Canis lupus familiaris gestation and postnatal development

Puppies are cute. We don’t often get to see them in utero, but now we can, thanks to this sweet radiograph courtesy of my mom, a Labradoodle breeder at Red Rock Doodles. Can you guess the number of puppies by counting the heads and tails? How many do you see?

I think puppies are fabulous, but our Content Editor, Chris Givens, told me I couldn’t just post pictures of puppies and other baby animals on The Pipettepen. He said we were better than that and that our posts must have scientific merit and meaning. So here it is:

5 Scientific facts about puppies and other baby animals:

1. Canine gestation lasts for ~63 days. For comparison, humans have an average gestation period of 280 days, and elephants have a whopping average of 660 days. Yet, all three yield cute baby animals (see Tumblr et al.).
2. It is common for puppies to be born ‘breech’, or tail-end first. In dogs and other animals where this occurs frequently, this presentation is referred to as ‘posterior.’ Dogs are unusual even among other polytocous animals (animals that typically produce more than one offspring at a time), in that there is no statistical difference between incidences of posterior and anterior presentation. On the other hand, pigs can birth up to 20 piglets in one farrowing, but have significantly more anterior presentation than posterior presentation births, with incidence rates of 62% to 38% respectively. Humans have a measly 3% posterior presentation birth rate. The research on this topic does not provide a consensus as to why or how fetuses know to turn, or why dog fetuses have no need to turn in utero.
3. Each puppy has its own placenta and umbilical cord, and therefore a bellybutton. This is true of all mammals, except marsupials and monotremes. Next time you are rubbing a puppy belly, check whether it has an innie or an outie!
4. At birth, puppies can respond only to touch and taste; their other senses develop over the next 9 weeks. Puppies do not open their eyes until 10 days after birth, and their ears stay sealed until around 15 days. During this time, their sense of smell continues to develop and mature.
5. Dogs, cats, and humans are examples of altricial organisms, which need substantial nourishment from a parent following birth. Horses, cows, hipppos, deer, guinea pigs, and some species of hares are precocial, meaning they do not need as much post-birth support. This is particularly interesting as rabbits are highly altricial, suggesting that this trait is not highly evolutionarily conserved.

Note: Radiographs are somewhat dangerous during early gestation, which is why most women receive ultrasounds during the early months of pregnancy. Ultrasounds are safe at all stages of pregnancy, though cost significantly more. Performing radiographs on pregnant dogs a couple of days before birth gives breeders an idea of how many puppies to expect, and allows vets to look for warning signs of complications to come.

Peer edited and reviewed by Deirdre Sackett & Jonathan Susser

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This article was co-published on the TIBBS Bioscience Blog.