Why Should We Not Feed Carnivores To Carnivores

Ever notice when it comes to nature, predators never prey on each other and mainly just on herbivores?
For example:  a Lion kills a Hyena but doesn’t eat it.
Why make it go to waste and not just eat it if starving.
Is it because carnivores taste bad or are there any other reason?

Generally predators tend to avoid other predators to prevent injury as much as possible.
In Ecology, if you’re an injured predator, your chance of survival goes down.
With that, it becomes clear that when predators (especially apex predators and similar) kill each other, they are not in a natural situation anymore.
A predator likely did not mean to kill his opponent to consume its flesh, so he will leave it.
Certainly there are animals that eat their dead opponents, but it seems that as a general rule, large carnivores occupying similar niches don’t see each other as food, so they treat them (or don’t treat them) accordingly.

Nearly any carnivore can be driven to eat other carnivores, but due to herbivore populations being high compared to other carnivore populations which are low and the fact that most herbivores are easier to kill, It is not common, but it does happen for carnivores to prey on other carnivores.

There have been reports of
Coyotes preying on domestic dogs/cats, mustelids, raccoons, oppossums and foxes.
Leopards on hyenas, wild dogs, feral dogs, smaller cats, jackals, mongooses, foxes, civets, cheetahs, lion/tiger cubs and even other leopards.
Wolves often prey on other canid species and young bears.
Cougars feed on wolverines, coyotes, wolves, domestic dogs, smaller cats and bear cubs.
Weasels on shrews and moles in areas where there are no rodents existed.
Bobcats prey on smaller mustelids from weasels to fishers.
Fishers prey on other carnivores.
Canids prey on smaller carnivores as well.
Tigers have been known to included dogs and bears and sometimes feed on leopards.
Male bears are highly cannibalistic and there is a record of a grizzly bear feeding on a wolf carcass.
Lions have been known to take down alligators.
The only carnivores that have not found to be feeding on other carnivores are cheetahs, jaguars, sloth bears and panda bears.

Most reptilian predators however will eat anything that they can overpower, regardless of whether or not it’s a predator or an herbivore.

A summary of an article that I have read:
This article focuses on systems with a top and intermediate predator.
The two prey models showed:
1) Killing the intermediate predator reduces prey vigilance, making them easier for the top predator to kill increasing the top predator population.
2) Killing the intermediate predator increases their vigilance, reducing their hunting efficiency and thus increasing the top predator’s ability to compete.

A graph showed that at low encounter rates between the top and intermediate predator the top predator benefited more from increased intermediate prey vigilance resulting from the remains of the body, versus the benefits of eating the kill.
Basically, leaving the body as an example to the others can outweigh the more obvious benefit of eating it.
Thus it is extremely beneficial for top predators to kill intermediate predators whether or not they eat them, and some factors actually favouring not eating them.
To add to the ideas expressed at the end, leaving carcasses of intermediate predators may also increase the intermediate predators perceived encounter rates with the top predator and the areas which are likely to have top predators present.
Not mentioned is that predators are more likely to carry parasites that can infect other predators

So to draw a conclusion out of this
Generally in any given ecosystem, prey animals outnumber predators, if it was the other way around neither species would survive.
So, it makes more sense to hunt the more available food source.
An example is a forest where unregulated populations decreased thanks to poaching, so tigers began to prey on more bears than ever before because suddenly bears were the more readily available targets.
Obviously predators kill each other to remove competition, and lions rarely eat the hyenas they kill, so generally speaking predator vs predator conflict is based on competition.

What does this all mean and how does this apply to our pets?
Maybe instead of looking at other carnivores (predators) to get our answer as to why we should not be feeding other carnivores to our pets, we should take a slightly more scientific approach to understand why and primarily look in to biomagnification.

Biomagnification, also known as bioamplification or biological magnification, is the increasing concentration of a substance, such as a toxic chemical in the tissues of organisms at successively higher levels in a food chain.

This increase can occur as a result of:
Persistence, where the substance cannot be broken down by environmental processes
Food chain energetics, where the substance’s concentration increases progressively as it moves up a food chain
Low or non-existent rate of internal degradation or excretion of the substance, often due to water-insolubility
Biological magnification often refers to the process whereby certain substances such as pesticides or heavy metals work their way into lakes, rivers and the ocean, and then move up the food chain in progressively greater concentrations as they are incorporated into the diet of aquatic organisms such as zooplankton, which in turn is eaten by fish, which then may be eaten by a bigger fish, or large birds or animals or humans.
The substances become increasingly concentrated in tissues or internal organs as they move up the chain.
Bioaccumulants are substances that increase in concentration in living organisms as they take in contaminated air, water, or food because the substances are very slowly metabolized or excreted.

Although sometimes used interchangeably with “bioaccumulation”, an important distinction is drawn between the two, and with bioconcentration.

  • Bioaccumulation occurs within a trophic level, and is the increase in the concentration of a substance in certain tissues of organisms’ bodies due to absorption from food and the environment.
  • Bioconcentration is defined as occurring when uptake from the water is greater than excretion.

