They do seem to adapt with minimal trauma. Usually.
Not-so with horses, I gather.
Heard today a horrific tale of a pair, a very old horse plus a younger one: pasture mates for some few years.
Then the young owner of the younger horse one day brought in a trailer and loaded her horse.
The commotion, frantic neighing/body language of both: needed no human words to comprehend.
Even out-of-sight as the trailer disappeared: it could be Heard.
Such an ugly scene to contemplate..Humans can be such nasty Me-Me-Me oblivious Bastards!
(For whatever combination of 'reasons', the elder was killed shortly thereafter;
unclear to what extent 'compassion' was involved in that decision--given the general attitude of "ITs" 'owner'.)
Fortunately I heard not.. of the psyche of the younger horse, taken away by its owner--of whatever %sentience.
Some cats--normally solitary hunters--clearly bond in similar fashion/suffer quite as evidently, when separated;
some %unknown of humans have been known to relent in such cases. Others, as we know, Care-not or ... See-not.
Glad yours stayed together. Good job.