Why Do Animals Eat Their Prey Alive?

lion stalking prey before eating it alive

It’s a dog eat dog world out there.

It’s also a lion eat antelope, snake eat mouse, frog eat fly… you get the idea. 

Many species deploy a range of tactics to successfully kill prey prior to consumption.

A cocktail of venom, sharp canines, hidden trapdoors and grasping talons are all physiological characteristics that help immobilize prey.

However, some animals take things one step further, striking fast and consuming their prey as quickly as possible, often while it is still breathing.  

But why do some animals eat their prey alive?

Several species eat their prey live for different reasons including trying to eat as much of their prey as possible before larger predators steal the kill, preventing the build up of toxic bacteria or simply because their powerful jaws leave no reason to wait. 

There really isn’t any one particular right answer for this. In fact, all these reasons, and more, are valid.

We’ll be exploring the fascinating, albeit brutal, world of just why animals eat their prey alive.

Reason 1: Replenishment Of Lost Energy

This seems like an odd one, right? After all, eating prey, regardless if it is alive or not, will still give you precious energy.

However, some species need an immediate pick me up.

Reproduction, for example, is incredibly energetically costly. But what does this mean?

Across taxa, there are certain costs associated with reproduction. This is especially true for insects. Especially female insects.

A certain amount of energy must go into mate selection and courtship, the production of sex cells, or gametes, and the direct laying of eggs.

Some males present packages of protein, in the form of spermatophores, in which a female can snack on during the mating process to keep her distracted and well-nourished.

But what if males are unable to produce spermatophores?

Well, he becomes the snack.

This is known as sexual cannibalization – the process whereby one mate, usually the female, consumes her sexual partner before, during or after copulation.

In fact, sexual cannibalization is a common phenomenon in species such as spiders, scorpions and mantises. Thankfully, this practice is not common in mammalian species. For now.

By consuming her male conspecific, a female gains an immediate energy advantage, providing enough nutrients to support a developing clutch of eggs. It may even help support a larger clutch of eggs.

The process isn’t as swift as you expect, or what the male would ideally like. Rather than consuming her male victim’s head in one fluid bite, the female chops down, tearing little bites out of her still living sexual partner. 

But fear not for the male, he is adapted for this grisly eventuality. Unlike many mammals, whereby decapitation will likely end it all, the mating behaviors of male mantids are controlled by a network of sophisticated nerve tissue found in the abdomen; not the brain!

It’s a win-win situation for all. The female can happily eat her male prey whilst still alive, providing vital nutrients and energy for the development of her offspring, while the male passes on his genes to the next generation – even if he doesn’t survive to see his offspring reach maturity. Meh, c’est la vie.

Reason 2: To Avoid Kleptoparasites 

Kleptoparasite – what an unnecessarily sciency word. 

But what is a kleptoparasite?

Kleptoparasitism is a feeding behavior, whereby one animal purposefully steals food from another animal. 

And why not? Why go to all that effort to track, hunt and kill your prey, when you can just steal it from someone else? 

In response to this, many predators will often try to eat as much of their prey as possible, before kleptoparasites, or any larger predator for that matter, attempts to steal it away. 

This often means whilst the prey is still alive.

Besides, hunting is noisy and causes quite the commotion. Social predators, such as African wild dogs, often communicate using a series of vocalizations. Any larger predator or kleptoparasite in the vicinity will be aware of a potential hunt underway and will try to stay as close as possible to the scene. 

After a kill, the scent of blood will also attract other predators and kleptoparasites. 

African wild dogs are a medium sized canid species, native to the African continent. They hunt in packs, chasing their prey to exhaustion. When their target can no longer sustain running, the wild dogs take turns biting and tearing flesh off its prey. 

It’s a technique that has gained them quite a nasty reputation. But hey, that’s what nature is all about. Adapt and survive. 

Afterall, the process of running prey to exhaustion is equally as energy costly to the wild dogs. So, if this method of hunting allows the wild dogs to eat as much of their prey before it gets stolen, then good for them. 

Reason 3: Reduce The Likelihood Of Getting Sick 

Bacteria love nothing more than a rotten carcass. Especially one that has been festering in the sun for many days. 

