- Not a substitute for professional veterinary help.
Choosing a puppy is a big decision—and sometimes a confusing one. A lot of pet parents wonder how to identify the best fit for their family among the squirmy little fuzzballs, especially when it comes to the runt. The runt is typically the smallest puppy in the litter, sometimes facing unique challenges because of their size.
With the help of expert vet Dr. Antje Joslin of Dogtopia, we’ll explain how runts work, the pros and cons of adopting one, and what you can expect as they grow. The bottom line: Despite some concerns, runts can grow into healthy, happy dogs with the right care.
What Is a Runt?
A runt is usually the smallest and weakest puppy in a litter. Scientifically, runts are puppies with low birth weights compared to their siblings. Studies show that being the smallest can sometimes mean extra challenges, like a higher risk of health issues during the first week of life.
In everyday language, “runt” is often used to describe the tiniest pup in a litter, even if its health is otherwise robust. While the term might sound worrisome, it’s not always a cause for concern. For example, if a large breed mixes with a small breed, there will likely be significant and completely normal size variations in the puppies.
According to Dr. Joslin, runts are often produced when a puppy has limited access to nutrition in the womb. Other times, the puppy is smaller because the embryo was fertilized on a different day.
Not every litter has a runt, and the size of the litter doesn’t determine whether there will be a runt.
TatyanaGl via iStock
Should You Pick the Runt of the Litter?
Welcoming a new dog into your home, regardless of their size, is an exciting experience and a commitment to give your new furry friend a full and joyful life. To make the most responsible and informed decision, it’s important to consider the potential pros and cons of choosing the runt of the litter.
When to choose the runt of the litter
In most cases, a runt can make a wonderful pet, as long as they show signs of good health. Here’s what to look for.
- They’ve received proper care early on. If the breeder or rescue has made sure the runt was supported with supplemental bottle feeding or other interventions, they’re more likely to catch up to their siblings in size and health.
- They’re active and social. A runt that interacts well with their siblings and shows curiosity about their surroundings is likely on the right developmental path.
- The breeder provides the results of the puppy’s health screenings and the screenings of the parents and grandparents. If the breeder is reputable, they should be willing to share the health history of the puppy and its parents, says Dr. Joslin. This will give you an idea of the puppy’s health issues (if any) and the potential long-term impact.
Signs that might make you worry
While runts can thrive, certain warning signs may indicate ongoing or future health issues. Dr. Joslin recommends being cautious if you notice the following.
- Poor growth and coat condition. If the runt is growing significantly slower than their siblings and has a thin or patchy coat, it could indicate underlying health problems.
- Gastrointestinal issues. Symptoms such as a low appetite, frequent vomiting, or diarrhea may point to long-term digestive challenges.
- Physical abnormalities. Some runts are born with an abnormal oral bite or cleft palate, which means they might continue to have health issues long-term.
Before making your decision, it’s a good idea to consult with a veterinarian to evaluate the puppy’s overall health.
Health Prospects of Runts
Research suggests runts sometimes face a higher chance of health challenges early on. For example, they might struggle to nurse as easily as their bigger siblings. In extreme cases, research shows 39% of puppies with very low birth weights may not survive past the first week. Other common health hurdles with the runt of the litter include:
- Low blood sugar (hypoglycemia)
- Trouble staying warm (hypothermia)
- Being more vulnerable to infections
- Congenital conditions like a cleft palate or a heart defect
In some cases, newborn runts need a little extra care from their humans to get on track with their health. For example, if they’re struggling to latch onto their mother or aren’t nursing enough, supplemental feeding with puppy formula can help. And to help regulate their body temperature, a heat lamp can provide extra warmth.
Once a runt gets through those critical early weeks, they often catch up and live perfectly normal lives. “For most litters, if the puppy is healthy, without a congenital defect, and can nurse appropriately, they can be healthy and catch up in size with their littermates,” confirms Dr. Joslin.
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Behavior Differences in the Runt of the Litter
There’s a common belief that runts of the litter often grow up with unique, endearing personality traits, like being more sociable or mild-mannered. This is sometimes attributed to the extra handling they receive from humans early on.
Research, however, isn’t so clear-cut. Studies tend suggest a puppy’s interaction with their mother matters more than their interactions with people in personality development.
For example, a study on Beagle puppies found that puppies who received more attention from their mother tended to handle stress better and explore with more confidence. Puppies who received less attention showed higher stress levels, like increased whining or yelping when left alone.
These behavioral patterns weren’t strongly linked to interactions with people, which makes it unlikely that a runt’s extra handling from humans really shapes their personality. But if being smaller led to different interactions with their mother, that might change some of their behaviors in puppyhood.
The key takeaway? Being the runt probably doesn’t predetermine a dog’s behavior. Runts can grow up to be wonderfully well-adjusted dogs, especially with love and training.
Prospects for Growth in Runts
One of the most common questions about runts is whether they’ll stay smaller than their siblings into adulthood. The answer depends on a mix of genetics and overall health. For example, if the runt has a birth defect, Dr. Joslin says they might remain smaller than their littermates for their entire life. On the other hand, a runt that receives adequate puppy nutrition and veterinary care can reach the same adult size as its littermates.
Wondering if your dog was the runt of their litter? It’s not always obvious. If they’re a purebred dog, it might be easier to tell if they were the runt because there are breed standards with specific weight and height requirements. So, if they are significantly smaller than the breed standard, they might be the runt of their litter. For a mixed breed, it’s a lot harder—if not impossible—to tell.
