No, humans are not the only animals that cry, but the distinction depends entirely on which tears you mean. Only humans reliably produce emotional tears, the weeping that follows grief or joy. Many other mammals shed basal and reflex tears to lubricate their eyes and flush irritants. Ape and elephant studies hint at something closer to emotional crying, yet no nonhuman animal has been confirmed to weep from sadness the way people do.
Three Kinds of Tears and What Each One Does
Tear science starts with a classification that most pop explanations skip. Tear film has three layers, and each layer has a job.
Basal tears are the continuous secret. They coat the cornea in a film roughly 7 micrometers thick and flow at about 1.2 microliters per minute during waking hours. This film carries oxygen, washes away debris, and keeps the surface smooth enough to refract light.
Reflex tears respond to a trigger. A speck of dust, a sliced onion, or a blast of cold wind stimulates the trigeminal nerve, and the lacrimal gland floods the eye in under a second. These tears are watery and low in protein.
Psychic tears, also called emotional tears, follow a feeling rather than a physical stimulus. They contain higher concentrations of protein, prolactin, and the hormone ACTH than reflex tears do. The body routes them through the same lacrimal gland, but the signal arrives from the limbic system rather than the eye surface.
In plain terms: every mammal with a lacrimal gland can make the first two types. The third type is where the species boundary gets interesting.
The Lacrimal System: Plumbing Shared by Nearly All Mammals
The hardware for crying evolved long before the behavior. Nearly every land mammal has lacrimal glands above the outer corner of each eye and a drainage channel called the nasolacrimal duct that empties into the nose.
That duct explains a familiar sensation. When you cry hard, tears spill down the duct into the nasal cavity, which is why a good sob produces a runny nose. The same anatomy means reflex tears drain efficiently, while emotional tears produced faster than the duct can handle spill onto the cheeks.
Rodents, dogs, cattle, and primates all carry this plumbing. Seals and whales have modified tear systems suited to salt water. The machinery for making tears is close to universal among mammals, roughly 5,400 species. The machinery for crying from emotion is not.
Which Animals Actually Shed Tears in Response to Feeling
The evidence splits into three tiers, and the tiers carry very different weight.
Tier one, reflex and basal tears, is established for virtually all mammals. A 2023 study in the journal Animals found that domestic dogs produce reflex tears when reunited with a familiar person, with tear volume rising measurably after separation and return. The authors proposed oxytocin as a driver. This is reflex-adjacent crying tied to arousal, not proof of sorrow.
Tier two, distress vocalization with wet eyes, appears in many young mammals. Puppies whimper with watery eyes. Elephant calves in distress produce tears and vocalizations together. The tears here may be reflex responses to facial muscle tension rather than an emotional signal.
Tier three, weeping from grief, is the rarest claim. Reports of elephants mourning dead herd members with visible tears circulate widely, but controlled measurement is scarce. A 2011 review of animal emotion in the journal Applied Animal Behaviour Science cautioned that most such accounts are anecdotal.
The Cry Comparison: How Species Stack Up
The table below sorts animals by the strongest evidence for each tear type. Confidence reflects peer-reviewed measurement, not folk reports.
| Species | Basal tears | Reflex tears | Emotional tears | Strongest evidence |
|---|---|---|---|---|
| Humans | Yes | Yes | Yes, routine | Established; onset around 3 to 4 months of age |
| Chimpanzees | Yes | Yes | Possible, rare | Anecdotal weeping reports; limited lab data |
| Elephants | Yes | Yes | Contested | Anecdotal mourning accounts; no controlled study |
| Dogs | Yes | Yes | Unlikely | 2023 reunion study measured reflex tear rise |
| Rats | Yes | Yes | No | Reflex tears documented; no emotional link |
| Camels | Yes | Yes | No | Heavy reflex tearing from dry, dusty habitat |
| Sea turtles | Yes | Yes | No | "Crying" is salt excretion, not emotion |
The camel case matters. Camels are famous for crying, but the tears are largely a response to blowing sand and dry air, plus a need to excrete excess salt. The sea turtle is a cleaner example. Turtles "weep" to shed salt through glands near the eye, a process called osmoregulation. No feeling is involved.
Why Emotional Crying May Be Uniquely Human
Emotional tears appear to require three things stacked together: a large prefrontal cortex, complex social bonds, and a face built to signal. Humans have all three in unusual combination.
