Animal records are not able to be merged due to the complexity in the intake and outcome events. If you have duplicate records for the same animal, you'll want to manually copy over any information you'd like retained on the remaining record, then you can then delete the duplicate animal from Record Management yourself (see this article here: How do I delete an animal?).
If you prefer not to delete one of the duplicates (since each record has separate intake and outcome information), on each one, you can reference the other record's ID number in a pop-up memo. This will make it clear to anyone accessing these records that there is additional data in another record.
Please note, if you delete the transferred record, then it will remain as a pending transfer (red numbered notification on your partner tab). Ideally, you should delete the record you created unless it has additional events like an adoption that is tied to a transaction, or a signed contract, then you might instead want to keep both records and use a pop-up memo.
Alternatively, you could also delete the transferred record and leave it in your pending transfers.