Will Chinchilla Siblings Mate?

It’s commonly advised not to keep sibling chinchillas of opposite sexes together. Is the problem that they will mate? And if they will, why, and what might go wrong?

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It’s commonly advised not to keep sibling chinchillas of opposite sexes together. Is the problem that they will mate? And if they will, why, and what might go wrong?

Will chinchilla siblings mate? They will if you keep them in the same cage. You should avoid this happening because inbreeding makes the expression of recessive genetic problems more likely. To prevent this, separate the chinchillas when they are almost fully weaned at 10 weeks or so. If you leave them any longer, they will begin fighting and mating.

The guide below first explores what happens if sibling chinchillas mate, and why they will, even though it can trigger genetic issues in the pair’s offspring. We’ll briefly look at what line breeding is (because some breeders do breed related chinchillas!) before moving on to how to stop sibling chinchillas from mating entirely.

Will Chinchilla Siblings Mate?

If you left an adult male chinchilla and an adult female chinchilla in the same cage, they would eventually mate. There is no way to avoid this, and as such, you should never keep male and female sibling chinchillas in the same cage. The only exception is if you are a knowledgeable breeder and are running a line breeding program, but if you don’t know what you’re doing, this can go wrong and you may have to cull large parts of your herd.

What Happens If Chinchilla Siblings Mate?

Baby chinchilla

First things first, chinchillas are fertile creatures. So if you keep siblings together, and they mate, it’s likely that the female will become pregnant. If not, they will continue mating until they do.

Contrary to popular belief, inbreeding does not cause genetic issues in every single offspring. It’s possible that the resulting kit or kits will be perfectly healthy. However, it’s much more likely than usual that they will have some kind of genetic abnormality, whether visible or not, that will cause stunted growth, difficulty performing certain tasks, failure to thrive and/or early passing. These issues become more common and more pronounced if you then breed these second generation chinchillas to one another, and so on.

The most common health issue influenced by genetics is malocclusion. This is where the chinchilla’s teeth grow too long, at an incorrect angle, and/or don’t meet properly in the middle. The sharp edges of its teeth can cut into your pet’s gums, and as the roots of the upper teeth grow, they can even damage the eye socket. Some chinchillas are more prone to this condition than others, seemingly because of genetics. Another issue you might encounter is infertility, which commonly affects animals breeding within the same genetic line, chinchillas or not. What breeding siblings won’t do is cause genetic issues to appear out of thin air. If the pair aren’t carriers of any genetic issues, then their offspring won’t be either.

All that being said, there isn’t typically an issue with the pregnant female. Provided the female is old enough to carry and birth the litter, it will survive and be healthy.

Why Would Chinchilla Siblings Mate?

In the wild, siblings in many species will breed. Rodents are a good example. Many rodent species like rats and mice, and similar animals like rabbits, will display this behavior. The reason is that rodents have to breed as often as possible to ensure survival of the species. To understand why, it’s useful to think from the rodent’s perspective.

Take an average population of rodents in a town. In any given year, much of the population will be killed by cats, dogs, people, and even other rodents. Many more will die of accidents like drowning in pipes or on the roads, while rodents have a short lifespan as it is. The same applies to rodents that live outside of towns and cities, like chinchillas. There are many animals that prey on chinchillas, so they have to keep the overall population as large as possible.

One can observe the necessity of this behavior in facts we already know about rodents:

  1. Rodents have short lifespans
  2. Rodents become sexually mature relatively early
  3. Rodents have large litter sizes, so that even if one or two don’t survive to adulthood (e.g. because of genetic issues resulting from inbreeding) the rest will

But as always, just because something is natural, that doesn’t mean it makes sense or is the ‘best’ option. If you plan on breeding chinchillas, using unrelated chinchillas is, of course, best.

Can You Breed Sibling Chinchillas?

Breeding sibling chinchillas isn’t ideal because it can cause genetic abnormalities. That’s because when two animals breed, their genes combine to form the offspring, which has 50% of its mother’s genes and 50% of its father’s genes.

