General characteristics of ungulates

1. General Characteristics of Ungulates
1) Hooves – Most ungulates have hooves. Hooves are composed primarily of keratin. Some
ungulates, such as camels, rhinos, and hippos, do not have hooves, but have foot pads and
‘nails’. 2) Diet – Most ungulates are herbivores – meaning they eat primarily plant material.
(Exception – Pigs are omnivores. They eat a wide variety of foods. They have (“simple”
stomachs.) Ungulates that are herbivores may be referred to as grazers or browsers. Grazers
eat primarily grass. Browsers eat various parts of other types of plants such as trees and
bushes. Browsers may also eat some grass.
3) Digestive system – The digestive system of ungulates (expect for pigs) is specialized for
drawing nutrients from plant materials. Microbes (bacteria & protozoa) that live in the
animals’ digestive systems can break down cellulose. The cellulose then undergoes
fermentation and is converted to substances that the body can use to build protein,
carbohydrates, and fat. The ability to break down cellulose and convert it to usable products
makes these animals unique among mammals (colobus monkeys are also able to do this).
(See the information under each Order for more details.) Many ungulates do not have a gall
bladder. The gall bladder is “the source of bile salts that emulsify and break down fats”.
Since plant material contains little fat, the ungulates do not need a gall bladder. (Macdonald
pg. 469)
4) Teeth – Most of the ungulates* have teeth that are specialized for eating plant material.
Their
incisors (teeth in the front of the mouth) are adapted for plucking plant material. They have
large molars that are flat and square. The cheek teeth of many ungulates are adapted to
undergo a lifetime of constant wear from grinding plant material. Most ungulates (except
pigs and peccaries) have high crowns that wear down over time.
The jaw joints and jaw muscles of ungulates are modified so that their jaws can move
sideways, rather than just up and down. This allows them to maximize the side-to-side
grinding action needed to break down plant material. (See the information on the following
pages for details on teeth.)
The term ungulates (“UN-gyuh-luts”) refer to animals with hooves. Ungulates
include 2 orders of mammals. The 2 orders are named based on the number of “toes” or
hooves that they have per leg. The word “Perissodactyla” (“pe-RIS-so-dak-‘ti-la”) is
derived from the Greek words “perissos”, meaning odd, and “dactylos”, referring to the
toe. The Perissodactyla order includes the rhino, horse, and tapir families. Rhinos have 3
hooves per foot; horse – 1 hoof; and tapirs –3 hooves. The word “Artiodactyla” (“ARtee-o-dak’-
ti-la”) comes from the Greek words “artios”, meaning even, and “dactylos”,
referring to the toe. The Artiodactyla order includes the camel family (2 toes), the hippo
family (4 ‘toes’ present within each of their legs) and the cloven-hooved (2 hooves)
animals – cattle, sheep, goats, antelope, etc. 2
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2. Order – ARTIODACTYLA
(Even-toed ungulates – cattle, sheep, goats, deer, camels, pigs, etc.)
Digestive systems
• Non-ruminants
Pigs have “simple” stomachs. Their digestive systems are similar to humans and they
produce similar digestive enzymes.
Peccaries have a chambered stomach “in which it is thought microbial flora digests
cellulose, as occurs in ruminants” *(Macdonald 504). “The stomach is complex, with two
sausage-like cul-de-sacs. There is no gall bladder.” (Fowler 966) However, peccaries are
not classified as ruminants because they do not chew their cud.
Hippopotamuses also have chambered stomachs, but they too, are not ruminants.
• Ruminant (4-chambered) digestive system
Ruminants have 4-chambered stomachs. Ingested food first passes to the first
chamber, the rumen. The rumen is the primary site of cellulose breakdown and microbial
fermentation. From the rumen, food can be regurgitated to the mouth and chewed again.
This process is called rumination – also known as chewing the cud. The food is then
swallowed again and passes to the second compartment, the reticulum. From the reticulum,
food moves on to the third and fourth chambers, the omasum and abomasum, and on down
the digestive tract. Some cellulose is also broken down in the cecum, but most is fermented
in the rumen.
Camelids
The camelids (camels, llamas, guanacos, vicunas, and alpacas) have 3-chambered
stomachs. They are able to ruminate. Like ruminants, microbes in the stomach of camelids
are able to break down cellulose and convert it to usable products. Llamas – sacules (For
more information see Fowler pg. 970-971.)
Shaded areas indicate
where microbial
fermentation of
cellulose occurs. Most
occurs in the rumen.
(Diagram adapted form
Macdonald – The
Encyclopedia of Mammals
pg. 471) 3
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Teeth
Ruminants and camelids do not have teeth at the front of their top jaw. Instead they

