Perception Channels: tactile ; chemical
Other Physical Features: endothermic ; bilateral symmetry
Key Reproductive Features: gonochoric/gonochoristic/dioecious (sexes separate); sexual
Diversity of Living Giraffidae (Giraffe and Okapi)
The family Giraffidae is one of a number of families in the mammal order Artiodactyla (even-toed ungulates). There are just two living species, the Giraffe (Giraffa camelopardalis) and the Okapi (Okapia johnstoni). Giraffes occur in a patchy distribution in savannas across parts of sub-Saharan Africa. Okapi are endemic to the forests of DR Congo.
Giraffes are the tallest mammals in the world. At birth, they stand between 1.5 and 1.8 m; at maturity, females may reach 4.5 to 5 m and males 5 to 6 m. Body mass at birth is around 100 kg (less in captive animals). Body mass of mature females can reach 1100 kg and mature males can reach 1500 kg. Giraffes have very long necks although, like nearly all other mammals, they have just seven cervical vertebrae—their cervical vertebrae are very long (as are their lower leg bones). The neck is held upright when a Giraffe walks, but stretched forward when it is running or moving uphill. A variety of morphological and physiological adaptations related to blood flow prevent problems from arising when the Giraffe lowers and raises its neck (e.g., to drink).
Okapi are secretive forest-dwellers that have been known to science only since 1901 (although they were already familiar to local indigenous people). They share some evident similarities with Giraffes, but bear an overall resemblance to some of the larger antelope species. In contrast to Giraffes, Okapi females are taller and more massive than males.
Ecology and Behavior
The structure of a Giraffe herd is fluid and the same individuals rarely stay together for long. Females and young are usually found in a herd together; younger males may form bachelor herds. Mature bulls are generally solitary, although they may join a temporary harem of females. Unlike Giraffes, which are not territorial, Okapi of both sexes hold territories.
The Giraffe is one of just two ungulate species known to have a gestation period longer than a year (450 days). In the wild, females become mature at 4 to 5 years. When her young is born (usually just one), a female may produce 10 liters of milk each day. Giraffe milk is richer in fat and protein than that of dairy cows. The gestation period for Okapi is shorter than that of Giraffes, around 14 months.
Giraffes are almost exclusively browsers. Acacia leaves are a major component of Giraffe diets, as are Combretum trees. Giraffes favor food plants rich in calcium and phosphorus, which are important in building their large skeletons. Giraffes use their powerful prehensile tongues to pull shoots and twigs into their mouths, where leaves are stripped off between the lower teeth and the upper dental pad. The tongue is very rough and Giraffes are reported to munch fully hardened thorns, although they prefer to feed on vegetation without thorns. Okapi feed on plants in their forest habitat. They use their prehensile tongues to strip leaves from branches and bring them into the mouth. An Okapi's tongue is so long it can wash its eyelids and ears with it.
Although Giraffes are generally able to survive on the water content of their food, when water is accessible they tend to come to drink at intervals of three days or less. Drinking Giraffes, with head lowered and forelegs splayed, are particularly vulnerable to predators.
Within historical times, Giraffes were widely distributed throughout Africa, but never in the tropical rainforest of the Congo River, which is home to the Okapi. The Giraffe's current distribution is far smaller than it once was and very patchy, but Giraffes can be found in a range of dry savanna habitats, from scrub to woodland, and are closely associated with acacia thornveld, as well as deciduous woodland tree species.
Male Giraffes often fight, striking one another with their necks and heads. These bouts are generally highly ritualized in young males, causing no injury, but when they occur between mature bulls they tend to be more serious. Although it has been suggested that the long necks of Giraffes are a product of sexual selection in males, with longer and heavier necks being favored in the struggle among males for mating opportunities, necks of both sexes grow in length and mass at similar rates.
Communication among Giraffes seems to involve mainly vision and olfaction.
Conservation Status of Giraffes and Okapi
Although the Giraffe is listed on the IUCN Red List as Least Concern, it has declined dramatically over parts of its range, especially in West Africa. It is now extinct in many countries where it once occurred, including Burkina Faso, Eritrea, Guinea, Malawi, Mauritania, and Senegal (and possibly Mali and Nigeria). Some named subspecies are in trouble as well. The Okapi is listed by IUCN as Near Threatened, although given its secretive nature, an accurate population assessment is difficult. Habitat loss is a serious threat. Okapi were once presentin Uganda (and possibly elsewhere) but are no longer believed to occur anywhere outside DR Congo.
The Giraffidae are a family of ruminant artiodactyl mammals that share a common ancestor with deer and bovids. This family, once a diverse group spread throughout Eurasia and Africa, presently comprises only two extant genera, the giraffe (one or more species of Giraffa, depending on taxonomic interpretation) and the okapi (the only known species of Okapia). Both are confined to sub-Saharan Africa: the giraffe to the open savannas, and the okapi to the dense rainforest of the Congo. The two genera look very different on first sight, but share a number of common features, including a long, dark-coloured tongue, lobed canine teeth, and horns covered in skin, called ossicones.
