Lipids would be the answer that you are looking for. When talking food energy it's best to speak in terms of calories. Therefore, lipids or fats offer the greatest amount of heat or energy.
Sleeping on the stomach is "prone," on the back its "supine."
Habitat destruction is the key one out of all of these. Animals being kept at the zoo for research are usually endangered or vulnerable species which is doing more good than harm to them. Legal hunting of animals is most likely for rabbits, deer, and a stabilized population in the wild. Habitat destruction can destroy many populations and cause loads of damage. An example of that would be the Australian wildfires at the start of 2020.
