Interesting Facts About the Runt of the Litter

Interesting Facts About the Runt of the Litter

Runt of the litter dogs are often quite misunderstood, and the term itself is also often misplaced. There are a lot of questions around what constitutes as a runt, and there are also as much myths as there are questions!

If you’re a dog parent to a mama dog that just gave birth or are planning to get your own puppy and were told it’s a runt, this blog post will help you understand what a runt actually is, answer questions you might have, bust some myths, and advise you on how to take care of one.

Let’s break it down!

What is the runt of the litter?

A runt is not a scientific term but is commonly used to describe the smallest or weakest of the litter.

Although there is no universal consensus on what a “runt” is, it usually refers to a puppy whose weight is abnormally low – lower than the healthy level for that specific breed.

By that definition, there can be more than one runt!

Why makes a runt?

Poor Implantation

According to Dr. Margaret V. Root Kustritz, a board-certified veterinarian theriogenologist (the branch of animal science concerned with reproduction), runt dogs are a product of poor placentation or a comparatively poor implantation site in the uterus.

Her book, "The Dog Breeder’s Guide to Successful Breeding and Health Management", explains that a certain placenta malfunction could stand in the way of an adequate supply of oxygen and nutrients getting to the runt from its mother’s bloodstream.

This obviously hinders the runt’s growth and, consequently, its changes of thriving.

Survival of the Fittest

Natural selection could be another way to explain this process. Runts are commonly seen as having physical disadvantages that prevent them from getting adequate nutrition.

With as much competition among the litter for access to milk and warm spots near the dam, puppies that would’ve already had these physical advantages early on tend to be stronger and grow faster.

This means runts, or whoever was born smaller, would be the last ones to eat; resulting in even more inadequate nutrition and growth.

Interesting Facts About the Runt of The Litter

  • Interestingly enough, a runt is not necessarily determined at the time of conception!

  • They could be, but in some cases, what was not born a runt could become a runt.

  • We’ve talked a bit above about natural selection. If a puppy does not look evidently smaller at the time of birth, the difference in size will start to show over time because of the disadvantaged feeding.

  • Runts sadly have their odds stacked against them – they are often also ignored by their mothers. Once a mama dog notices an ailment in her litter, she tends to focus on the healthier pups.

  • This is also a product of natural selection! But unfortunately, that rejection can hasten the runt’s death.

Health Implications

The runt of the litter is unfortunately more prone to medical risks, the worst of which is death. Their abnormally low birthweight calls for a higher mortality rate, and they’re also associated with these health issues:

Colostrum Milk Deficiency

After 24 to 48 hours after birth, the dam produces a special milk called Colostrum with magical immune-developing properties. Because runts can’t latch on to suckle because they’re weak, there’s a risk of failure to drink the milk. This hinders the development of his immunity and vitality, possibly causing illness and infections.

Fading Puppy Syndrome

Fader puppies become lethargic, vomit, have a frequent high-pitched cry, and are unable to gain weight during the first two weeks after birth. This slow deterioration of their health could lead to rejection and can be fatal.

Congenital Problems

Inadequate access to nutrients in the uterus can hinder development and lead to genetic defects in the runt.

Prone to Parasites and Infection

Puppy bodies, especially those of runts, make better hosts for parasites like hookworms because they are less able to withstand the load.

But even with all these susceptibilities, runts can still thrive with the proper human-intervention, love, and care!

How to Care for a Runt of the Litter?


Not all runts die – if you provide them with the proper care that substitutes what they couldn’t amount to before and during birth, a runt can still grow to be a healthy puppy!

It’s important to make sure a runt of the litter dog gets enough milk to prevent dehydration and hypoglycemia, which includes Colostrum. They might also need to be handfed.

And since the puppies are sometimes unable to secure themselves warmth due to dam competition, you can keep them warm from birth yourself by moving them closer to a privileged spot near the mom or maintain a warm room temperature if indoors. You can also use a heat pad or lamp!

As usual, always consult your vet and work with them towards creating a plan. Professional advise will only further ensure your puppy will better grow into the healthy dog he should be!