Mother dog reject their new puppies for many different reasons. First-time moms may not understand what they are expected to do; moms overwhelmed by a large number of puppies may become too stressed to care for them. Although many people believe mother dogs will always reject the runts of their litters, this is not always the case.
Problems Facing Runts
Typically, runts are the babies who were positioned in the middle of the mother’s uterus, where they received less access to nutrition. Low birth weight can be a risk factor for health problems, including fading puppy syndrome, which often results in death. Runts who survive their first 6 to 8 weeks are likely to make it to adulthood.
Mothers & Runts
Contrary to popular belief, mothers usually do not reject the runt of the litter. In fact, mother dogs often try to protect them from their competitive siblings. Because they're smaller, runts tend to have a harder time competing with siblings for warmth and food. When mothers do reject the runt, it's not because he's simply too small. Mothers know when a puppy is too weak to survive, and they'll refrain from giving their resources to the pup. Except for those born with congenital malformation, most abandoned runts can be saved by hand-rearing away from the litter.
References
Writer Bio
Amy Jorgensen has ghostwritten more than 100 articles and books on raising and training animals. She is also an amateur dog trainer. She has also written more than 200 blog posts, articles, and ebooks on wedding and party planning on behalf of professionals in the field.