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While I know that in nature, carnivorous animals are poorly suited to eat plants (largely due to having sharp teeth, not grinding teeth, as far as I know), I was wondering if, in an emergency situation such as imminent starvation, could a carnivorous animal such as a wolf survive solely on plant life, maybe requiring it to be ground up before hand? Could an herbivore survive on meat, if the meat was prepared in a manner that would allow the herbivore to eat it? Would a wild animal voluntarily consume food that it is not suited for if it would stave off certain death, or would it require force feeding or training?

Also, I am interested in the other side of this question: if an animal cannot safely consume food outside of its normal diet (carnivore eating plants, herbivores consuming meat), what negative effects would this action have on the animal?

Just a note, this is purely a hypothetical question, and I am only asking out of curiosity. I am in no way planning on doing this, nor do I advise anyone else doing this if there is a high chance of it harming the animal.

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    $\begingroup$ Yes we are omnivores, but before hominid specie developed the capacity to cook meat the meat was eaten raw, and before they had the capacity to come up with ideas - like tools for hunting they ate a plant based diet. I agree with the fact that we are omnivores now, thousands of years later, after all the mutations in our body took place, but we do tend to fall into the herbivorous part of omnivores, so our diet should be 80% plants - 20% meat. Anything more than that puts us at risk for developing arterosclerosis. And dont even get me started on the fact that people consume way to much animal $\endgroup$ – Renee Nicole May 27 '17 at 3:37
  • $\begingroup$ What do you mean by a "diet contradicts an animal's biology"? Contradiction is the logical opposition of two facts, e.g., "it is day" and "it is night" contradict each other. But I find it meaningless to talk about a diet (which is a list of food) contradicting a "biology" where you probably meant "physiology" and which is the dynamical system consisting of a single living individual (the cat or human) in your example. Note that "herbivore", "omnivore" and "carnivore" are human constructs, just as the classification of living beings into "species", neither represents a airtight category presen $\endgroup$ – Oskar Limka Jun 15 '18 at 10:22
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This is kind of a weird/trick question. How long do you want the animal to live? If the lifespan is shortened or compromised does that fit.... Obligate carnivores (cats, dogs) do eat plant material. In the wild cats mainly eat grass to get rid of hairballs. Cats are more impacted by phytotoxins than dogs. However, both, are extremely vulnerable to compounds that don't bother humans (xanthines like theobromine, caffine, compounds in garlic, onions, broccoli, mushrooms). Cats can't convert plant fats into what they need (we can) as a result they can go blind if they don't get the animal fats they need. Likewise, herbivores will suffer increased cancer, heart disease, renal failure from diets with animal fats / protein. Your mention of "wolf" is interesting because there is a South American wolf that supplements its diet with a tomato relative (called something like "fruit for wolves" in Spanish). This is probably only "good" for it in that it keeps the wolf from otherwise starving. I don't know that it has a strong deleterious effect (probably not, but it could be more sensitive to trace alkaloids in the fruit) but it could hurt it in a minor way.

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    $\begingroup$ Hi! Welcome to the site. It would improve your answer if you add some references for the information you provide. $\endgroup$ – biogirl Mar 20 '14 at 3:18
  • $\begingroup$ "fruit for wolves": en.wikipedia.org/wiki/Solanum_lycocarpum $\endgroup$ – Dan S Mar 26 '14 at 21:46
  • $\begingroup$ unable to synthesize taurine from other sources (as herbavores and omnivores can) "For instance, cats require that their protein needs be met primarily by animal rather than plant sources, especially to supply adequate taurine, an amino acid which cats do not synthesize well for themselves." felineconstipation.org/prevention.html $\endgroup$ – Dan S Mar 26 '14 at 21:50
  • $\begingroup$ let me know what exactly you want references for. I was not directly quoting anything from any peer reviewed pub if that's what you want $\endgroup$ – Dan S Mar 26 '14 at 21:54
  • $\begingroup$ Hi! It's not necessary to include references from peer reviewed research papers if your references are "reliable" $\endgroup$ – biogirl Mar 27 '14 at 1:57
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I think that the distinction between carnivores and herbivores contains a gray area with a spectrum of omnivores in-between. Bears are placed in the order of carnivores, but are definitely truly omnivores see link. However, if you give them a choice between a salmon and blueberries, it's quite clear what will be devoured first. That's why it's a carnivore. The answer by @Dan S clearly shows that not all creatures may be in the spectrum. For example, domestic cats are indeed quite carnivorous and would not touch plant material. On the other hand, now we are talking pets (the SE where this question apparently came from) - dogs are truly omnivores despite being categorized as carnivorous.

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I'm pretty sure humans are herbivores, and we've been doing fine on meat. Not as fine as we could without meat. There are just extra illnesses to watch out for like what was listed above: heart disease, kidney failure, cancer, strokes. These illnesses could occur on a natural diet as well, so if there are already precautions in place for these things, the animal should still live a happy life (maybe cut short by some years).

Animals eating diets that aren't suited for them is not as rare as you might think. As I stated above, it seems likely that the natural diet for humans is (or at one point was) herbivorous. We have had several mutations over the years that have assisted us in being able to eat meat with less adverse effects: http://www.wsj.com/articles/SB10001424052702303933704577533271378820202. So, admittedly, giving primates meat is probably worse than giving humans meat. But at one point humans were eating meat without those mutations, and the human race still managed to survive.

We also tend to feed domesticated carnivores, such as cats, grains. Cat genetics has not been studied as much as human genetics, so it is not certain whether cats have also evolved to better be able to handle a diet that is contradictory to their nature. However, either way, a species going against its natural diet seems to be able to sustain a reasonable, though perhaps not optimal, life.

The situation may be different if a species was subsisting solely on a diet that is contradictory to its nature. However, it has been done. There are reportedly human communities (such as possibly the Inuit) who survive or have survived on meat-only diets: http://www.popsci.com/science/article/2011-04/fyi-what-would-happen-if-i-ate-nothing-meat. Many people who feed their cats a vegan diet, with supplemented vitamins, report that their cats live longer.

If giving an animal food that contradicts their biology, it is important to alter in some way. Humans face a high risk of contracting a food-borne illness if meat is not cooked properly, and grains in cat food are ground and mixed with the food. If giving an animal only food that contradicts their biology, the food should be supplemented. Cats can go blind without taurine, which is an amino acid that is created by animals and not plants. Humans on a meat-only diet could get scurvy from lack of vitamin C (if eating cooked meat) and constipation from lack of fiber.

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    $\begingroup$ You may be sure, but you're still wrong :-) Humans, like bears & wolves (and chimpanzees!), are omnivores, with the amount of meat in their diet varying by biology & opportunity. Humans who eat a (non-supplemented) exclusively vegetarian diet can experience various nutrional deficiencies, just as those who eat an exclusively meat-based diet do. $\endgroup$ – jamesqf Jan 28 '17 at 21:17
  • $\begingroup$ Sure you maybe, but wrong you are. Humans are not herbivores. Humans are omnivores. We are descended for apes that had begun the evolution towards eating meat... cooked meat and cooked vegetables. It should be remembered that cooking was not invented by humans nor was mastery of fire or even stone tools. These were things our species grew up with. We are descended from a hominid species that had already mastered the three. $\endgroup$ – JayCkat Jan 29 '17 at 4:22

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