Well in the context of evolution, contrasting which species dreams the most is not very informative. The reason I asked is that I have a strange fascination in seeing how an evolutionists without theological faith will bend, guess, and stretch theories into making evolution capable of doing anything. I of course believe evolution occurred but it is certainly not capable of producing biological reality on it's own and a theory that explains everything actually explains nothing.
I can't see how dreams help survival so I was wondering why it has survived and is so prolific.
Well what you seem to be mentioning given your last part about "dreams and survival" talks more to evolution through natural selection rather than evolution itself.
As evolution is the changes in characteristics that occur when they are passed on.
While I could not how dreams help in survival, even if they did not, there would not be any reason for them to be removed from the gene pool for instance if it is in some way related to some gene.
A gene mutation that causes dreams would have neither a positive nor negative impact on the ability of an organism to pass along its genetic material to reproduce another organism. As such it would be a neutral mutation that is preserved even though it does nothing to help or hinder.
I suppose that the best way to look at it, is that evolution does not have a goal, terms like "fittest" "strong" or "weak" are subjective and at times rather misleading in explaining how the evolutionary process works. So people assume that if something is still preserved, then it must have some relation to survival. When it could just be a neutral mutation that is expressed, or it could be tied to something that is needed for survival and continues to exist not because it is useful, but what it is related to is useful. In the case of dreams it would appear to be the brain.