Koala (Phascolarctos cinereus) Fact Sheet: Diet & Feeding

Obligate browsing folivore, feeding almost exclusively on leaves of Eucalyptus (Hume 1999)

• These leaves represent a low energy resource with extensive plant defenses (tannins, oils, lignin)
  • Some defenses such as lignins and some tannins interfere with digestive process
  • Other defenses such as additional tannins and oils are toxic to animal trissue
• Occasionally forage in non-Eucalyptus species: Melaleuca, Pinus, and others
  • Only a very small percentage of total diet

Prefer leaves of only selected species of Eucalyptus tree, preferences vary between populations, seasons, individuals

• Nearly 900 species of Eucalyptus in Australia (Brooker et al. 2006)
• Approximately 70 species reported eaten by koalas  (Jackson et al. 2003)
  • Southern Australia preference: E. viminalis, E. ovata, and E. globulus
  • Northern Australia preference: E camaldulensis, E. tereticornis, E. microcorys, and E. punctata
  • Koalas at San Diego Zoo (originally from Queensland) prefer E. camaldulensis; would rather not eat E. viminalis (Higgins et al. 2011)

• Seasonal changes in species preference possibly due to (Jackson 2007) (Moore & Foley 2005):
  • Water content
  • Increased concentration of toxic chemicals (especially FPCs or formylated phloroglucinol compounds)
• Other important factors in eucalypt selection:
  • Tree size (larger tree offers more browsing possibilities)
  • Nitrogen levels (higher is better)
• Eat about 600-800g of leaves/day
  • May also include soft stems, flowers, and occasionally bark
  • Lactating females increase intake 20-25%

Preferred eucalypt trees usually grow in areas with higher-quality soils (Jackson 2007)

• These same regions are desired as prime agricultural land

Digestion (Hume 1999)

• Koalas are an example of a mammal well adapted for overcoming plant defenses of Eucalyptus leaves
  • Stomach has cardiogastric gland, which increases acid and enzyme production; wombats have a similar gland
• Stomach is small in relation to the digestive tract
• Large food particles pass through the colon and are excreted rapidly 
• Small particles undergo microbial fermentation in the caecum (largest of any mammal in proportion to body size)
• Produce dry faecal pellets (water conservation for an animal that rarely drinks in the wild or in zoo settings)

Feed and move around about 4 hours/day

• Most movement between 5pm-12am
• Feed intermittently for approximately 20 minutes at a time

Foraging behavior

• Pulls a branch to its nose with forepaw before eating
• Smell plays a role in identifying preferred species
• Usually select a single leaf at a time
• Sharply ridged molars slice up leaf into small pieces 
• When molars wear down with age, starvation a common problem (Jackson 2007)
  • May consume up to 41% more leaves and chew much longer than younger koalas with sharper teeth

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

Brooker et al. (2006)
Cork & Sanson (1990)
Grand & Barboza (2001)
Higgins et al (2011)
Hume (1999)
Jackson (2003, 2007)
Martin & Handasyde (1999)
Moore & Foley (2000, 2005)
Ullrey et al. (1981a,b)