I know that some animals treat simple injuries by licking them. Are there any animals that, like humans, treat each other鈥檚 injuries, and do any animals have more sophisticated forms of 鈥渕edical treatment鈥�?
鈥� Licking each other鈥檚 and their own wounds is the most common form of wound treatment for mammals. It is believed that such behaviour dates from the earliest days of mammals. Saliva generally is germicidal and benefits wound tissue, causing little harm to live tissue while helping to slough off or recycle dead tissue.
The habit no doubt developed out of a defensive response to the pain, plus an eating response to bodily fluids and detritus. In fact, when mothers of many species lick sick cubs, if there is no improvement, it can lead to them eating their babies. Distressingly, such disruption may also lead the mother to eat the rest of the litter, especially if they are very young.
Advertisement
Formal hygiene and treatment of illness and injury, especially of other individuals, is mainly a human behaviour. However, it depends on what you choose to call 鈥渢reatment鈥�. Candidate activities among birds include dust-bathing, hiding and resting when ill, and 鈥渁nting鈥� 鈥� where they rub their feathers with ants, which then secrete antimicrobial chemicals. Various birds and mammals eat clays to counteract poisons in food, and some types of chimpanzees chew certain pungent leaves when ill. Such 鈥渕edicines鈥� may control parasitic worms. Since plants and traditions vary by region, those habits clearly get passed on as learned knowledge.
鈥淪ome chimpanzees chew pungent leaves when ill, possibly to counter parasites鈥�
Jon Richfield, Somerset West, South Africa
鈥� Saliva contains a complex cocktail of enzymes, many of which have antibacterial properties. In addition, it contains epithelial growth factors that promote healing in the wound; and the act of licking will tend to debride and remove gross contamination from the affected area. At the same time, saliva contains huge numbers of various bacteria. Fortunately these are largely beneficial or have no effect, and there is no evidence to suggest they are detrimental to wound healing.
D. L. Harris, By email, no address supplied
Peruvian macaws are known to eat clay from river banks in behaviour known as . Animals and birds are often observed behaving in this way, but this is usually to provide grits for grinding food in their gizzards or supplying essential minerals to their diet. The macaws, however, consume only one particular type of clay which is low in biologically relevant minerals and also far too fine to exert crushing and grinding effects on food in the gizzard. Instead, the birds were self-medicating to protect themselves from poisons. The clay is positively charged, and in the birds鈥� stomachs it binds to negatively charged toxic alkaloids that the birds have ingested from unripe fruit and seeds. This protects the parrots from the effects of the alkaloids, while giving the macaws an ecological advantage over other animals and birds which cannot consume the same unripe foods.
鈥淧eruvian macaws eat clay from river banks to protect themselves from poisons in their food鈥�
Patrick Walter, London, UK
鈥� Water buffaloes submerge themselves to cool off when it is hot, and many animals such as elephants roll themselves in mud or soil to gain a protective coating. More specific 鈥渕edical鈥� treatments are known: primates delouse their friends and kin, and it has been reported that ill chimpanzees and gorillas seek out and eat various plants that are effective against parasites, joint pains and other conditions. Some apes gnaw willow bark to reduce pains such as toothaches, just as humans first discovered and made use of acetylsalicylic acid (aspirin) in the same way in ancient Greece and medieval England.
Bart Holland, New York, US