The giraffids are ruminants of the clade Pecora. Other extant pecorans are the families Antilocapridae (pronghorns), Cervidae (deer), Moschidae (musk deer), and Bovidae (cattle, goats and sheep, wildebeests and allies, and antelopes). The exact interrelationships among the pecorans have been debated, mainly focusing on the placement of Giraffidae, but a recent large-scale ruminant genome sequencing study suggests Antilocapridae are the sister taxon to Giraffidae, as shown in the cladogram below.[1]
Ruminantia Tragulina PecoraGiraffidae 
The ancestors of pronghorn diverged from the giraffids in the Early Miocene.[1] This was in part of a relatively late mammal diversification following a climate change that transformed subtropical woodlands into open savannah grasslands.
The fossil record of giraffids and their stem-relatives is quite intensive, with fossil of these taxa include Gelocidae, Palaeomerycidae, Prolibytheridae, and Climacoceratidae.[2][3] It is thought the palaeomerycids is the ancestral group that given rise to the prolibytherids, climacoceratids and the giraffids, all three forming a clade of pecorans known as Giraffomorpha.[2][4] The relationship between the climacoceratids and giraffids is supported by the presence of a bilobed canine,[2] and have been postulated into two hypotheses. One is the climacoceratids were the ancestors of the sivatheres, as both groups were large, deer-like giraffoids with branching antler-like ossicones, while an extinct basal group of giraffoids, canthumerycines, evolved into the ancestors of Giraffidae.[3] Another more commonly supported hypothesis is climacoceratids were merely the sister clade to giraffids, with sivatheres being either basal giraffids[2] or descended from a lineage that also includes the okapi.[5] While the current range of giraffids today is in Africa, the fossil record of the group has shown this family was once widespread throughout of Eurasia.[2][3][5]
Below is the phylogenetic relationships of giraffomorphs after Solounias (2007),[2] Sánchez et al. (2015)[4] and Ríos et al. (2017):[5]
Giraffomorpha Giraffoidea Giraffidae
Below is the total taxonomy of valid extant and fossil taxa (as well as junior synonyms which are listed in the brackets).
Family Giraffidae J.E.Gray, 1821
The giraffe stands 5–6 m (16–20 ft) tall, with males taller than females. The giraffe and the okapi have characteristic long necks and long legs. Ossicones are present on males and females in the giraffe, but only on males in the okapi.[6]
Giraffids share many common features with other ruminants. They have cloven hooves and cannon bones, much like bovids, and a complex, four-chambered stomach. They have no upper incisors or upper canines, replacing them with a tough, horny pad. An especially long diastema is seen between the front and cheek teeth. The latter are selenodont, adapted for grinding up tough plant matter.[7] Like most other ruminants, the dental formula for giraffids is 0.0.3.33.1.3.3. Giraffids have prehensile tongues (specially adapted for grasping).[8]
The extant giraffids, the forest-dwelling okapi and the savannah-living giraffe, have several features in common, including a pair of skin-covered horns, called ossicones, up to 15 cm (5.9 in) long (absent in female okapis); a long, black, prehensile tongue; lobed canine teeth; patterned coats acting as camouflage; and a back sloping towards the rear. The okapi's neck is long compared to most ruminants, but not nearly so long as the giraffe's. Male giraffes are the tallest of all mammals: their horns reach 5.5 m (18 ft) above the ground and their shoulder 3.3 m (11 ft), whereas the okapi has a shoulder height of 1.7 m (5 ft 7 in).[9]
The two extant genera are now confined to sub-Saharan Africa. The okapi is restricted to a small range in the northern rainforest of the Democratic Republic of Congo. Although the range of the giraffe is considerably larger, it once covered an area twice the present size — all parts of Africa that could offer an arid and dry landscape furnished with trees.[9]
The social structure and behavior is markedly different in okapis and giraffes, but although little is known of the okapi's behavior in the wild, a few things are known to be present in both species:[9]
Giraffes are sociable, whereas okapis live mainly solitary lives. Giraffes temporarily form herds of up to 20 individuals; these herds can be mixed or uniform groups of males and females, young and adults. Okapis are normally seen in mother-offspring pairs, although they occasionally gather around a prime food source. Giraffe are not territorial, but have ranges that can dramatically vary between — 5 and 654 km2 (1.9 and 252.5 sq mi) — depending on food availability, whereas okapis have individual ranges about 2.5–5 km2 (0.97–1.93 sq mi) in size.
The Giraffidae are a family of ruminant artiodactyl mammals that share a common ancestor with deer and bovids. This family, once a diverse group spread throughout Eurasia and Africa, presently comprises only two extant genera, the giraffe (one or more species of Giraffa, depending on taxonomic interpretation) and the okapi (the only known species of Okapia). Both are confined to sub-Saharan Africa: the giraffe to the open savannas, and the okapi to the dense rainforest of the Congo. The two genera look very different on first sight, but share a number of common features, including a long, dark-coloured tongue, lobed canine teeth, and horns covered in skin, called ossicones.
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