Here is UPS rules from there web site.
(n) UPS does not regularly provide service for packages containing live animals. UPS will only accept live animal shipments on an exception basis. Transportation for packages containing live animals is limited, must be prearranged, and as with all other packages, will be provided only according to the terms and conditions contained in the UPS Tariff.
So unless prior arangements are made they do not except live animals. So some of the bigger sellers can use it, but most smaller breeders are out of luck.