Giraffes (Giraffa spp.) Fact Sheet: Physical Characteristics

(Kingdon 1997, tail length; Ciofolo and Le Pendu 2013, all other measurements)

*Notes on measurements:

Tail length: range values. All other measurements cited as mean value (± 1 standard deviation). Sample size is 15-18 individuals for all Ciofolo and Le Pendu (2013) data.

*Total length: Measured from tip of snout to posterior end of tail. Equivalent to the head and body length and tail length added together.

Characteristics (Wilson and Mittermeier 2011, except as noted)

• Tallest mammal
• Very long neck
• Short, stiff mane
• Long, black hair on tail; used as an insect-swatter (Dagg 2014)
• Shoulders high, sloping down to hind quarters. Legs of approximately equal size. Apparent slope caused by tall dorsal spines on the thoracic vertebrae.
• No upper incisors or canines
• Long prehensile tongue: 50 cm (20 in)
• Large brown eyes bordered by long, black lashes
• Large hooved feet

Ossicone "horns" (Wilson and Mittermeier 2011)

• Specific to Giraffids
  • Horn-like growths
  • Permanent and unbranched
  • Different than true horns (kertain and other proteins covering bone), but often called "horns" in literature
    • Found in other animals, like cattle, buffalo, antelope, and rhinocerous
• Bony in adults; soft and cartilagenous in calves
  • Ossification proceeds from the skill, eventually fusing with the skull
• Covered by skin and hair (except the tips, which are hairless, especially in males)
• Up to 13.5 cm (5.3 in) long
• See Sexual Dimorphism, below, for differences between adult male and female horns.
• Ossicones present at birth.
  • Formed of small bumps of cartilage, unattached to skull.
  • Covered with skin and tufts of hair.

Pelage

• Background is medium-to-reddish brown. Broken into splotches by buff-colored borders.
• Pattern does not change.
• Blotches of some individuals (particularly males) may darken with age (Berry and Bercovitch 2012).
  • Likely not characteristic of all giraffe
  • In males, turn from brownish to coal-black between about 7-10 years of age.
  • Evolutionary significance of this darkening unknown.
• Individuals can be recognized by their unique markings.
• Rarely, individuals without spots are born all dark (almost black), tan (spots barely visible), or white (although no true albinos have been observed)
• Reticulated giraffe, Kordofan giraffe, and Nubian giraffe have distinctive coat markings (Fennessy et al. 2016)

Size

• Adult males substantially taller and heavier than females

Horns (ossicones) (Wilson and Mittermeier 2011)

• Females: two ossicones
  • Generally thinner than in males
  • Ends are tufted with hair
• Males: commonly, two ossicones
  • Ends hairless, often callused
  • May also have a medial ossicone
    • Center of forehead
    • Secondary sexual male characteristic
    • Absent in females, though a ridge may be present
  • Sometimes, additional ossicones behind the primary pair
• Also see horn development.

Skull

• Skulls of mature males typically weigh 2-3 times that of females; extensive ossification over front of skull, above the eyes, and on the rostrum.
• Females may have additional bony knobs on forehead; not as extensive as in males.

Neck

• Possess 7 cervical vertebrae, the same as other mammals (Wilson and Mittermeier 2011).
• Each of these vertebra is greatly elongated, producing the longest mammalian neck (Wilson and Mittermeier 2011).
• Neck ligaments enlarged and strengthened to support heavy neck and head (Agaba et al. 2016).

Color vision

• Can distinguish between red, orange, yellow-green, green, blue, and violet.

Skin

• Color: dark gray (Wilson and Mittermeier 2011)
• Thicker skin on flanks and rump may protect against lion claw wounds (Sather et al. 2010; Strauss and Packer 2012).
• Sweat glands present, but do not seem to functional; may be remnants of the the giraffe's evolutionary ancestors (Dagg 2014).
  • Patches radiate heat. May help in very hot weather.

Circulatory System

• Giraffe's cardiovascular system thought to have co-evolved with its unique skeletal traits (Agaba et al. 2016).

• Specializations regulate blood flow to the giraffe's head (Wilson and Mittermeier 2011; Dagg 2014).
  • Giraffes are up to 18 feet tall, and one would expect blood to rush to the brain when a giraffe lowers its head to drink, or to drain away from the brain when the head is lifted back up.
  • Either scenario could result in fainting.

• High blood pressure helps maintain sufficient blood flow to the brain.
  • Systemic (arterial) blood pressure at birth is comparable to other mammals, but it rises as a giraffe grows and its neck elongates (Mitchell and Skinner 2009).
  • Average systemic blood pressure is 203 mm Hg, dropping to 100 mm Hg at the head (Mitchell and Skinner 2009; calculated average of 29 reports).
  • Systemic blood pressure at the heart with the neck held 55° to the vertical is calculated to be 208 mm Hg—nearly twice the predicted value for other species of similar mass (Mitchell and Skinner 2009).
  • Genes, controlling cell shape and heart muscle contraction, help regulate blood pressure (Agaba et al. 2016)

• Heart structure: quite different from other mammals
  • An early study (Goetz 1955) reported a very large (11.25 kg) heart for giraffes, but this may have been an error in measurement.
  • A comprehensive study of the giraffe cardiovascular system (Mitchell and Skinner 2009) showed heart size relative to body mass to be comparable to that of other mammals.
  • Heart structure is quite different from that of other mammals (Mitchell and Skinner 2009)
    • As a giraffe grows, the left ventricular and interventricular walls become much thicker than in other mammals, enabling the heart to contract much more strongly.
    • A giraffe heart can generate an output of 6,000 mm Hg per second, 2.5 times that of a cow heart and 5 times that of a human heart (Patterson et al. 1965).

• Valves and large veins play a role when the head is lowered
  • Numerous one-way valves in the jugular vein and its offshoots prevent blood from flowing back to the brain.
  • The jugular vein, which is large (2.5 cm, 1 inch, in diameter) and elastic, stretches to increase its capacity and act as a blood reservoir, counteracting the force of gravity on the blood.

• Muscle fibers play a role when the head is raised
  • Muscle fibers surround veins that lead to the heart.
  • These contract when the head is raised, slowing the flow of blood.

Coping with the African heat (Dagg 2014)

• Unusual body shape provides a large surface area. Easier to dissipate heat than retain it (a disadvantage in cooler weather).
• Raise body temperature during the day, up to 40°C, to reduce water loss.
• Brain is cooled as the giraffe breathes through its nose.

Close up of young giraffe.

Image credit: © San Diego Zoo Wildlife Alliance. All rights reserved.

Berry and Bercovitch (2012)
Dagg (2014)
Goetz (1995)
Mitchell and Skinner (2009)
Patterson et al. (1965)
Sather et al. (2010)
Wilson and Mittermeier (2011)