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How to Breed Dogs of Different Sizes?

↯ Key takeaway points

  • Breeding dogs of different sizes can pose challenges and requires caution.
  • Puppies from dogs of different sizes are likely to be an average of their parents' size and may be limited by the size of a mother's uterus.
  • Smaller male dogs may need help mounting larger female dogs during mating.
  • Large male dogs may need to be assessed for compatibility with smaller female dogs before mating.
  • Pregnancies resulting from mating between dogs of different sizes should be closely monitored by a vet, and may require a C-section.
Breeding Business is passionate about all sorts of domesticated pets. They have written dozens of articles across the web.
Gold medalist veterinary student from UVAS Lahore writes captivating articles and is passionate about animal care.
Published on
Sunday 1 April 2018
Last updated on
Thursday 18 May 2023
How to Breed Dogs of Different Sizes
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Breeding dogs of different sizes may be challenging, or worrying even. Indeed, a smaller male may struggle to mount a bigger female; and a small female may be in utter pain with a much larger male. Although dogs are one and only one species, their huge disparity in appearance will raise some understandable questions.

First and foremost, when discussing how to breed two dogs of different sizes, it is important to know if the male is the smaller dog or not. If the male is much smaller than the female, you may require artificial insemination. On the contrary, if the female is much smaller, a c-section might be required as the puppies would potentially be too large for her birth canal. Read our article listing the top dog breeds going through c-sections.

Critical timings for a breeding of dogs of different sizes are the mating itself with the coitus and the delivery of the litter of puppies. However, do not underestimate the strain of the pregnancy that a smaller female would have to endure. Basically, puppies are an average of their parents for most traits, including size. The small female has a uterus designed to accommodate puppies from her breed and will, therefore, become uncomfortable with larger fetuses and whelps.

How to Breed a Smaller Male Dog With a Larger Female

In general, if a smaller male dog is determined to mate with a larger female dog, his sexual desire will be strong enough that he will find a way. However, this doesn’t mean there aren’t risks involved and your male dog may need a helping hand. It is best to let him begin proceedings alone but be sure to step in if you see things going awry. It is also best practice to take both sexual partners for a full health check before encouraging them to mate, as any existing health conditions may be exacerbated by the process or may not make them a suitable genetic partner.

The first step your male dog may struggle with is mounting the female. He needs enough height to get up on top of her to penetrate her. If he cannot get high enough, you will need to find a suitable sturdy platform to give him the boost that he needs. Ensure you place it on a non-skid surface and that it has non-skid feet so that your dog will feel sure of his footing. It is also worth introducing the mating partners before the onset of the female’s fertile period (9-14 days after she goes into heat), so they can get to know one another’s smell. This should reduce anxiety levels next time around, meaning that all the dogs’ energy can be focused only on the task ahead.


Once the male has reached a height where he can penetrate the female, he may need some help to stay there. It can take a couple of minutes for the bulbous glands in his penis to begin to swell in preparation for the lock. Whilst this is happening, you can place your hand under his tail and push him firmly up so that his chest lifts onto the female’s back and his feet come off the floor. Hold him here until the male and female are both safely locked.

The next step is possibly the most important as it is where the most damage can occur. The mating lock can take place from anywhere between 15 and 40 minutes. A male dog who is of a similar size to the female will usually lift his leg over the female and turn his back to her. The two dogs will then stand back to back for the duration of the copulatory lock process. However, for a small male dog, lifting his leg over a huge female dog and turning around will not be an easy task. You may need to lift his leg over very gently and help turn him around. This process can seriously injure both dogs if not done correctly.

Once your dog has turned around he will still need some help to stay leveled with the female’s vagina until the lock is complete and he is released. You can place your dog back on his sturdy platform but ensure it is high enough to keep him reasonably leveled with the female as an extreme pulling on his penis may cause damage.

