By Carol Beuchat PhD
If light inhibits the hormone that increases the strength of uterine contractions during labor, you want to whelp in a dark room to prevent uterine inertia and reduce the risk of stillborn or distressed puppies.
But how dark is dark enough?
You can't trust your eyes to tell this. First of all, you know that our eyes can slowly adapt to darkness, so you can't trust your eyes to assess light levels.
It's the light that interacts with the receptors in the dam's eyes that matters. Photons that reach her receptors for light intensity (not rods or cones) signal to her brain whether it is light or dark where she is, and this information controls the secretion of the hormone melatonin. It's photons interacting with the receptors in the eye that matter here, not what she (or you) can see.
Melatonin interacts with oxytocin during labor to produce the strong contractions necessary to expel the puppies during labor. Light blocks melatonin secretion by the pineal in the brain. So if the room isn't dark enough, the hormone that is critical for expelling the puppies during labor is inadequate, and the result is uterine inertia.
But how dark is dark enough?
You can't trust your eyes to tell this. First of all, you know that our eyes can slowly adapt to darkness, so you can't trust your eyes to assess light levels.
It's the light that interacts with the receptors in the dam's eyes that matters. Photons that reach her receptors for light intensity (not rods or cones) signal to her brain whether it is light or dark where she is, and this information controls the secretion of the hormone melatonin. It's photons interacting with the receptors in the eye that matter here, not what she (or you) can see.
Melatonin interacts with oxytocin during labor to produce the strong contractions necessary to expel the puppies during labor. Light blocks melatonin secretion by the pineal in the brain. So if the room isn't dark enough, the hormone that is critical for expelling the puppies during labor is inadequate, and the result is uterine inertia.
| We need to know the relationship between the number of photons reaching her light receptors and the secretion of melatonin. In bright light, melatonin secretion by the pineal is blocked. How low does the light level need to be to eliminate suppression of melatonin? How dark is dark enough? A "dim" room is roughly 20-50 lux. At night with a full moon, the light level is about 0.1 lux. Starlight at night is about 0.001 lux. We know that the light sensors in the eyes of diurnal mammals are extremely sensitive. Studies of the effects of dim light at night use light levels of 2-5 lux. Starlight blocks melatonin secretion in diurnal mammals. The difference in light levels of what we perceive at a dimly lit room is 4 orders of magnitude - a factor of 1,000x - more light than necessary to block melatonin secretion. To prevent suppression of melatonin secretion, it must be very, VERY dark. Your own eyes are worthless as light sensors at this level of darkness. |  |
For a bitch on a dark night in an underground den, the light levels must be lower than this or she will not secrete the melatonin necessary for contractions strong enough to expel her puppies.
When we whelp puppies in darkness, we must get the light levels in the room below the level that would suppress melatonin secretion. We don't know that that level is, and we wouldn't be able to measure it without an expensive sensor. So we simply eliminate ALL light in the room.
When we do that, everything about whelping changes. The behavior of the bitch is different, we stop seeing abdominal contractions (because the uterus is pushing the puppies out), the interval between puppies gets very short, and we stop seeing stillborn and distressed puppies.
We live in a world of light. Getting a room this dark is a real trick, and we have found that even the tinest amout of light, even very briefly, shuts down normal uterine contractions, usually for about 2 hours. This can be too long for a puppy already in the birth canal to survive on the oxygenated blood in the placenta and its circulatory system. We have found that this shut-down is very unforgiving. Any light shuts things down for hours.
The trick is to get the room dark enough for whelping, and to prevent ANY light in the room until all of the pups have been born.
When I supervise a whelping, my goal is to use my experience to help breeders get it right in the environment where they whelp their dogs. My other job is to reassure the breeder that we can see quite well what is happing from the video feed, and as long as things are going well, we are simply spectators. Of course, if there is a serious issue the breeder can just enter the room. The goal is 100% survival of normal puppies. In about two dozen dark whelpings, we have had no normal puppies that were stillborn or distressed.
When we whelp puppies in darkness, we must get the light levels in the room below the level that would suppress melatonin secretion. We don't know that that level is, and we wouldn't be able to measure it without an expensive sensor. So we simply eliminate ALL light in the room.
