An embodiment of a card holder system for retaining a card with an animal cage can comprise a card holder designed and dimensioned to selectively retain the card, and a retention member adapted for retaining the card holder to the cage. The retention member is adapted to be secured to a side wall of the cage. In certain embodiments, the card holder can be selectively retained in one of a horizontal orientation and a vertical orientation. The card holder system can further comprise an adapter member, the adapter member being designed and dimensioned to be coupled with the card holder such that the card holder may be selectively positioned in one of a first orientation and a second orientation, the second orientation being substantially rotated ninety-degrees from the first position.