None.
The Bronx Zoo no longer maintains a walrus exhibit, and to my knowledge there are no current plans to house them in the future.
One individual, not currently listed in Bronx's inventory, may have been very briefly housed at the park alongside Flip in 1910. As it is not known whether he passed just prior to arriving, and considering that at least one source suggests that he was dead on arrival, I have elected to not include him on this page at this time.