Ok, I have a theory on this, but I don't know how accurate my thinking is on this, so please don't apply this idea as absolute truth...
I mean, I can see no other way that it can be, maybe I'm just afraid to admit to myself that these are what the scriptures are saying to me.
You have the ability to think and reason for yourself, as well as I do, so I'll be interested to hear your thoughts on these scriptures...
Ok, first of all, if we go outside of humans, along with animals of every shape and size, we also have to consider every living thing of every shape and size- this would include plants, bugs, even germs. Scientists did an experiment, they put one plant in one room, and the same kind of plant in another room. To one they played soft instrumental music, and spoke to it cheerfully and kindly, and it thrived. To the other plant they played loud heavy medal music and spoke to it rashly, it withered and died. This reminds me of the verse (I think it is in Proverbs) "Sweet words are like honeycomb- soothing to the soul and health to the bones."- which has also been proven scientifically that terminal patients who keep a good and cheerful attitude have a much better survival rate then those who don't.
We know that God told us to consider the way of the ant, and what do ants do? They lift many times their own weight, are always busy, and they leave a trail for other ants to follow. Like He said to us, each of us should carry our own load and help others carry theirs. And that we should follow Christ- like my avatar picture, when we follow Christ (not man made doctrine) we form a line like ants following the Leader.
We know that the devil was speaking through the snake to Adam and Eve, and got in trouble for that. We know that God sent plagues to Pharaoh of flies, locusts, frogs, etc. ok, there is a verse I can't find, but I know it's in the Old Testament. God was speaking about a bug, I think it was a spider, but I can't remember for sure. And I can't remember the exact wording, but what God was saying is that they work for Him.
In Revelation 8 it speaks of a great star that came to the earth named "Wormwood" and it came to destroy. Also, Genesis 9:5 says that both human and animal will have to give an account for spilling human blood/taking human life.
Now both angels and demons work for God- demons tempt us to sin against God, and God allows this because He wants us to be tried and tested. And we know the verse that all angels are ministering spirits to those who will inherit heaven. Now God told us to preach the gospel to every creature, but this does not mean animals- can you imagine baptizing an ant, or a germ? They are not able to communicate to us that they believe that Jesus is the Son of the Living God, or to make a lifetime commitment to serving Him. So we know He meant every creature made in His image (human).
So this is what I think... I think that angels can take on the form of both humans, animals, even as small as bacteria (there are good and bad bacteria, the good bacteria we cannot survive without). And that demons can go in pigs, we know they have been in humans in the form of demon possession (which I don't believe happens anymore), but I do believe demons go into humans in the forms of germs and bacteria, and that they fight against the angels in the same forms. God punishes sin with disease, even today. And as the Christian prays, praises God, and has faith, that the demons leave and the person heals. Because demons don't want to be around what is holy and clean.
Beelzebub was a big golden fly, and was worshipped for the power to bring disease and kill.
So to answer the question if animals have eternal life, it's both yes and no- depending on if they are an angel or a demon. But I do not believe animals have souls like a human, we are made in God's image, unlike the angel or the demon.
Ok, I know it's out there, but I can't see any other way that it could be with considering all scriptures.