Why are you surprised? Different animals are at different levels of evolution, therefore their energy processing cycles will vary accordingly both during the day and night...
Also, studying sleep is a much different type of work since the body is at rest and what actually changes the most are the EM waves in the brain! Meaning that it is more applicable for someone who can clearly understands waves vs. a biologist, for example...
In addition, since studying sleep in detail requires proximity brain sensors, it is still a very difficult and cumbersome process! A better process would be to measure the energy from a certain distance, but, of course, our tools and instruments still cannot do that at this present time! However, if/when that can be achieved, then we also have the serious and controversial issue of direct brain manipulation!!!
-wirelessguru1