3. have a hardened pad area. They do have incisors at the front of their bottom jaw. Noteincisors
may be present on the top jaw as fighting teeth (i.e. – llamas – I 3 & C1 are fighting
teeth). Pigs and peccaries have large canines, sometimes referred to as tusks.
• Dental formula (permanent) in camels: I 1/3, c 1/1 pm 3/2, m 3/3 x 2 = 34 (Nowak 1351,
Fowler 971)
• Dental formula in the domestic cow: I 0/3, 0/1, 3/3, 3/3
Feet
The artiodactylids have two or four weight-bearing toes on each foot. “The weightbearing axis
of the limb passing between the third and fourth digits. All modern artiodactyls
have lost the first digit.” (Macdonald 468)
Horns & Antlers
Many ruminant artiodactylids have horns or antlers. Good color picture of horns & antlers on
pg. 274 of The Way Nature Works.
Horns
• Horns have 2 parts:
1) a bone knob, over which a
2) horn sheath lies.
The sheath is comprised mainly of keratin.
• Generally speaking, horns are not shed.
They are permanent features and grow as
the animal ages. The exception to this rule
is found in the Pronghorn. Pronghorn shed
their horn sheaths yearly after the rut.
Giraffe “horns” are technically not horns. They are called ossicones (AH-suh-cones). The
ossicones are made of bone and are covered with skin and hair.
Rhino horn differs slightly from other horns. There is no bony core in rhino horn (Fowler 489).
There is a short bony bump on the skull that helps anchor the horn to the head.
Antlers
• Antlers are composed of bone. As they grow they are covered with “velvet” – a special
skin-like layer that provides a blood supply and nutrients to the growing antlers.
• Antlers are usually branched.
• Antlers are shed yearly.
Scent glands – Many bovids (antelope, sheep, goats, etc.) and many cervids (deer) have special
scent glands on their bodies used to mark their territories. The glands may be found in the
following locations: inter-digital (btw. the hooves), carpal (shin), preorbital, around the base of
the horns/antlers, subauricular, dorsal, inguinal, metatarsal, and preputial. (Estes 7) 4
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Order – PERISSODACTYLA

4. (Odd-toed ungulates – horses, rhinos, tapirs)
Feet
Members of the perissodactylid order have one or three toes that bear the animal’s weight
as it moves. “The axis of the limb passing through the middle (or single) *toe+. All modern
species have lost the first and fifth digits in the hind foot, and the first digit in the forefoot.”
(Macdonald 468)
Digestive system
Horses, rhinos, and tapirs do not ruminate. Food (except for cellulose in plants) is broken
down in the stomach and moves down the digestive tract to the cecum (“SEE-come”) and colon
(large intestine). In the cecum and colon, cellulose is broken down by microbes and undergoes
fermentation to become products that the body can absorb and use. Thus, horses, rhinos, and
tapirs are sometimes referred to as hindgut fermenters, because the fermentation process
occurs
farther down the digestive
tract, in the “hindgut”
(cecum and colon).
In the hindgut
fermenters, “the digestion
of cellulose is less
efficient, as the food is
only retained for about
half the length of time.”
(Mcdonald 471).
It takes less time
for food to pass through
the digestive tract of
hindgut fermenters than
to pass through that of
ruminants.
Shaded areas indicate where microbial fermentation of cellulose occurs.
(Diagram adapted from Macdonald – The Encyclopedia of Mammals pg. 471)
Teeth
Incisors
• Horses have incisors at the front of their mouth on both the top and bottom jaws. Dental
formula of domestic horse: I 3/3, C 1/1, P 3-4/4, M 3/3 (Dyce, Sack, &Wensing 473)
• White rhinos and black rhinos do not have incisors. Indian rhinos have two tusk-like
incisors on the bottom jaw. Dental formula in African rhinos: I 0-1/0-1, C 0/0-1, P 3-4/3-
4, M 3/3 (Fowler 935) Good pictures of crowns in Grzimek’s Vol. 4 pg. 610 (Grzimek

5. 610)
Canines Most rhinos either lack canine teeth or have poorly developed/modified canines on the
bottom jaw.
Premolars & Molars – For a description of the cheek teeth see information under “General
Characteristics of Ungulates”