Raw meat is a hub of microscopic activity. A wealth of pathogenic microorganisms can be found naturally in raw meat, but can multiply exponentially in dead animals, as immune systems cease to exist.

Animals with a keen sense of smell are able to distinguish between fresh and rotten meat

But for those animals that may not have their olfactory senses up to speed, how do they differentiate between a recently killed carcass, to one that has been decaying in the blistering sun, teeming with bacteria and diseases?

Well, many species just don’t take the risk. Instead, they devour their prey while still alive. 

Data in this area is hard to quantify, but it could be speculated that predators eat live prey to reduce the risk of becoming sick. This is because the prey’s immune system is on constant alert, attacking any foreign pathogen invaders, keeping the animal alive and healthy.

Reason 4: Freshness 

A follow on from the above point, but still deserving of a heading of its own.

Deviating slightly away from the infestation of bacteria, keeping prey alive ensures optimal freshness and high nutritional value. 

Take the tarantula hawk wasp, for example. 

This is a parasitic species of wasp that lays a single egg on an unsuspecting tarantula victim. As the larva develops, it bores down into the internal cavity of the arachnid host to feast upon the wealth of nutrients available. 

Venom, injected by a mature female, paralyzes the intended host. The venom does not kill the tarantula, as the developing larvae need the host alive to derive nutrients. The venom also acts as an immunosuppressant, preventing the host’s immune system from attacking the developing larva.

However, and it is still not widely known just how, but these larvae actively avoid consuming vital organs. This, rather gruesomely, prolongs the suffering of the paralyzed spider, as the larvae continue to feed and grow on the available nutrients. 

A walk-in, living pantry, if you will. A safe, sheltered space, with on demand food supply.

Reason 5: Physical Characteristics 

The last reason we’re going to touch upon, is the physical characteristics of certain predator species. 

Wild cats, such as lions and tigers, are built to kill. They have large skulls, with sharp teeth, capable of delivering fatal bites. 

But what about predators that are smaller, lack certain weaponry or live in different environments to their prey? How are these animals able to hunt and consume their prey?

Well, a plethora of physical adaptations allow these predators to consume their prey alive, without having the need to kill it in the first place. 

Crocodiles and alligators, for example, hunt mostly in the water. While some are able to deliver a fatal bite (this is typically reliant on a prey species coming close to the water edge to take a sip of water), most crocodiles rely on a technique referred to as the death roll

Migrational mammals, such as vast herds of wildebeest found on Africa’s Serengeti, must pass stretches of rivers – the habitat of the prehistoric reptiles. As these animals pass through the water, the crocs clamp down on its prey using their powerful jaws, and perform a series of barrel rolls. 

Crocodiles cannot chew their food. Instead, the barrel roll technique rips limbs from bodies, allowing crocodiles to feast upon live animals in smaller chunks. However, more times than not, their prey species will die of shock or drowning. 

Other animals, such as predatory fish, do not have a means of killing their prey prior to consumption. Instead, most deploy an ambush tactic – laying in wait, before sticking at a lightning fast speed. 

This is especially apparent in fish species with protrusible jaws, such as bottom-dwelling, ambush hunters, like the stonefish. Laying in wait for smaller fish to swim by, the stonefish will suddenly extend its mouth, creating a vacuum, dragging its live prey to their demise. 

Slowed down to 1500 frames per minute, you can see just how fast a stonefish strikes, and the vacuum it creates:

Closing Thoughts

The animal kingdom is brutal. 

No matter what animal group you belong to, whether it is mammal, insect or fish, dangers lurk around every corner. 

Parasitic wasps want to devour you from the inside out. Crocodiles will tear you limb from limb. And fish will suck you in within a fraction of a second. 

All this, whilst you’re still alive. 

But this is the nature of, well, nature. Species have evolved to find shortcuts and tactics to help them survive and pass on their genes to the next generation. 

If any predator has to survive by ripping chunks of flesh out of its living prey, then that behavior has successfully been passed on through generations. 

We humans may not understand, or even agree, with the hunting behaviors of certain animals, but then again, the animal kingdom could argue the same about our current practices.