Animals take medication of their own free will without the intervention of a vet or their caretaker. There are many examples. They might eat it or apply it topically. The long, indigestible word “zoopharmacognosy” is an amalgamation of several roots of words: zoo meaning animal, pharma meaning drug and gnosy meaning knowing.
For cats, two examples come to my mind. There are probably other examples.
The first is eating grass. I think there is still some uncertainty as to why domestic cats eat grass. Some say it is to make themselves sick to remove hairballs or anything else in their gut which is causing discomfort. Other theories are that it acts as a laxative so that hairballs are passed.
Dr Morris believes the reason is to ingest folic acid in the grass. Folic acid is a vitamin used in the production of haemoglobin, which carries oxygen in the blood. When cats chew on it they ingest folic acid released from the grass and improve their capacity to transport oxygen around their body thereby improving health generally.
Perhaps the habit goes back to the need of the wildcat ancestor to maximum oxygen intake so as to be able to run at peak performance when hunting prey but I am speculating.
The snow leopard goes further and eats a bush (Myricaria bushes) which I theorise is necessary to once again improve oxygen intake which is vital when hunting and living at high altitude. The bush eating snow leopard is a refinement on the grass eating domestic cat. This cat also eats Tamarix twigs. The quantities are not small and form a significant part of the diet.
Dogs also eat grass. It is believed they do it to remove stomach irritation by making themselves sick. Dogs can’t digest grass well. Dogs eating grass have been found to be suffering from bowel diseases and inflammed stomachs.
Cimpanzees eat the leaves of the Aspilia plant to treat and kill certain internal parasites. Apes have some knowledge of medicine. They select a part of a plant that they know is a treatment (I don’t know what for though) and take of the leaves and then break the stem to suck the juice.
Some bird species roll in ants especially those that spray formic acid as formic acid is harmful to or kills feather lice.
The goat appears to be a very competent self-medicator. Their activities include licking a wall in the Gran Paradiso National Park in Northern Italy for minerals and salts.
There are many other examples which I won’t cover here.