When i read it i think something like a weasel (or of that family), they (and the family) are known for sucking blood from the victims especially poultry during the night and dragging the rest into a large pile because they get so greedy. Usually they won't mess with birds if there are plenty of rats around, but people did mention this was in the desert and and rats may be fairly hard to find. A large poultry house of twenty chickens would be pretty appetizing and the dogs may not have even heard it which is why they didn't bark. They can squeeze through just about anything, hard to keep the little devils out of your chicken coop i hear.
ETA: Now for the Chupacabra myth itself, i occasionally wonder about it. Same as bigfoot, aliens, ghost, etc. About the only one i say does not exist is the lochness.