What Are Even-Toed Ungulates?

Even-toed ungulates are animals that belong to the order Artiodactyla. Otherwise known as artiodactyls, they are characterized by having an even number of fingers on their limbs. They are distributed throughout the world except in Antarctica and Australia. Although there are no native species of even-toed ungulates in Australia, they may be found in zoos and other animal reserves.

Fossils of artiodactyls have confirmed their existence 54 million years ago, during the Eocene period. Currently, the order includes 10 families, 86 genera, and more than 220 species. Many of these animals have been domesticated and used for productive purposes by humans. Examples of domesticated even-toed ungulates include cows, pigs, sheep, and llamas.

The study of the evolution of artiodactyls has not provided a specific origin of these types of mammals. According to current research, they appeared around the same time in Europe, Asia, and North America. Although they are present in South America, this is to a lesser extent than in other parts of the world. Learn about what animals are present on this continent with our article on the flora and fauna of the Andean region.

Interestingly, the adaptation strategies of artiodactyls have allowed them to thrive in diverse environments, ranging from arid deserts to lush grasslands, showcasing their incredible evolutionary success.

One of the particularities of artiodactyls is that they are hoofed animals, as are all types of ungulates. While it might seem likely even-toed ungulates have an even number of toes, this is not actually the case. Being referred to as ‘even-toed’ is due to the way they place their weight on their toes when they walk. While it may be what gives even-toed ungulates their name, it is not their only defining characteristic. These include the following:

• They present a paraxonic condition, meaning the 3rd and 4th digits are well developed and their weight is placed on these digits. They can have up to 5 toes, but the others may be vestigial or not there at all.
• In general, the toes are covered by keratin that forms a hoof.
• Most are herbivorous and terrestrial, although there are also omnivorous and semi-aquatic species (with one exception which we explain below).
• Although all mammals have glands, even-toed ungulates are known for having more glands than most which are important for their social and sexual lives.
• The presence of frontal appendages such as ossicones, horns, or antlers is common.
• Most even-toed ungulates have gregarious habits, meaning they live in social cooperative groups.
• The stomach can be simple or with three or four chambers, be ruminant or non-ruminant.
• The upper incisors are usually absent or reduced.

In addition to these characteristics, even-toed ungulates are often recognized for their highly developed senses, which are crucial for survival in the wild. These animals typically have excellent hearing and smell, which help them detect predators and locate food sources efficiently.

Currently, the order Artiodactyla includes 10 MAIN families which are constituted by various different species. Below, we look at the different families of even-toed ungulates and see some examples of each:

• Antilocapridae: includes a single species known as the pronghorn and is endemic to North America. It is an animal similar to the antelope, being a ruminant animal with horns in both sexes.
  
  
• Cervidae: includes the ruminant herbivores known as deer. They have four toes on each leg and bisected hooves. The males have antlers.
  
  
• Giraffidae: made up of only two species of giraffes that inhabit Africa. Both have horns covered by skin that are called ossicones. These are the two little horns which can be seen on a giraffe's head.
  
  
• Bovidae: it is the most numerous group and includes buffaloes, antelopes, gazelles, mountain goats, sheep, goats, and cattle. They are distributed throughout the world and most have been domesticated. They are herbivorous animals and generally both sexes have permanent horns covered in keratin.
  
  
• Camelidae: made up of the herbivorous guanacos, camels, dromedaries, llamas, alpacas, and vicuñas. Their hooves have two toes with strong nails and footpads.
  
  
• Hippopotamidae: here we find the hippos of Africa. They have four toes on each foot and their hooves have soft pads. Their stomach has three chambers, and their incisors and canines are continually growing. During the night they forage in the pastures and during the day they are submerged in water.
  
  
• Moschidae: made up of seven species of musk deer. Unlike the Cervidae, they do not have antlers. They are herbivores and inhabit forested areas and alpine scrub in Asia, especially in the Himalayas.
  
  
• Suidae: includes pigs, wild boars, babirusas, and the warthog. They are omnivorous and ruminant animals found in forests or steppes. They have poor vision, but an excellent sense of smell.
  
  
• Tayassuidae: the family of peccaries, also known as javelinas. They are animals similar to pigs, with an elongated snout and a cartilaginous disc that ends with the nostrils. Their front feet have four fingers and the rear three. The stomach has three chambers and they are not ruminants. They are nocturnal and omnivorous, inhabiting forests and steppes, generally living in groups.
  
  
• Tragulidae: contains ten species of chevrotains, commonly known as mouse deer. They have neither antlers nor horns, but they have four fingers on their limbs and a stomach with four chambers. They are ruminants. Almost all species are herbivorous although some species feed on insects and small mammals.

Although these are the main families of even-toed ungulates, there is another infraorder which needs to be mentioned. They are particularly exceptional due to the fact they do not have toes at all. This is because whales, dolphins, and porpoises from the infraorder Cetacea are also considered Artiodactyla. We know this thanks to investigations using molecular biology during the 1990s^[1].

Due to the discovery of such a close link between cetaceans and other even-toed ungulates, some taxonomists use a different terminology by using the order Cetartiodactyla, rather than Artiodactyla on its own. Others will simply include cetaceans in the order Artiodactyla.

This classification highlights the incredible diversity within the order, demonstrating how evolutionary processes have shaped these animals to suit their respective environments, whether terrestrial or aquatic.

Within the families of artiodactyls that we have named, there are more than 220 individual species. While we have provided some examples in the families above, we want to highlight some more examples indicative of even-toed ungulates:

Gemsbok (Oryx gazella)

This is a large antelope that belongs to the Bovidae family. A distinctive feature is their black mask around a white snout. They inhabit arid plains and deserts, although they can also be found on rocky slopes and dense scrubland. It is herbivorous and they make up groups of 30 to 50 individuals. Both sexes have horns, although those of the female are shorter and thinner.

Guanaco (lama guanicoe)

The guanaco is the tallest mammal in South America and belongs to the Camelidae family. It has long legs and a long neck with a woolly coat. They are a herbivorous species found in open habitats such as steppes, grasslands, and mountains. They are diurnal and gregarious, living in groups of 4 to 20 individuals, where there is usually a single male accompanied by females and young. The young males usually form separate groups among themselves.

Wild boar (sus scrofa)

Within the Suidae family we find the wild boar, an animal with a robust body. Their well-developed tusks grow continuously and curve inwards. They live in areas with good vegetation cover. Their groups consist of approximately 20 individuals made up of females, young, and juveniles. Male wild boars are solitary animals. They are omnivorous, nocturnal, and crepuscular, using their extremely acute sense of smell to locate food.

In addition to these examples, even-toed ungulates play significant roles in their ecosystems, such as seed dispersers and as prey for larger predators, thereby maintaining ecological balance.

Learn about the habitats of some even-toed ungulates with our article on animals that live in temperate forests.

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