Throughout this process, you may also need to hold the female still so that she isn’t dragging the smaller male around by his penis. Depending on the height discrepancy, sometimes it is enough to just hold the female still throughout the whole process while the male gets to work. You may also be able to encourage the female to lie down on a cushion, so the male can get to her more easily. Never try to force the two dogs apart; always let lock finish naturally. In extreme circumstances, the process can take a full hour so be patient and never leave the dogs unsupervised.

How to Breed a Smaller Female Dog to a Larger Male

the size of a puppy is determined by the mother
The size of a mother dog generally determines the size of her puppies.

There are far more factors to consider when breeding a small female dog to a large male, than when breeding a small male to a large female. There are situations where it may seem apparent – even without any specialist knowledge – that the size discrepancy is too extreme and could even cause lethal bleeding. In this instance, the two dogs should never be encouraged to mate. However, there are various situations where with a little help a female can successfully produce a bigger litter of puppies.

Firstly, assess whether the weight of the male dog can be tolerated by the female without causing injury as many small dogs (especially Dachshunds) have very delicate spines. Generally, the female will not be burdened with the entire weight of the male dog, but if he is exceptionally large there is still a risk of damage. There is also a lot of wooing involved before mating occurs – this often includes biting and pawing each other, which could cause unintentional harm. If you may need to separate the dogs at this stage if the male is too rough.

It is also possible that some male dogs will have a penis that is far too large to enter the female. Attempts to penetrate the female could rip her vaginal opening. If you are unsure whether the two mates have compatible genitalia it is best to seek advice from a vet before subjecting your female dog to potential mutilation.

If your male dog can successfully penetrate the female and enter the lock, you must keep them very still. There have been cases, where male dogs have been known to run around while still in the tie, dragging a yelping female dog around the garden. This is extremely distressing and could even be fatal for the female. Always closely supervise the dogs and as with any dogs in the lock, never attempt to separate them – wait, and let nature take its course.

[pullquote-left]The more puppies a mother is carrying, the better the outcome.[/pullquote-left]

It is unlikely that the male will be able to turn away from the female during lock if she is exceptionally small. Chances are he will have to stay poised over her until the process is complete. During this time, make sure he doesn’t lie down and squash her – keep checking for any signs of distress from either party.

If the large male dog successfully impregnates the small female, there is a strong possibility that she may need a C-section to deliver her puppies. It is exceedingly common for small dogs to have fetuses that are too large for the birth canal, complicating the natural birthing process. The mother may die pushing out puppies that are far too big for her body.

Generally, the more puppies a mother is carrying, the better the outcome because they will all have to stay within the limits of what the uterus can carry. And, of course, they all must share the space, so they can only grow so big. The problem comes when the mother is only carrying one or two puppies as they will have more room to grow until eventually, they will no longer be able to pass through the birth canal.

If your small female dog is carrying a larger dog’s puppies, she must be monitored extremely closely by a vet from conception to birth. You do not want her to go into spontaneous labor with puppies she cannot feasibly deliver by herself as neither the mother and/or the pup(s) may survive.

Frequently Asked Questions

By now, you probably understand the essence of the problems at hand. Breeding dogs of different sizes is totally possible but will most likely call for some discomfort and human help. Precisely, artificial inseminations instead of natural matings, and cesarean sections instead of natural births.

Yet, you are somewhat unsure about this whole situation and still have some questions. We’ve compiled these most frequently asked list of questions and answered them as precisely as we possibly could.

Can very large breeds mate with toy breeds without assistance?

Strong-willed dogs who hear the call of nature will generally always try to find a way to breed and mate, so it’s possible that it can be done without assistance. However, toy breeds are not physiologically designed to mate with larger breeds, so the process can be clumsy, risky and potentially dangerous. As a firm general rule, you should never leave any dogs to breed without assistance – especially dogs with extreme differences in height– as they can run into problems, especially during the tie process.

