Even in the animal world, personal hygiene is a regular daily obligation
Few animals (unlike humans) are in a hurry to remove a strong or unpleasant odor from their body. On the contrary, some animals often deliberately soil themselves to cover a trail and deceive the enemy. This does not mean that personal hygiene is unknown to them. We know that dogs and cats spend a lot of time a day licking their own bodies. Wild animals do this too, not for beauty and appearance, but for practical and health reasons. They often have help with this daily hygiene ritual.
Fur and feathers retain a layer of air that regulates body temperature. This layer of air is only effective if the hair and feathers are in perfect order. This is reason enough for daily hygienic cleaning.

1. Birds’ feathers should be clean and tidy so that they can fly unhindered every day. Swamp birds’ feathers should even be oiled (from the fat secreted by a gland under the feathers). That’s why birds spend hours cleaning and grooming.
2. Animals sometimes need to use means completely opposite to the concepts of hygiene and cleanliness (to remove bacteria and animal parasites). One example is elephants rolling in mud or dust.
3. Many monkeys, for example, mutually clean and groom each other and mutually remove parasites and other impurities from the body (fur.
4. Some animals have assistants when performing hygiene. Aids are usually of other types. Tropical crabs (and many types of fish) feed on larger fish, close and distant marine relatives – they clean their skin of parasites.
5. And many African birds live from the great preparation of their large (often dangerous) compatriots.
6. Rhinoceros, zebra, bison and other ungulates have some types of birds that maintain hygiene behind their ears, nostrils and intimate parts of the body. Thus, these types of birds remove parasites, ticks, fleas and other unwanted insects from the skin of bison, zebra, rhinoceros and other ungulates.
7. There are also animals (some types of birds) that clean even the terrible jaws of crocodiles from the remains of food without the slightest fear.

https://www.dkfindout.com/us/animals-and-nature/horses/zebras/