Which theory is the true one?, About chupacabra.Puerto Rico

Last night I was watching a show on Discovery Chanel and it was about Chupacabra. The guy who did the show had few theories on what they are and where did they come from. I thought it was pretty interesting. I was wandering what everybody else thinks about them.
Here they are.
1/ They first appeared in Puerto Rico when there were lots of UFO sightings and some people claim they have actually seen them being left behind when mother ship took off. There is no evidence to support this but why not, I say. The only thing that doesn't make sense is - in less then 12 months Chupacabras have been seen in Mexico and even as far as North America. And there were 1000s of reports. Some of them happened in the same day but 100s of miles away. How many of them were left behind then?

2/ There are portals to other dimensions all over the world and some of those places are thought of as "cursed" and it goes back to 1000s of years ago. Anyway, this guy thinks that maybe all these creatures (even Big foot) live there and they come to visit.
The jungle in Puerto Rico where most of the sightings have happened has been "cursed" and people go missing all the time. Could they have found the portal or are they just hopeless at reading maps. ? Once again, there is no proof to this theory.

3/ Chupacabras are mutated insects. Apparently they sort of look like giant mosquitoes and as they originally came from such a deep unexplored jungle, could it be possible that they lived there for years without being discovered? But I don't understand, how come they only started coming out few years ago? Where were they until then? Did they all of a sudden develop the taste for sheep and other domestic animals?

4/ In Puerto Rico US government has labs and they don't need approval to conduct any sort of experiment. So after the WWI they started developing this creature which they were going to use in wars. It was said that this creature would suck blood out of the enemy soldiers. There are even some stories from WWII. Japanese soldiers used to find their men with not even one drop of blood left in them and only a small scar. What happened to them? No one can tell for sure.
Anyway, apparently later on CIA lost control over those creatures and some of them escaped into the jungle.
Lots of Puerto Ricans believe this story because it is a proven fact that CIA did do all sorts of experiments over there because they weren't allowed to do them in America.

So what is your opinion? I'd go with 4. I mean, why not? Why couldn't people make a new creature? That is possible, right?