[pullquote-right]No matter how large the father is, the mother’s uterus is only so big and will restrict the size that the puppies are able to grow to.[/pullquote-right]

It is particularly important not to leave large males and small females alone during coitus as it could cause extensive damage or fatality for the female. She could easily be dragged around by a strong male whilst in lock. She also risks being crushed by his weight or splitting her vaginal opening if the penis is too large. A small female dog who has mated with a large male dog should never have an unmonitored pregnancy as the risk of having puppies that are too big for her to deliver is high.

All breeding between big and small dogs should be closely supervised under the advice of an expert. Both the male and female should also undergo a full medical examination before coitus to ensure that they are fit for the act as it can be a lot more taxing than coitus between two dogs of the same size.

What will be the size of the puppies born from parents of very different sizes?

Puppies will generally get most of their size from their mother because their in utero growth is constrained by the size of the mother’s uterus. No matter how large the father is, the mother’s uterus is only so big and will restrict the size that the puppies are able to grow to. The number of puppies a female is carrying will also affect their size. If she is only carrying one puppy, chances are it will be a lot bigger as it has a lot more space to grow. Whereas, if she is carrying four puppies they can each only occupy a quarter of the uterus and will be competing for space which will limit their eventual body size.

If the puppies have a small father and a large mother, they are still likely to be on the larger size as the mother has a larger uterus allowing them more room to grow. However, their father’s genes will still place limitations of their size and the puppies will be unlikely to be as large as their mother when they reach adult size.

Is it safe to breed dogs of different sizes?

It can be safe to breed dogs of different sizes with the right supervision and attention from the owners. You should also seek help and advice from a vet who will first be able to tell you whether the difference in size between two dogs is too extreme. There will be risks from coitus, right through to delivery. Especially when breeding small females with larger males due to the obvious risks presented at the time of the penetration. Thus, you should ensure that you are aware of the risks and of what to do in an emergency, before beginning the breeding process.


The risks range from minor genital injuries during lock to potential death of the female and her pup(s) during labor. Even with careful supervision, mistakes can happen so think very carefully about the risks you are prepared to take to breed a large and small dog. Just because a dog’s natural instincts are leading them to want to mate with someone much bigger or smaller, it doesn’t mean this is the right thing to do. Make sensible decisions on behalf of your dog!

How do small males mount bigger females?

A small dog who is determined to mate with a larger female dog will generally use all his strength and might to try and achieve penetration. However, he may struggle, and he may never get there because he’s simply not tall enough. Some small dogs will leap up onto the back of the female, hold on tight and hump until they get it right. They may also stay up there during lock. Nevertheless, there are times where the dog may not be strong enough to hold on (maybe the female also won’t allow him to hold on) or is doing all the right movements but is still falling short.

Many dog owners give their dog a gentle helping hand. You may need to provide a sturdy, non-slip platform for your dog to stand on and help him reach. You may also have to firmly but gently place your hand under his tail and give him a boost up onto the female and help him stay there while the pair enters the lock.

Due to the length of the lock process (15-40 minutes on average), the male usually lifts his leg over the female and turns his back to her until he is released. It is likely that very tiny dogs will not be able to achieve this alone – you may have to lift your dog’s leg for him and turn him around. Even then, if he is very small he will not be able to stand rear to rear with the female because of the difference in height. He will need to have all four legs back on his sturdy non-slip platform which should make up the difference in height.

28 comments on “How to Breed Dogs of Different Sizes?”

  1. Drooder

    This was very helpful in breeding my 7-pound male chihuahua with my 120-pound female mastiff. I think she may be pregnant! Thank you!

    1. Susan Edgerton

      Picturing the the process of large dog and small dog breaks my heart for the small dog. The inhumanity of man

      1. Logan

        It is definitely heartbreaking what some people do. So many people lack empathy.

      2. Deeps

        I found this website as I was looking for a mate for my female chihuahua who is fixed.

        I cannot imagine so many people want to play mix and match with different breeds. Please check the local shelter. There is no shortage of puppies in this world. Stop playing god.


      hi, This is a very interesting pairing. I would love to hear how it turned out and possibly see photos if your female mastiff did become a mother. We have a female Saint bernard and toy breed, Brussels Griffon. Thank you so much for any help!

