all, the translation is incorrect, again.

"Amelyik" is "the one that/which".

"Ami" is "what" or "such a thing that". Something like that.

So,

"Arról mászunk le, aminél állatok sétálnak." - means that if we encounter something, anything, with animals walking in front of it, we will climb off it.

And

"Arról mászunk le, amelyiknél állatok sétálnak." - means that we will climb off the one, that one, in front of which you see the animals walking.