"Lo, though nature red in tooth and claw..."

-Alfred Lord Tennyson, 1850

We often classify animals according to what they eat, as a sort of shorthand for describing what kind of animal they are. The three basic classifications we use are herbivore (plant eating), carnivore (meat eating), and omnivore (will eat both plants and meats). With each category are sub-categories that are more specific: for example, within the herbivore category are the frugivores, which eat only fruit, and folivores, which eat only leaves (not grasses). Within the carnivore section are various levels of meat-eating. Animals which need meat in order to survive, but can also consume plant matter (although they get very little nutrients from it) are called obligate carnivores. Animals that can *only* consume meat are called hypercarnivores. Interestingly, the hypercarnivore classification does not include most of the major predatory animals – hypercarnivores are usually birds of prey and water-dwelling species, such as certain fish, snakes, dolphins, and octopi.

The last category is the broadest, and the one to which man belongs: omnivores. Many people mistakenly think that omnivore means that the animal will eat anything. But what it really means is that the animal is capable of extracting nutrition from both plant and animal matter. A common example of an omnivore would be the raccoon. Raccoons are very successful at adapting to living with humans, in part because they can adapt to eating human foods – more specifically, in urban areas they usually eat trash and/or pet food. But in areas away from humans, raccoons can be very picky about their diet. They will catch and eat small fish and frogs, and the also like to eat insects, worms, and snails. All these are a form of meat. Raccoons also eat plants, roots, seeds and fruit, which are all plant matter. But other omnivores are not so wide-ranging in their abilities to extract nutrients from different sources. Humans, for example, do very poorly at extracting anything useful from cellulose plant material, like bark, wood, and grass. We also do not get very much nutritional value from eating insects. So being omnivorous does not mean that an animal can survive on a diet of anything – it just means that the animal is capable digesting both meat and plants, to a greater or lesser degree.

There is very frequently overlap between the carnivore and omnivore category. Bears are a particular problem. Technically they belong to the order Carnivora, but they are largely omnivorous. The polar bear and the sloth bear (which eats only termites) are two true obligate carnivores in the bear family. But, due to details of their teeth and their ancestry, bears remain in the carnivore category in terms of their taxonomy, but are considered omnivorous in the common sense of the word. In the same vein, squirrels, which we think of as primarily eating fruit, seeds, and vegetables, also eat bird eggs (considered meat), bird fledglings, insects, and sometimes small reptiles. So while they technically fall into the herbivore category, their actual eating habits are omnivorous.

We can see that these three categories are flexible in the common usage. In taxonomic usage, they refer not only to what the animal has been observed eating, but to internal organs, skeletal and tooth structure, and ancestry. This can be confusing to the non-scientist, but neither usage is ‘wrong’. The ‘correct’ assignment of an animal to a particular category depends on the context, and for most people the context is not a strictly science-based one. Therefore, in common usage it is not incorrect to say that bears are omnivores, or that squirrels are herbivores.

The question that plagues many humans is, are humans omnivores or herbivores? The scientific answer, based on dentition and internal structures, is that humans are omnivores. But remember that omnivorous does not mean ‘will eat anything’. Omnivores are capable of digesting plant material and meat. But that doesn’t mean that they need both plant and animal matter in their diet. Many omnivores eat a mostly plant-based diet, while many lean more towards the carnivorous side. Many have diets that change according to the season, or their location. Humans, as omnivores, can choose if they want to eat a plant-based diet, a meat-based diet, or something in between. The omnivore category does not limit us in terms of diet - it gives us the broadest possible choice.



  1. Katy M Said,

    I didn't know that humans couldn't extract much value from insects! So people who eat grubs are doing it for . . . taste, rather than nutrition? Or what?

    Posted on June 4, 2009 at 8:50 PM

  2. MaryEllen Said,

    Grubs (larvae) have more nutrition than adult insects (an insects' exoskeleton is made of chitin, which humans can't digest), but humans have to eat *a lot* of grubs to get any real value. People who have nothing else to eat, eat grubs, and people who want to impress/shock/gross out other people eat them.

    Posted on June 4, 2009 at 8:58 PM

  3. Question, though it may not be quite in you purview. Most every time I plant something- flowering plant, shrub and most recently lilacs- something comes along and digs. I'm not sure what, most likely a raccoon but possibly a skunk or possibly a raccoon. How come human scent doesn't put the digger off?

    Posted on June 5, 2009 at 5:23 AM

  4. MaryEllen Said,

    Skunks and raccoons both are very easily habituated to humans - they live very comfortably in suburban and urban areas and easily get used to scents, sounds, and visuals of human habitation. There are several things you can try - when you plant something new, put a tube of fine mesh or chicken wire around the edges of the hole, so the animals can't get to the roots. also, I have found that spraying synthetic predator urine (coyote is very common, easy to find in gardening stores) in a circle on top of the soil around new plantings often discourages digging. I'm told that cayenne pepper also works - anything that makes the soil smell or taste nasty, but isn't poisonous to the plants or animals.

    Posted on June 5, 2009 at 12:27 PM

  5. Phyl Said,

    If it's possibly squirrels (as I've experienced with big potted plants on balconies and patios), you can also sprinkle blood meal lightly on the soil around the plant. The main problem is that it soaks into the soil after a soaking, and the squirrels come back, and you shouldn't keep slathering the blood meal on.

    So I think MaryEllen's suggestion about the mesh is best. You'd need to weigh it down or anchor it somehow, though, so the digger wouldn't just flip up an edge and keep digging.

    Posted on June 25, 2009 at 6:05 AM

  6. MaryEllen Said,

    Good suggestion, Phyl! I wasn't clear about the wire mesh thing - it should be a tube-shaped thing, perpendicular to the ground, and partially buried - basically, when you dig the hole for the planting, line the edges of the hole with the wire mesh, and leave it sticking up some at the top to prevent climb-overs. The animals are being attracted to the disturbed soil, so if you can surround that with a 'fence', both underground and above, it may discourage them. Then once the soil has settled, you can just snip off the part of the mesh that is above-ground, so you don't have ugly mesh in your yard.

    Posted on June 25, 2009 at 11:39 AM


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