Many animals exhibit wound licking behavior as a way to clean and treat injuries. Wound licking likely evolved as an adaptive behavior to promote healing and prevent infection in animals. When an animal licks a wound, the saliva can help clean away debris, bacteria, and dirt. Additionally, saliva contains compounds that have antimicrobial, analgesic, and tissue healing properties. Several common domestic and wild animals are known for licking wounds, though the extent and purpose of this behavior can vary by species.
Dogs
Dogs frequently lick wounds on themselves and other dogs. Their saliva contains chemicals such as lysozyme and peroxidase that have antibacterial properties to clean wounds. There is also evidence that dog saliva stimulates tissue growth, as licking encourages blood flow to the wound site. Vets may recommend use of an Elizabethan collar to prevent a dog from excessively licking surgical incisions. However, licking is an innate self-soothing behavior for dogs, and light wound licking can be beneficial.
Cats
Cats also exhibit wound licking behavior, though not as commonly as dogs. Cat saliva has antibacterial compounds like lysozyme, as well as cytokines that can accelerate wound healing. However, cats also groom themselves extensively for coat maintenance. Excessive licking around a wound site can delay healing and cause skin irritation. Cats may need an Elizabethan collar to prevent over-grooming of injuries. But light licking that cleans debris from the wound can aid the healing process.
Horses
Horses will naturally lick lightly at wounds on their own bodies as a first line of defense. A horse’s tongue can effectively remove dirt and debris to help clean the area. Saliva on the wound forms a protective coating. Horse saliva also has histatins that inhibit bacterial protease enzymes. However, too much licking can slow healing. Horse owners often apply ointments to wounds to dissuade excess licking, or use bandages if needed. But horses do benefit from an initial period of licking right when the wound occurs.
Rodents
Wild rodents like rats and mice will lick at their wounds as an instinctive cleaning behavior. Their saliva releases tissue growth factors that activate wound healing pathways. In a study of mice, self-licking enhanced wound closure compared to wounds that could not be licked. There is also evidence that rodent mothers will lick the wounds of their pups to clean them and stimulate tissue regeneration. Pet rodents can likewise benefit from some wound licking depending on the severity of the injury.
Bears
Bears have been observed licking their wounds after fights with other bears or predatory close calls. Their saliva contains biological compounds that aid wound healing. And since bears cannot easily tend to their own injuries, licking allows them to clean out bacteria and debris. For severe injuries like infected fight wounds, licking may not be sufficient, putting the animal at risk of decline or death. But for mild scratches and cuts, bears appear capable of cleaning and healing minor wounds through licking.
Deer
Deer use their tongues to lick lightly at their wounds, which cleans out dirt and applies antimicrobial compounds. Deer saliva contains tissue growth factors that promote wound repair. Mother deer will also lick the wounds of fawns. For significant injuries, deer may continue licking to the point of rubbing a wound raw. But for mild incisions, scrapes, and punctures, licking benefits the healing process for deer if not done excessively.
Cattle
Cattle lick wounds as a natural cleaning instinct, including licking the injuries of herd mates. Cow saliva has lysozyme, lactoperoxidase, histatin, and other compounds with antibacterial activity. Licking helps remove debris while also applying antimicrobial enzymes. However, cattle do not distinguish between light beneficial licking and excessive abrasive licking. Cattle owners often apply antibiotic ointments and wrap larger wounds to stop cattle from rubbing a wound raw through over-licking. But for mild cuts, some licking can promote healing.
Primates
Many primate species including monkeys, lemurs, and apes will lick wounds on themselves or others in their social group. Their saliva contains factors like peroxidase that fight bacteria. Primates will often focus on licking the wounds of their offspring. Wild primates have been observed to lick severe injuries to try to clean out infection, sometimes to beneficial effect. Zookeepers may need to bandage wounds on primates to limit potential over-grooming. But research suggests primates innately understand the healing properties of saliva, and will concentrate on licking their worst injuries.
Rabbits
Rabbits will lick relatively mild wounds on their bodies as an initial cleansing instinct. Their saliva can remove debris and has some antimicrobial factors. However, rabbits have a natural instinct to hide illness and are prone to over-grooming wounds until they become inflamed or infected. Rabbit owners need to monitor wound licking closely, and wrap or bandage injuries as needed to prevent worsening from excessive licking. So while rabbits do exhibit wound licking behavior, their saliva compounds lack potency, and their grooming tendency requires intervention for wounds to properly heal.
Amphibians
Certain amphibians like salamanders will secrete serous fluid from their bodies onto their wounds as a form of licking. The fluid contains active compounds that have antibacterial properties. Frogs may likewise rub their limbs over wounds to apply the bioactive compounds secreted through their skin for an antimicrobial effect. And tadpoles appear to benefit from their mother’s licking of surface injuries, with an improved healing rate compared to untouched wounds. So while not exactly licking, some amphibians demonstrate a similar wound cleansing instinct.
Reptiles
Most reptiles do not actively lick their wounds. Some exceptions include tortoises, which will slowly lick minor shell injuries to clean them as the shell heals. Occasionally lizards may rub their tongue over a small wound, but not for any major benefit. Snakes flick their tongue in the air to sample scents but generally do not purposefully lick injuries. Overall reptiles do not exhibit strong wound licking behavior, likely as their blood has natural antibacterial activity, and their outer skin prevents contamination.
Birds
Parent birds are well known for licking the wounds and sores of baby chicks in the nest. Their saliva can clear out infections and promote healing. Pet birds like parrots may pick at their own wounds but do not lick them. The structure of most bird mouths prohibits effective self-licking. Still, licking wounds of offspring is an important part of nest hygiene for parent birds to prevent infection from setting in. Birds are a prime example of social wound licking in the animal kingdom.
Insects
Some insects like honey bees will perform wound licking on members of their colony. When a bee is injured, other worker bees will gather around and rapidly flick their mouths over the wound. Their saliva has glucose oxidase which releases hydrogen peroxide for an antimicrobial effect. Termites also secrete antimicrobial fluids onto wounds through their mouths. Social licking behavior allows insect colonies to prevent infectious outbreaks.
Aquatic Animals
Marine animals generally do not exhibit wound licking behavior. The ocean water may actually irritate and infect injuries further. However, dolphins are an exception, as they will gently rub their teeth and jaws over wounds on themselves or other dolphins. Dolphin saliva may have antimicrobial properties from their fish diet. The intelligence of dolphins also suggests they understand the benefits of wound licking through learned experience.
Conclusion
In summary, wound licking is an adaptive behavior seen in many species of mammals, birds, and insects. Licking applies antimicrobial compounds while removing debris to spur healing. Dogs, primates, horses, bears, cattle, and rodents all instinctively lick injuries on themselves or others. Parent birds lick the wounds of chicks to prevent infection. And eusocial insects use colony licking to protect against outbreaks. However, excessive licking can delay healing, so bandages are sometimes needed. Overall, the natural cleansing properties of saliva make wound licking a common healing behavior across the animal kingdom.