When we do that, everything about whelping changes. The behavior of the bitch is different, we stop seeing abdominal contractions (because the uterus is pushing the puppies out), the interval between puppies gets very short, and we stop seeing stillborn and distressed puppies.
We live in a world of light. Getting a room this dark is a real trick, and we have found that even the tinest amout of light, even very briefly, shuts down normal uterine contractions, usually for about 2 hours. This can be too long for a puppy already in the birth canal to survive on the oxygenated blood in the placenta and its circulatory system. We have found that this shut-down is very unforgiving. Any light shuts things down for hours.
The trick is to get the room dark enough for whelping, and to prevent ANY light in the room until all of the pups have been born.
When I supervise a whelping, my goal is to use my experience to help breeders get it right in the environment where they whelp their dogs. My other job is to reassure the breeder that we can see quite well what is happing from the video feed, and as long as things are going well, we are simply spectators. Of course, if there is a serious issue the breeder can just enter the room. The goal is 100% survival of normal puppies. In about two dozen dark whelpings, we have had no normal puppies that were stillborn or distressed.
So how do you know if your room is dark enough?
If you can see anything at all, that's way too much light. Certainly you cannot be supervising from inside the whelping room. You wouldn't be useful in her very dark den, either.
Check out this graph showing the mortality rate of puppies as a function of time interval between briths Cornellius et al., 2019). The data for the shortest interval was 0-60 minutes. From the rest of the graph it's clear that we would like to have data for shorter intervals than that, because that's where ight level is low enough for no stillbirths. In the graph, I put the data point halfway between 0 and 60 min as the best we could do with the data provided.
Check out this graph showing the mortality rate of puppies as a function of time interval between briths Cornellius et al., 2019). The data for the shortest interval was 0-60 minutes. From the rest of the graph it's clear that we would like to have data for shorter intervals than that, because that's where ight level is low enough for no stillbirths. In the graph, I put the data point halfway between 0 and 60 min as the best we could do with the data provided.
You can use this graph as a very rough guide. If you have a litter of 10 puppies and one is stillborn (10%), that woud correspond to about 30-40 minutes (again, a wild extrapolation of the available data). So 40 minutes - even 30 minutes - between puppies is too long.
Remember, this graph is for stillbirths - puppies that ran out of oxygen and suffocated. Other puppies might also have had experienced inadequate oxygen but were successfully born. Some of these surviving puppies can be expected to suffer from some of the disorders we know to be consequences of hypoxia and oxidative stress in animals and humans. (See Why do newborn puppies die?; and Consequences to puppies of inadequate oxygen during birth)
Also remember that there are other things that might affect the interval between puppies or the risk of stillbirth. We have run into a few of these that were particular to the way the whelping room was set up, so I watch for those when we prepare the whelping room.
If we get everything right, births are 10-20 minutes apart or even less. A litter of seven can whelp in an hour. We have never needed to use calcium between puppies. There are no stillbirths of normal puppies; no puppies needing postnatal assistance. No exhausted mothers.
Now what we need is a cohort of puppies that were whelped without exposure to hypoxia that we can follow through life and record any health issues. The best way to do this is to get a big enough group of breeders together in a single breed so we have enough puppies to be able to compare with those whelped in light.
We have the beginnings of a group for Golden Retrievers, and these puppies will be especially useful because they can be compared to the dogs in the Morris Lifetime Study. If you're a Golden Breeder and want to join, send me a private message.
We welcome any breed where we have enough breeders to produce a decent sample size of puppies for statistics.
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If you would like to learn more about whelping in the dark, see the Facebook group for his project at -
https://www.facebook.com/groups/uterineinertiaindogs
I am also teaching a course about the science behing dark whelping that starts 6 May 2026 ("From Breeding To Weaning: The Critical Role Of Light"). If you wish to participate in the breeding project, you should take this course. Learn more about it here -
https://www.instituteofcaninebiology.org/breedingtoweaning.html
You can learn more about the genetics of dogs in ICB's Online Courses.
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*** Population Genetics for Dog Breeders ***
Visit our Facebook Groups
ICB Institute of Canine Biology
...the latest canine news and research
ICB Breeding for the Future
...the science of animal breeding