Thus, bioconcentration and bioaccumulation occur within an organism, and biomagnification occurs across trophic (food chain) levels.
Lipid, (lipophilic) or fat soluble substances cannot be diluted, broken down, or excreted in urine, a water-based medium, so they accumulate in fatty tissues of an organism if the organism lacks enzymes to degrade them.
When eaten by another organism, fats are absorbed in the gut, carrying the substance, which then accumulates in the fats of the predator.
Since at each level of the food chain there is a lot of energy loss, a predator must consume many prey, including all of their lipophilic substances.

For example:
Even though mercury is only present in small amounts in seawater, it is absorbed by algae (generally as methyl mercury).
It is efficiently absorbed, but only very slowly excreted by organisms.
Bioaccumulation and bioconcentration result in build-up in the adipose tissue of successive trophic levels.
Anything which eats these fish also consumes the higher level of mercury the fish have accumulated. This process explains why predatory fish such as swordfish and sharks or birds like osprey and eagles have higher concentrations of mercury in their tissue than could be accounted for by direct exposure alone.

Example, herring contains mercury at approximately 0.01 parts per million (ppm) and shark contains mercury at greater than 1 ppm.
DDT is thought to biomagnify and biomagnification is one of the most significant reasons it was deemed harmful to the environment by the EPA and other organizations.
DDT is stored in the fat of animals and takes many years to break down, and as the fat is consumed by predators, the amounts of DDT biomagnify.
DDT is now a banned substance in many parts of the world

Substances that biomagnify
There are two main groups of substances that biomagnify.
Both are lipophilic and not easily degraded.
Novel organic substances are not easily degraded because organisms lack previous exposure and have thus not evolved specific detoxification and excretion mechanisms, as there has been no selection pressure from them.
These substances are consequently known as “persistent organic pollutants” or POPs.
Metals are not degradable because they are elements.
Organisms, particularly those subject to naturally high levels of exposure to metals, have mechanisms to sequester and excrete metals.
Problems arise when organisms are exposed to higher concentrations than usual, which they cannot excrete rapidly enough to prevent damage.
Some persistent heavy metals are especially dangerous and harmful to the organism’s reproductive system. (source: Biomagnification Wikipedia)

Now to simplify all the above:
Let’s have a look at the food chain:
1) Plants are at the very bottom of the food chain.
Plants absorb water and nutrients from the soil, along with the toxins and get their energy from the sun, which, for the most part, is inexhaustible.
They then use this energy for their own growth and maintenance.
2) The plants then get eaten by Herbivores (like rabbits, cows deer etc), consume the plants (which they will need to eat a lot to live), which means that there is an energy loss between the sun and the consumers and any contaminates have had a chance to accumulate/ build up in their body.
3) Carnivores like wolf’s foxes, bears, crocodiles then show up and eat the herbivores.
This results in an even larger energy loss and they in turn will have an even bigger build up of contaminants.

As a carnivore is the highest up the chain it would have a higher level of heavy metals, radioactive isotopes, and carcinogenic compounds compared to the herbivores.
These can’t even be destroyed or removed by cooking, never mind when being eaten raw.

In short:
The higher you go up in the food chain, the more you’ll have to eat from the level below, and thus the concentration of these toxins increases as you go up.
Add to this that carnivores probably carry a higher amount of parasites which can be shared among other carnivores.

Somehow wild animals know this instinctively and therefore it is rare for a carnivore to eat a carnivore.
Or as explained previously is it more to do with setting an example for others not to cross paths by leaving the dead bodies of others?

Who knows: but whichever the case, we’ve got science they’ve got the rules of nature.

There is a grey area when it comes to some reptiles.
Crocodile meat is often readily available and consumed by humans and their meat is classed as a white meat, so obviously people raise the question can I feed my pet carnivore Crocodile meat?
To keep it short: Knowing the above it is not something I would recommend or feed my pets

Feeding reptiles or other species that feed off insects (insectivores) are perfectly fine to feed as most insects will have fed off plants and or other insects, which are not high enough in the food chain to cause any concerns.

What about omnivores?
Omnivores eat meat.
Yes it is true that omnivores occasionally eat meat, but meat is not their only food source.
For example: some poultry or wild game birds will eat insects or sometimes each other, but their primary food source is vegetables, grains and seeds.

What about pork?
I’ve heard or read somewhere that dogs cannot digest pork and it isn’t good for them?
I am fully aware that pigs will eat meat when they get the chance to do so, but they also eat vegetables and plants (they are basically walking waste disposals).
Again: Biomagnification is not a big problem, as meat isn’t their  primary nor only food source.

I’m not quite sure where the myth comes from that dogs cannot digest pork.
The only thing I can think of and will have to agree with is that pork is quite rich and not always tolerated well.
I only have to look at myself as I’ve got intolerance to pork, resulting in stomach upset and itching, yet our dogs love it and get pork roughly twice a week in the shape of a pig’s foot with some meat of a different protein source, or pork mince with a different protein source.

As with every other protein source when introduces the first time, building it up slow is key so add a little but more each time you feed it starting with roughly 10% to 20% and build up from there.
You will soon find out if your pet tolerates pork or not.

So all in all the conclusion is that it is perfectly safe to feed omnivores and insectivores to your carnivore.