Giraffes (Giraffa spp.) Fact Sheet: Diet & Feeding

• Browsers: eat leaves and young shoots.
  • Acacia and Combretum spp. predominant in their diet; also, Terminalia and Ziziphus spp. (Wilson and Mittermeier 2011)
  • Eat seeds, pods, acacia bark, flowers when available (Brenneman et al. 2009; Dagg 2014).
  • Rarely eat grass.
  • Will chew on bones ("osteophagia"), presumably for minerals such as calcium and phosphorus (Wilson and Mittermeier 2011; Seeber et al. 2012 Table S1).
    • Have high calcium requirements due to large, fast-growing skeleton.
    • More commonly observed in captive than free-ranging individuals. 
• Diet includes more than 100 plants (Bercovich and Berry 2014), but bulk of diet usually made up of only a few species of trees and woody bushes (Parker and Bernard 2005).
• Acacia spp. are favored in all locations.
  • High protein, water, and calcium content (Rubanza et al. 2007; Wilson and Mittermeier 2011)
  • New and growing shoots preferred, when available (Parker and Bernard 2005)
• Additional species consumed differ depending on location and season.
  • Include the genuses Rhus, Euclea, Schotia, Boscia, Canthium, Combretum, Commiphora, Terminalia, Harrisonia, Pappea, Pterocarpus, Cassia, Lycium, Lonchocarpus, Grewia (e.g., Parker and Bernard 2005, O'Connor et al. 2015).
  • Rainy season: Mostly deciduous species.
  • Dry season: Mostly evergreen species.
• Smaller herd size during dry season may reduce intra-group competition for limited food resources (Bercovitch and Berry 2009a).
• Consume 34-75 kg (75-165 lbs) of browse per day.

Foraging

• Able to feed at heights unreachable by all other browsers, except for the elephant (Wilson and Mittermeier 2011; Dagg 2014).
  • Pruned browse line along the undersides of trees at a height of about 4.3-5.5 m (14-18 feet).
  • Likely affects the shape of trees, like Acacia.
  • Long, prehensile, sticky tongue enables a giraffe to feed on hard-to-reach leaves.
  • Elongated occipital condyles (where the skull attaches to the neck) enable a giraffe to extend its head to a completely vertical angle, increasing its reach while browsing.
• Because males are so much taller than females, they browse in a higher region of a tree, potentially reducing competition for food (O'Connor et al. 2015); also see Mramba et al. (2017).
• Mouth protected against thorns (Wilson and Mittermeier 2011)
  • Strip leaves between lower teeth and hardened upper dental pad.
  • Tongue has small, thickened papillae

Acacia defense response to giraffe browsing (Bernard and Parker 2005; Brenneman et al. 2009)

• Increase thorn length and numbers
• Increase tannin production within leaves, especially in the canopy, where giraffes prefer to browse.
  • New acacia shoots generally high in protein but low in tannins.
  • Giraffe induce shoot growth in some Acacia species through their browsing.
• Airborne release of tannins; giraffes may move upwind.
• Drought and intense browsing by many giraffe may limit the re-growth ability of acacia.

Digestion (Dagg 2014, except as noted)

• Very little chewing when food first eaten.
• Quickly swallowed, partially digested, and later regurgitated.
• Chew more thoroughly at a later time ("chewing cud"), like other ruminants.
• Can chew cud at any time of the day.
• Four-chambered stomach highly efficient.
• Surface covered in long papillae.
• Vastly increases surface area for nutrient absorption.
• Largest surface area of any ruminant.
• Genetic adaptations for digesting acacia (Agaba et al. 2016)
• Digest acacia's fatty acids
• Cope with toxic alkaloids

Water (Dagg 2014, except as noted)

• Wet season: obtain most or all water from consuming leaves and dew.
• Dry season: drink at least every three days, up to 38 liters (10 gallons) at a time.
• Must spread forelegs wide or kneel to reach water while drinking.
• In some arid habitats, may get all their water from plants (David O'Connor, personal communication)

Image credit: © Patricia van Casteren, patries71 at Flickr. Some rights reserved.

Apfelbach (1990)
Brenneman et al. (2009)
Bercovitch and Berry (2009a)
Bercovich and Berry (2014)
Dagg (2014)
Estes (1991)
Innis (1958)
Kingdon (1997)
MacClintock (1973)
O'Connor et al. (2015)
Parker and Bernard (2005)
Pellew (1984)
Rubanza et al. (2007)
Spinage (1968)