Dog owners are endlessly fascinated by the many abilities their extraordinary companions possess. We also like to compare them to ourselves. The difference between canine and human scenting ability or dog years to human years for example that we compare to. So how about what they see during the night?
Dogs Seeing At Night
How well dogs see in the dark, and what they see, is one of those topics dog lovers often ask about.
The first place to start is to understand what dogs were evolved to do. Their functions of their eyes and how it influences their vision. As natural predators, dogs are (or were) nocturnal hunters. The wild canines that our pet dogs evolved from are “crepuscular,” meaning they are active primarily at dusk and dawn. They needed to be able to spot movement in dim light in order to track and catch their dinner (or breakfast).
The Structure of the Canine Eye
To make it possible to navigate in the dark, the canine eye has a larger pupil than a human’s. In the anatomical structure of the eye, the retina has light-sensitive cells, called rods, which help an animal or human see in low light. Dogs have more of these rods than we do. The retina also has cones, and they determine which colors dogs can see.
An animal’s ability to see in the dark is also influenced by Flicker Fusion Frequency (FFF) (or threshold). This is the frequency at which flickering light no longer appears to flicker (meaning it appears as a constant illumination). Generally speaking, the faster a species moves through its environment, the higher its FFF. But a dog’s secret weapon in their ability to see in the dark is the part of the canine eye called the tapetum lucidum. The tapetum acts as a mirror within the eye, reflecting back the light that enters it, and giving the retina another opportunity to register the light. So, dogs can see in the dark, and other low-light situations, better than humans.
Why Do Dogs’ Eyes Glow in the Dark?
You’ve no doubt seen that eerie, greenish-yellow glowing look of a dog’s eyes when light hits them at night, such as from headlights or a flashlight, and in photos (caused by the camera flash). What you’re seeing comes from the tapetum.
The shiny surface of the tapetum bounces any light that has not been caught by the photosensitive cells back up to the retina, thus giving the photoreceptors a second chance at catching the dim light entering the eye.”
But the tapetum actually does even more: it amplifies that light through a phenomenon called fluorescence. This not only adds to the light’s brightness but it also slightly changes the color of the light that is reflected back. The color shift moves the wavelength of the light closer to that to which the rods are most sensitive to and can best detect. And the tapetum reflects up to 130 times more light than the human eye. This is why dogs are five times more sensitive to light that we are.
Most dog breeds have about 250 degrees of field of vision
Adding to dogs’ special ability to see in the dark is their increased field of vision. Compare that to ours, which is about 190 degrees.
If you are a dog owner, then you surely understand that your canine has feelings. And research increasingly supports the view that dogs experience a range of emotions. But do dog eye tears really mean they are sad?
A study in 2016 showed that dogs are able to recognize emotions not only in other dogs but in humans too. In addition, many dog owners share stories about their dogs trying to comfort them when they are crying or upset.
Excitement, fear, love and anger are some emotions that your dog is likely to feel.
When trying to understand your canine’s emotional range and figuring out their overall health needs, you may wonder whether your dog feels sadness and cries like a human.
You also may be curious whether they cry due to pain or illness.
Keep reading and we’ll discover whether dogs feel sad and if they shed real tears.
Do Dogs Feel Sadness?
Unlike humans, dogs become emotionally mature early and have an emotional range equivalent to a two- to two-and-a-half-year-old child.
If you are familiar with toddlers, then you certainly know that they cry. Like a toddler, dogs feel emotions like fear, distress, anger, and suspicion.
These emotions are related closely to sadness. However, more complex emotions like shame and guilt never develop in dogs. So, dogs do not feel sadness quite like humans do.
Despair, remorse, depression, dejection, and misery are a few words that you might use to describe your own sadness. But when it comes to your dog, stress, discontentment, and uneasiness are better descriptors.
Do Dogs Cry When Sad?
When a dog is sad, you may see telltale signs that it is upset.
According to the American Society for the Prevention of Cruelty to Animals (ASPCA), canines have specific types of body language that can tell you how they are feeling.
While body language may not directly indicate a specific emotion, it can tell you if your dog is content, scared, or feeling aggressive.
Relaxed features indicate contentment. When relaxed, your dog’s mouth will be slightly open with the tongue out, and it may be panting. Its eyes may almost seem to be squinting, and the ears and tail will be in neutral positions.
Fear or Stress Face
In the case of fear or stress, your dog may take a submissive posture. Eyes will be partially closed, the ears will be pinned back against the head, and the tail will be between the legs. You may also see the mouth closed and the snout angled toward the floor.
It may seem as though your dog is cowering in front of you.
Dog In Distress
When your dog is in distress, you may notice some vocalizations.
Stress vocalizations include high-pitched barks, whimpering, and yelps. Yelps, whines, and whimpers may also indicate that your dog is experiencing pain. A dog in pain is more likely to growl or bite, so use caution if you think your dog might be suffering.
Dogs Mimic Humans
In some cases, you may even notice your canine companion mimicking human words or sounds. This is a common tactic your dog may use to show affection if you have reinforced this behavior.
While all of these things may be noted, there is one thing you will not see—your dog crying tears.
Can Dogs Cry Tears?
