IDK, I think what we call intelligence is actually a large set of different mental abilities, and it's meaningless to lump them all into one number and then compare these numbers.
That's true. I think the vegetarian criterion is mostly "ability to suffer" or something along those lines, but then you still have the issue of animals being raised in captivity and put down humanely. I'm not sure how they tend to respond to that, but I don't think any of us should presume an answer either.
The ability to suffer is why I like using sapient over sentience. Though thats probably due to a few to many arguments where sentience gets used to mean 'ability to discern pain' which some species of tree have been able to show in a very rudimentary form.
IDK = I don't know
Anyway, my point is that human measures of intelligence are utterly inapplicable to animals.
Eh. We have ways of at least attempting to judge animals' ability to be self-aware, solve problems, learn, suffer, and that jazz. Obviously we won't be giving them IQ tests, although some of the great ape language/problem-solving style tests are damn interesting.
Some of the most curious test, that I quite like is the Mirror Test. Though it does have a major weakness in that animals which do not have their primary sense as sight should have a great disadvantage with the test.
Canines for instance fail the mirror test, but there have been some notable dogs, for the lack of a better descriptive word, The dog "Einsteins", that can follow and learn human speech with almost a 400? word vocabulary. Perhaps, if their was a analog test to a difference sense, such as smell perhaps then a canine could past it.
On a tangent note, does any buddy else find it freaken hilarious that human beings have developed to the point, where we can have ernest debates on what foods to eat?
You can look at our evolutionary past in an aspect to obtain food. That from obtaining different foods such as marrow, and cooked meat allowed for brain to proposer and get even more food.