      1. Mariela Romero

        Would it be safe to breed an 8lbs maltese female with a 12 lbs mini poodle male?

        1. Mary Maloy

          That’s exactly my question. Did you find an answer?

        2. len

          Ihave a 19 lb dog can he breed with a 12lb female

  2. Lori

    Hello I have a 9 lb Shihpoo and a 15 lb shitzu. Is it safe for them to breed.
    I look forward to here from you.
    Thank You
    Lori Skidmore

  3. William

    Please don’t mate dogs of different breeds, this can bring complications. If you’re going to mate dogs, do it with same breed.

    1. Its_Zeesh

      Are you a vet or specialized in animal health? No. I don’t think so. I got a very mixed dog at home from the shelter and she is smart and there is nothing wrong with her. How do you think we even got dogs. Breeding of different wolves. It’s normal, don’t tell people what to do with their animals as long as they aren’t hurting them.

  4. Angela

    Hi there, I have a male Pomeranian around 8.37lb, will that be safe to breed with a female Maltese which is around 6lb? Cause we’re planning to breed Maltipom puppies.
    Looking forward to hearing from you soon.

    Many thanks!!

    1. Lisa

      I have a 7.6 pound male Maltese can I breed him with my 4 pound female Morkie? Thank you Lisa

  5. Ashley

    Hi I have a 10lb Female Shihtzu and she bred with my 16lb Mini Poodle. She should be fine right. I know a few people who bred their smaller Female Shihtzu to their bigger Mini Poodle before.Their difference in size was 5lbs and my difference in sizes are 6lbs.

    1. Tammy Staley

      How did the birthing work out, I will have a similar experience ?

  6. Joanne Perry

    True. Its all depends on male dog size because they are in small and big sizes, will succumb to their natural instincts and try to mate with female dogs regardless of their size. But according to my opinion, if female dog is in a large size or comes from toy breed then she suffering a lot of pain.

  7. Julie Bertacini

    I have18 lb mini goldendoodle female. What is the largest male goldendoodle I can breed her with safely.

    1. Terry

      Hi I have a 10lb Female Shihtzu and she bred with my 16lb Mini Poodle. She should be fine right. I know a few people who bred their smaller Female Shihtzu to their bigger Mini Poodle before.Their difference in size was 5lbs and my difference in sizes are 6lbs.

      1. Bertie Sirrine

        Why do you have females in heat being allowed to mingle with your other dogs at will. You’re not very responsible with their well being. I hope you take good care of the puppies.

  8. Sue Duran

    I have a question I have a 50# female dog tried to breed to 99# dog unsuccessful what can we do next time different female dog it is her first litter

  9. I won’t breed until I’m 100% sure but could a 7lb yorkshire terrier have pups to a 9lb tibetan spaniel both or same height just body weight is different.. head sizes also which worries me. I’ve been looking for this information for past few weeks so your advice would be most appreciated

  10. Brooke

    Omgosh my 94 lb male may have impregnated by 20 lb female! That’s way too much of a size difference isn’t it?

    1. Trish

      My goldendoodle is 60 lbs.
      Can she be breed with a Saint Bernard or is it safe? Both her parents are goldendoodles.
      She will be 2 yrs old this Dec/2021 & this would be her first & only litter, then spayed. Thxs

      1. A M

        Just why tho? There is literally no benefit to your dog having a litter before it gets spayed.

    2. A M

      More than the size difference Id be much more concerned that your male dog is impregnated😳! 🤦‍♀️

  11. Cheryl Gomes

    Can my golden doodle stud @30 lbs sire a litter with a petite golden doodle @16 lbs???

  12. Billie oneal

    My dog is a rat terrier Chihuahua mix and our mail is Pomeranian and terrior mix is safe to let them breed

  13. Eileen Kay Buck

    I have a petite female husky they get impregnated by a pitbull bully. Will she be OK to deliver these puppies or with the puppies be too big and should I take her to the vet?

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