You may want to know, can dogs cry? Yes, dogs can shed tears.
However, they do not cry in the way we do in response to emotion. To understand dog eye tears and crying, it may help if we take a look at how a dog’s eyes are constructed.
Dogs have the same basic eye structure as other mammals. The cornea, lens, conjunctiva, and sclera make up the different tissues within the eyeball, just as they do in our eyes.
The eye sits in the orbit—or eye socket—and is protected by the upper and lower eyelids.
The tissues of the eye need to be kept moist. Moisture lubricates the tissues so the eyes can move smoothly in the socket and the eyelids can glide over the eyes.
We all know how uncomfortable dry eyes can be, and it’s the same for dogs.
Moisture also helps to wash away grit and debris that can scratch the sensitive surface of your dog’s eye.
Humans have a fairly simple lubrication system that involves the secretion of fluid from glands. They are called lacrimal glands, tear glands to you and me, and each eye has one.
These glands release fluid that is then forced over the surface of the eye with the help of your eyelids.
Do Dog Eye Tears Differ from Human Tears?
Yes, our dog’s tears are different from ours. Dogs have much more complicated lubrication and eye moisture systems.
First, canines have a third eyelid located in the inner portion of the lower eyelids. This third eyelid, or nictitating membrane, is a clear structure that moves over the eye to protect it. It also moistens the cornea while maintaining vision and produces lymph fluid that helps prevent infection
Dogs also have three types of glands that provide moisture for the eyes. These glands work together to produce the moisture your dog needs to keep its eyes healthy and functioning properly.
They are the lacrimal glands, like humans have, the meibomian glands and mucus glands. The lacrimal glands create watery tears, the meibomian glands produce an oily tear while the mucus glands produce mucus.
When your dog blinks, these three are mixed together. This creates a thicker fluid that takes longer to evaporate and offers better protection to the eyes.
Is Your Dog Crying Tears?
No, your dog isn’t crying tears of sadness. Dogs do not cry when they are sad.
In fact, humans are the only beings that cry. According to Scientific American, humans even stand out against other primates as the only animals that cry emotional tears.
So, what is going on if you see dog tears? Well, it is likely an issue that requires the assistance of your veterinarian.
In medical terms, the excessive production of tears is called epiphora.
Epiphora is a medical condition that can be caused either by disease or a congenital disorder. In the case of a congenital disorder, your dog may be predisposed to watery eyes due to the shape of its face, particularly the eyes and nose. Excessive tears may cause red or brownish stains.
Congenital epiphora conditions are most commonly caused by the turning in of the eyelashes, the folding inward of the eyelids, or the bulging of the eyes themselves.
Labrador Retrievers, Cocker Spaniels, Bulldogs, Pugs, and Mastiffs are just a few breeds that are prone to these sorts of issues.
Other symptoms of epiphora include:
crusting or discharge
eye sores or ulcers
loose or inflamed skin around the eyelids
If your dog is exhibiting these symptoms, speak with a veterinarian as soon as possible. Treatment should be provided right away so your dog feels as comfortable as possible.
Treatment may be as simple as applying a topical medication daily or as complicated as corrective surgery.
What Causes Dog Eye Tears?
If not caused by a congenital issue, a medical issue may be causing the eyes to water excessively.
The following conditions may result in excessive tearing:
foreign matter or debris in the eye
sinusitis or acute sinus infections
tear duct obstructions
In order to diagnose the cause of epiphora, your veterinarian may need to use imaging tests to find the problem.
Specifically, X-rays may be needed to find eye abnormalities. Imaging and visual examinations may be done with contrast dyes to help your veterinarian distinguish the structures of the eye.
In situations where simple tests cannot be used to locate the issue, the veterinarian may order blood tests, MRIs, or CT scans. In cases where a serious issue is suspected, but cannot be positively identified, surgical exploration may be required.
Dog Eye Tears – Summary
Dogs produce excessive tears from their eyes in response to injury or infection or due to inherited problems with their facial anatomy.
Dogs don’t cry tears in response to emotions, such as sadness or fear, or when they are in pain.
That doesn’t mean that dogs don’t feel emotions. On the contrary, recent research shows that dogs experience and understand a range of emotions. Learning how dogs display their emotions through body language can help us understand them.
If your dog is producing excessive dog eye tears, they are likely to be sore and uncomfortable, so do get it checked out by a veterinarian as soon as possible.
Behind the Door at the Vet
I have worked in the veterinary field for many years and have seen plenty of dogs that come in because they are crying and have something going on with their eyes. The first thing the vet will do is look into their eyes with a light to make sure their pupils are dilating correctly and see if the retina is still attached to the back of the eye. Next, they will stain the eye with fluorescein be sure there are no scratches on the cornea.
If the eye is bad enough, the vet might suggest surgery to remove the eye if nothing has worked. Dogs are very resilient and this only effects their depth perception and not seeing peripheral vision on that side.
Albuquerque N, Guo K, Wilkinson A, Savalli C, Otta E, Mills D “Dogs recognize dog and human emotions” The Royal Society 2016
Morris P, Doe C, and Godsell E, “Behavioural reports and subjective claims by animal owners” Journal of Cognition and Emotion 2007