Even-toed hoofed animals (Artiodactyla) are the most numerous group of large herbivorous mammals, comprising 220 living species worldwide. Because they mainly feed on cellulose-rich, i.e., hard-to-digest food, they have developed adaptations to a herbivorous way of feeding. Parkljarji do not have continually growing teeth as is typical for rodents, but have raised crowns of their molars to wear down more slowly. Some among them, ruminants, also have a special four-chambered stomach.
For better efficiency, the processing and digestion of food occur in the stomachs of ruminants in a staged manner. Grazed vegetation first goes into a sac-like rumen, which serves as a kind of bag for carrying food. After grazing, ruminants retreat to shelter, where during rest they continue the digestion process. During rest, the food moves from the rumen into the cap, where lumps form. In the chewing phase, the lumps travel back along the esophagus to the mouth, where they are moistened with saliva during thorough chewing. A mushy mass forms, which travels to the third part of the stomach, which we call the nine-lobed stomach. Only from the nine-lobed stomach does the prepared food go to the siriščnik, where it is moistened with digestive juices and is digested with the help of symbiotic organisms.
Herbivorous animals are most exposed to danger precisely during feeding. Small rodents can retreat into burrows to escape predators, while hoofed animals must flee from predators. In escape they rely on speed and agility, hence most hoofed animals have long and slender limbs, with muscular mass concentrated in the body. The elongated bones in the distal parts of their limbs further lengthen them. Parkljarji have developed up to four toes, whose free digits are clad in keratinous hooves. The first toe is missing in all representatives, the second and fifth are more or less atrophied.
Parkljarji living in Slovenia belong to two groups. The first group are pigs with relation (suborder Suina), which in our country are represented by one family, namely pigs (Suidae). The second group of our hoofed animals are ruminants (suborder Ruminantia); we include the deer family (Cervidae) and the Bovidae.
