Clearly, creatures such as us humans, after vastly increasing the entropy of our food, expel most of the mass that we consume. 

Some creatures, however, do NOT get the opportunity to eat nearly as often, even though these creatures are if anything more competitive (and perhaps cannibalistic!) than we are - snakes come to mind here, as do spiders.  

So the awkward question that arises is thus: do such animals have a higher "absorption rate", if you will, then humans and other frequent feeders?

In other words, do such animals maximize their diet by incorporating more of the mass of their food and expelling less of it, or is there some physics/chemistry which makes this difficult?


Thanks!