The leading hypothesis treats crying as a social signal. Visible tears tell others that the crier needs help and is not a threat. A 2016 study in the journal Emotion found that tears reduced observers' willingness to aggress against a face, and lowered testosterone in male viewers by a measurable margin. Crying, in this frame, is communication, not just release.
Ape anatomy offers a partial match. Chimpanzees have lacrimal glands and facial muscles close to human arrangement. Jane Goodall reported weeping in chimpanzees, but those accounts lack the tear-volume measurement modern studies use. The honest position is that ape emotional tears are plausible but unconfirmed.
Common Misconceptions About Animal Crying
Several popular claims collapse under scrutiny.
The first is that all animal tears mean sadness. Reflex tears from onions, dust, or wind are the majority of nonhuman tearing. Attributing grief to a tearing dog or horse is a category error unless arousal and context are controlled.
The second is that crocodiles cry while eating prey. The phrase "crocodile tears" traces to a belief that crocodiles weep as they devour a victim. The real behavior is simpler: a crocodile eating a large meal forces air and pressure through the mouth and sinuses, which can push tears out of the eye. It is anatomy, not remorse, and the term now describes insincere grief.
The third is that emotional tears are just reflex tears with feeling added. They differ chemically. Emotional tears carry more protein and stress hormones, and a 2011 study in the journal Evolutionary Psychology found they also contain nerve growth factor at higher levels than reflex tears.
Do Emotional Tears Carry a Chemical Signal?
A newer line of research argues that tears send chemical messages, not only visual ones. A 2023 study published in PLOS Biology found that human emotional tears, when sniffed by men, reduced brain activity in regions tied to aggression and lowered aggressive behavior in a lab game.
If that finding holds, crying is a dual-channel signal. The wet eyes say "I need help" to the eye, and the tear chemistry says "stand down" to the nose. No nonhuman species has been shown to use tears this way, though the study is small and the mechanism is far from settled.
The Timeline of a Human Cry and How It Compares
The table below traces a single emotional cry from trigger to recovery. The right column contrasts what a nonhuman mammal does at the same stage.
| Time point | What happens in a human cry | Nonhuman mammal comparison |
|---|---|---|
| 0 seconds | Limbic trigger fires; lacrimal gland receives signal | Reflex trigger only, from eye irritation |
| 1 to 3 seconds | Tears begin; volume rises across the first minute | Reflex tears rise in under a second |
| 30 to 60 seconds | Protein-rich tears flow; breathing deepens | Tearing peaks and plateaus |
| 1 to 3 minutes | Sobbing and facial expression peak | No comparable vocal-emotional sequence |
| 3 to 10 minutes | Tear flow slows; heart rate eases | Tearing stops once the trigger clears |
| 10 to 20 minutes | Mood shift, often calm or drained | Return to baseline behavior |
| Hours | Emotional afterglow; social effects linger | No documented afterglow |
Most human cries last 1 to 20 minutes. Infants cry far longer, up to several hours per day in the first months. That duration has no clear nonhuman parallel.
What to Actually Do With This Knowledge
This is not a topic that calls for medical action, but a few practical points help pet owners and curious readers.
- Do not read grief into a pet's tears. A tearing dog is more likely reacting to dust, wind, or arousal than to sadness.
- Check for eye problems when tearing is one-sided or constant. Excess reflex tears can signal a blocked tear duct, an ulcer, or an infection, and warrant a vet visit.
- Distinguish reflex from emotional tears in yourself before assuming the worst. Onion tears and grief tears feel different and carry different chemistry.
- Treat animal mourning reports with calibrated respect. They may reflect real distress, but visible tears are weak evidence on their own.
In plain terms: crying is plumbing almost everywhere and feeling in very few places.
Limits of the Evidence and Open Questions
The field has real gaps. No study has measured tear chemistry during a nonhuman animal's apparent grief, largely because collecting tears from a distressed elephant or ape is difficult and ethically fraught. That means the emotional-tears question for animals rests more on observation than on lab data.
The human studies also carry caveats. The 2023 aggression study used small samples and a single population. The 2016 aggression finding has been replicated, but effect sizes are modest. Crying research is young, and certainty should match that.
What is clear is the boundary. Humans are the only species confirmed to cry from emotion, with reflex and basal tears shared across thousands of mammal species. Apes and elephants may sit close to the line, and the next decade of measurement, especially tear chemistry in great apes, could move that line one way or the other.