This image is powerful and instantly relatable: an adorable pet with shining, seemingly tear-filled eyes, looking up at its owner in a moment of distress or sadness. We are a species defined by our capacity for empathy, and in these moments, it is natural to project our emotional reactions onto our animal companions. When we are sad, we cry, so we will definitely cry.
But does a dog, horse or elephant really shed emotional tears – the same saline-and-hormone-laden fluid that flows down a human face in response to intense sadness or joy? The answer, as science currently understands it, is both fascinating and complex, distinguishing between the biological function of tears and the uniquely human expression of emotions.
The Three Types of Tears: A Biological Blueprint
To understand animal “crying”, we first have to look at the biology of tears in the mammalian kingdom. Tears, or lacrimal fluid, are more than just salt water; They are a multilayered, biochemical solution secreted by the lacrimal glands to maintain eye health.
In humans, scientists classify tears into three different types:
- Basal tears: These are produced continuously in small amounts to lubricate the eye, protect the cornea, nourish the ocular surface, and act as a shield against dirt and debris. Basal tears occur in all terrestrial mammals.
- Reflex tears: These are produced in large quantities to flush out irritants such as dust, smoke, foreign objects or fumes from cutting onions. This is a completely physiological, cleansing response, and it is common in many animal species.
- Emotional tears (mental tears): These are produced in response to strong emotional states, including sadness, extreme happiness, frustration, or fear. Importantly, these tears have a different chemical composition than the other two types, containing higher concentrations of stress hormones (such as prolactin and adrenocorticotropic hormone) and leu-enkephalin, a natural pain reliever.
- Scientific consensus: While animals produce basal and reflex tears, the current scientific consensus is that humans are the only species known to shed emotional tears.
🔬 The Uniqueness of Emotional Crying in Humans
Then the question arises: why us? Why did humans develop this distinctive, dramatic and visible way of signaling distress? Researchers believe the answer lies in the interconnectedness of our physiology, our upright posture, and our uniquely complex social structure.
1. The Social Signal Theory
A prominent theory holds that visible emotional tears evolved as a powerful social signal, acting as a silent distress signal.
- Vulnerability and Surrender: Tears blur our vision, effectively turning us into a non-threat. This visual signal of vulnerability may deter aggression in potential adversaries (a concept supported by studies where tears added digitally to human faces were perceived as less aggressive).
- A call for care and empathy: Crying serves as a powerful call for help and comfort, promoting social bonding and eliciting an immediate sympathetic, caring response from others.
- Upright advantage: Unlike many quadrupeds, whose proximity to the ground means distress signals rely heavily on smell and sound, humans rely heavily on visual signals due to our upright posture. A visible tear-streak is an immediate, high-contrast signal from a distance.
2. The Stress Relief Hypothesis
The unique chemical composition of emotional tears suggests a biological mechanism at work. The presence of stress hormones (such as ACTH) and natural pain relievers (leu-enkephalin) in emotional tears has led to the hypothesis that crying is a way for the body to expel built-up stress chemicals and help return the body to a state of homeostasis (balance) after intense emotional arousal. If this hypothesis is true, then emotional tears are literally a waste product of intense psychological distress.
🐕 The Watery Eyes of Our Furry Friends
So, if an animal’s eyes appear wet or watery, what is actually happening?
Tears running down an animal’s face – often called epiphora or tear stains in pets – are almost always caused by functional or medical reasons, not grief.
1. Basal and Reflex Tearing
Like humans, all mammals have a lacrimal system designed for eye health. Excessive production of tears is a sign that this system is reacting to an irritant:
- Foreign objects or irritants: a particle of dust, a piece of grass, or exposure to air or smoke.
- Allergies: Environmental allergens such as pollen or grass can cause excessive tearing.
- Pain or injury: A scratch to the cornea or other trauma to the eye will result in abundant reflex tears.
2. Anatomical and Medical Issues (Epiphora)
In many domestic animals, especially some breeds of dogs and cats, watery appearance is caused by a failure of the drainage system:
- Blocked tear ducts: The tear drainage channels (nasolacrimal ducts) may become blocked or narrow, causing tears to flow down the face instead of into the nose.
- Breed tendency: Brachycephalic (flat-faced) breeds such as Pugs, Bulldogs and Persians are more likely to have structurally shallow eye sockets or compressed tear ducts, making overcrowding common.
- Harderian gland secretion: In some species, like pigs, stress can cause the Harderian gland (a gland often associated with the third eyelid) to secrete a fluid resulting in a reddish bluish appearance, which is sometimes mistaken for crying.
🐘 How Animals Truly Express Grief and Sadness
The fact that animals do not shed emotional tears does not mean that they lack deep, complex emotions. Extensive research confirms that many species, especially social mammals, experience a wide range of emotions, including happiness, fear, anxiety, and profound sadness.
Their emotional communication occurs through various, highly effective evolutionary mechanisms:
| Animal | Emotional Expression (Instead of Tears) | Context for Grief/Sadness |
| Dogs & Cats | Body language (tail tucking, lowered head), vocalizations (whining, whimpering, howling), seeking or avoiding touch, lethargy, loss of appetite, changes in sleeping patterns. | Loss of an owner or companion, separation anxiety, physical pain. |
| Elephants | Prolonged stillness over a body, touching the remains with their trunks, attempting to bury the deceased, making low rumbles, or exhibiting unusual silence. | Death of a calf or matriarch. These behaviors are well-documented and are a strong indicator of grieving. |
| Primates | Huddling, lack of grooming, increased vocal distress, avoidance of play, and exhibiting behavior known as “carrying” of the body for days or weeks after death. | Loss of an infant or close social partner. |
| Cows | Reduced activity, decreased food intake, and the specific use of low-frequency vocalizations when separated from their calves. | Separation from their young. |
The Controversial Dog Study
A recent study published in Current Biology offered a glimpse of the controversy over the consensus. Japanese researchers measured tear volume in dogs using the Schirmer tear test and found that tear production increased significantly when dogs were reunited with their owners after a period of separation compared to reuniting with a familiar, non-owner human.
The researchers speculated that this increase might be linked to an increase of oxytocin (bonding hormone) upon reunification, suggesting a possible – albeit very mild and functionally distinct – link between emotions and tearing in dogs. However, this finding is considered preliminary and remains controversial, with many scientists arguing that fluctuations in tear volume may be caused by environmental irritants, excitement, or other factors unrelated to human-like grief.
The Verdict: Tears of Function, Not Tears of Sorrow
Do animals shed tears when they are sad?
No, not in the human sense.
While a creature’s eyes may glaze over with fluid, that overflow is a physiological response to irritation, anatomic changes, or an overactive drainage system. They have the biology of tears (basal and reflex), but they lack the unique neurological and social-evolutionary connection between strong psychological emotion and the secretion of chemically distinct tears that is a hallmark of the human experience. Ultimately, the lack of human-like crying does not diminish the depth of an animal’s emotional life. It simply reinforces a profound lesson in biology: emotion is universal, but the language used to express it – whether through a silent tear, a mournful trumpet, or a low arched tail – is uniquely adapted to each species’ life and environment.