Even two entirely unrelated chinchillas can have genetically abnormal offspring if they are both carriers of a certain ‘bad’ recessive gene. But if the pair are siblings, if one is a carrier, it’s highly likely that the other sibling is too. That’s why ‘inbreeding’ is a problem.

All chinchillas are closely genetically related anyway. That’s because all pet chinchillas are descended from only a dozen or so specimens that were trapped in the wild, and brought back to the U.S. to be used in fur farms. This makes inbreeding even more of an issue, because chinchillas don’t have a wide gene pool to select from as it is. So, if you’re planning on breeding chinchillas, we recommend against pairing siblings, at least as a regular part of your breeding program.

What Is Line Breeding?

Line breeding is where you breed together two animals in the same genetic line so that you can breed for a particular trait, such as thick fur or a stocky body. This doesn’t necessarily mean breeding a brother and a sister; it could mean breeding a father to a daughter (perhaps the most common form of line breeding), or breeding half siblings. Many, if not all successful breeding programs use some kind of line breeding.

But no breeder simply breeds the same chinchilla line to itself forever. If there are any—and there will be—they will eventually become apparent. As such, all breeders introduce new chinchillas to the line periodically. They do so very carefully, picking a chinchilla that has selected traits that will add successfully to the line.

How to Stop Chinchilla Siblings Mating

Whether you breed chinchillas on purpose or by accident, this is an issue that you must be aware of. You must take steps to prevent siblings from breeding, otherwise:

  • You may have more chinchillas than you can take care of
  • Some chinchillas may be born with genetic abnormalities and have lessened quality of life, be in pain, or have to be put to sleep
  • The quality of your breeding stock will be lowered

The rest of this guide will focus on preventing these issues from occurring.

1) Separate Sibling Chinchillas When They Wean

chinchilla whiskers
Give each of the siblings its own cage, or alternatively, put same sex pairs/groups together.

Chinchillas (and all other mammals) go through a process called weaning. This is where the offspring stops feeding on its mother’s milk, and starts eating whatever food it will eat when it’s an adult. Pet chinchillas progress from milk to hay. This doesn’t happen instantaneously, but over a number of weeks, beginning when the chinchilla is about eight weeks old.

You shouldn’t separate the offspring from their mother the moment they begin weaning. That’s because chinchillas continue to learn behaviors like dust bathing and playing from their parents even past this point. 10 weeks is a good point at which to separate them.

There are different ways to then house the offspring chinchillas. You can place them in same-sex pairs without issue. You could also house them alone. You can also place them in a same-sex communal cage if there are more than two, but be aware that this is more likely to cause fighting (the more chinchillas, the likelier this is).

2) Keep Track of Which Chinchilla Is Which

If you run a professional breeding operation, this is something that you’ll already do. But it’s vital that you keep track of which chinchilla is which to avoid accidentally pairing up chinchillas that are too closely related.

This issue could arise if you separate the chins into their own cages, but forget which is which. If you then picked out a breeding pair later on, you could pick a brother and sister out without meaning to. This is easily avoided by:

  1. Giving each chinchilla a name
  2. Keeping a chart (like a family tree) showing how each chinchilla is related to the others
  3. Labelling each cage to keep track of which chinchilla/s are inside it
  4. Taking photos of each chinchilla for reference
  5. Regularly bringing in good breeding stock from other breeders

None of these things will take too much time and effort, so are all worth doing.

3) Can You Keep a Brother and Sister Chinchilla Together?

Unfortunately, there is no way to stop sibling chinchillas from mating. If they live as cage mates, they will mate eventually, whether you like it or not. And the result of that will be that they have a litter together. The only way to prevent them from having offspring is either neutering the male or spaying the female. However, both of these invasive procedures aren’t recommended because they could, potentially, kill your pet. All small animals are sensitive to anesthetic; that’s because it’s easy to give a small animal the wrong amount.

As such, we recommend keeping same sex pairs instead. Failing that, you can keep each chinchilla on its own. We don’t recommend that novice owners keep opposite sex chinchillas together at all, but if you will anyway, at least pick two that aren’t of the same line.

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New owner, don't know where to start? Or do you need a handy chinchilla reference guide? Check out our Chinchilla Care 101 eBook, or get what you need from our online store!