Do Spiders Eat Their Babies? (Solved!)


As gruesome as this sounds, a lot of animals will and do eat their babies. The common layman’s term for this is animal cannibalism. This group of baby eaters can include bears, domestic cats, reptiles and birds to name a few. But are spiders one of these animals?

Although spiders do occasionally eat their babies, this is quite rare. It is more likely that the babies will sometimes eat the mother, an act known as matrigraphy. Very occasionally a mother may eat her babies, but this is usually when she is not fully equipped to rear them (for a variety of reasons).

So, while they do eat their babies, things are not as easy to understand with spiders as it is for other animals.

So, let’s look into why a spider could eat their babies, and also the times when that is most likely to happen. Be warned, this is going to be different to what you would expect to happen.

Baby spider on a finger

The Biggest Sacrifice A Mother Can Make

A mother spider rarely eats her young, although from time to time she will. Not all spiders are alike, and the most interesting caveat to take away with this idea is that the spiders’ babies are more likely to eat their mother than she is likely to eat them. Now, that is a surprise that most people would not expect to happen.

The act of allowing your offspring to eat you is known as matriphagy. It too is a rare event, but a spider is one of those creatures that can, from time to time, let this happen. It really is the biggest sacrifice a mother can make for the sake of the future survival of their young.

But spiders that allow their offspring to eat them normally produce fitter baby spiders than those who do not. That means a better body weight, are more defined, and have an acute ability to survive, as well as having faster molting times.

Basically, it helps those baby spiders to grow up stronger than they would have otherwise been, and it’s all thanks to their mother sacrificing herself for them. It is the biggest way in which a mother could give her young the best chance of survival.

Spider Cannibalism And Reasons Why This May Occur In The Species

As another quick note, spider cannibalism is more common when it involves two adult spiders. This issue of a spider eating their babies is certainly more on the rare side of things.

So, let’s quickly address the issue of spider cannibalism in general. The fact so many people know spiders can eat one another is part of the reason why there is a type of fascination over the idea that a spider will also eat its babies. After all, if they can eat one another, why wouldn’t they also be interested in eating their offspring?

Like all species, spiders can evolve and change, and not that long ago it was believed that all or most female spiders would eat their mate after mating. This is not as common as one would anticipate and exists in certain species only. So, that does instantly pour some scorn on what we previously thought about spiders.

Some widow spiders, for example, seem to allow itself to be eaten gracefully after copulation, and he does this by flinging himself under the fangs of a female spider once they have mated. This is the reason they are called widow spiders. However, even widow spiders are evolving and have slightly changed their mating habits so that they can survive the process. [Source]

Often, instead of mating with fully grown females, the redback widow has found a way to avoid being eaten, before, during or after the mating process.

A male spider will choose to copulate with an underdeveloped female spider. This was not considered possible before, since underdeveloped female spider genital organs, although developed, were closed away and sealed. The male found a way to slice away at the sealed opening and copulate without having to be eaten afterwards. 

Most of the time, male spiders can copulate with female spiders and leave completely intact. There have also been occasions where the male spider has devoured his female counterpart instead of the other way around. Though this is admittedly very rare.

Babies spiders

The Reason Why Parents Eat Their Babies Is Varied

With other animals and insects, including arachnids, this can occur for a variety of reasons, and scientists have discovered new theories as to explain why. One thing is for sure, and that is that no two reasons are the same. Often an animal will eat their young simply because the young cub or baby was not well enough to survive. 

Some babies rescued from mothers were found to be very unwell shortly after the rescue. This is probably natures way of taking care of animals that could never have survived in the wild anyway. A spider is not going to be immune to those types of pressures or trying to deal with that type of situation.

Another reason could be that the mother was not strong enough to feed their other babies without the sustenance of food, and food could have been in short supply. So one baby can be eaten while the others are left alone. Food can be a great determinant of whether that particular animal will eat their offspring, after all animals know they have to eat in order to survive. 

But remember earlier on when we mentioned a mother allowing their babies to eat her?

There are particular spiders that survive on very little energy and movement, and the mere act of giving birth is exhausting for them. As a result, they will then allow their offspring to eat them. They simply see mating and giving birth as the final part of their life.

Is It An Act Of Bad Parenting?

This can happen with female spiders. She might not be in a good energy position to care for her baby spiders. So instead, she will eat them and then mate again to be a better mother to her new baby spiders.

This does sound bizarre to us, but logic is different in the animal world. It’s almost as if they seek to learn from one event to then be better in the future. So, is it bad parenting? Well, eating your young is not good, but it ties in with what we just said regarding the way in which they may not have survived in the wild for long. In that case, is it an act of mercy rather than bad parenting?

The Unselfish Act Of Matiphagy

So, this act of matiphagy, otherwise known as a mother allowing her young to eat her.

The bigger factor in animal cannibalism is the utterly unselfish act many mother spiders will do to care for their baby spiders. She will allow them to devour her instead as a good source of food. [Source]

These little spiders will grow up and later do the same sacrificial move for their little hungry babies too. This is the more common scenario. Even aunt spiders have allowed their siblings’ babies to eat them as well. 

Often baby spiders will eat each other, and if they are feeding off their mother, literally this can prevent this phenomenon. 

All in all, the reasons why spiders can eat other quite frequently is the very basic instinct for survival. Food is food, and if food is scarce, anyone can become their next meal if they are vulnerable enough.

Most spiders operate in a similar way, but many have distinct traits that will either encourage cannibalism or not. Nature has a wonderful way of procuring the next generation, and a mother spider offering herself up for dinner certainly is a good step to ensure providing that type of survival. 

Summing It All Up

So, to sum everything up, a spider can indeed eat their babies, but the babies can also eat them.

That’s why spiders are different to so many other creatures that indulge in animal cannibalism. It can work in any direction and is not a one-way street. Of course, some spider species can then eat one another at any stage in their lives, so don’t think for a second that it’s a case of a spider being safe once it gets past the baby stage. That is not always the case, but keep in mind this is just nature working, even if the idea seems alien to us.

Barry Gray

Barry is a freelance writer from Scotland. He has written about pets for over a decade, and his work has been turned into a range of ebooks, courses, and material for diplomas. Barry is passionate about all animals, but particularly dogs, fish, rabbits, birds and spiders. You can find out more about Barry at https://mercurypets.com/our-writers/

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