Western Gray Kangaroo (Macropus fuliginosus) Fact Sheet: Diet & Feeding

Food

• Mainly grasses; native and exotic pasture grasses strongly preferred (Eldridge and Coulson 2015)
  • Western gray kangaroos select newly germinated grasses after rain (Eldridge and Coulson 2015)
• Some shrubs and trees (Casuarina spp., Casuarinaceae) preferred during dry conditions (Eldridge and Coulson 2015)
  • Eat more browse than eastern gray kangaroo (Staker 2006)
• Grass trees, lilies, forbs, chenopods, succulents, shrubs, and heath also consumed (Eldridge and Coulson 2015)
• In Western Australia, also consume lupin crops and “poison bush” (Gastrolobium spp., Fabaceae) (Eldridge and Coulson 2015)
• Western gray kangaroo has a high tolerance to the plant toxin fluoroacetate, which is found in many legumes endemic to southern parts of Western Australia (Staker 2006; Dawson 2013)
• In some locations, microhabitats of western gray, eastern gray, and red kangaroos do not overlap; in other locations, they feed in the same area on the same plants (Dawson 2013)
• Gray kangaroos eat more grasses than the red kangaroo (Munn et al. 2014)
• Macropods eat little protein in the wild (Staker 2006), but opportunistically eat meat, on occasion (Sarah Garnick, personal communication, 2017)

Water

• A 25 kg (55 lb) western gray kangaroo’s body is 74% water; they drink about every two days (Dawson 2013)
  • May also ingest dew moisture that condenses on plants at night (Priddel 1986)
• Munn et al. (2014) found little difference in water use between western gray and red kangaroos
• Kidneys of the western gray kangaroo may not be quite as efficient as the eastern gray kangaroo, euro, and red kangaroo, but are still highly efficient compared to domestic livestock animals (e.g., goats, sheep) (Dawson 2013)
  • As ruminants, sheep feed throughout the day, requiring more water (Munn et al. 2014)
• When feeding on fresh grass (during cooler times of the year), red kangaroos can maintain water balance without drinking (Dawson 2013)
• Red kangaroos can withstand large water losses (above 20% of their body weight) and replace half of that water within 5 minutes (Dawson 2013)
  • Humans experience severe debilitation and circulatory collapse when 12% of our body weight is lost

Kangaroos are adapted to a grazing lifestyle in grasslands (Dawson 2013, except as noted)

• Often compared to grazing ungulate ruminants (e.g., cattle, sheep, antelope, and deer) of other continents
• Kangaroos do not regurgitate and re-chew their food like ruminant grazers (e.g., cattle, sheep)
• Kangaroos adjust feeding strategies to counter plant defenses and gain better nutrition
• Western gray kangaroos exhibit behaviors similar to kangaroos in extremely arid regions of Australia (e.g., red kangaroo) (Munn et al. 2014)
• Large, adult males seem to consume a higher proportion of grass than adult females do (Eldridge and Coulson 2015)

Structures for eating and digesting grass (Dawson 2013, and as noted)

• Specialized foregut digestion
  • Microbes ferment and break down fibrous grasses before the food passes to the acid-secreting gastric stomach and small intestine
    • Microorganisms make energy available and produce vitamins, essential nutrients, and microbial proteins
      • Microorganisms obtain about 30% of the energy available; kangaroos, the other 70%
      • Kangaroos need less protein than grazing placental mammals of the same size
    • Larger kangaroos can maintain a larger fermenting foregut, allowing them to retain fibrous food longer
  • Microorganisms also reduce the potency of toxic substances plants use in defense against herbivores
• Teeth and lower jaw
  • Kangaroos grasp and cut grass with their incisors, often with a jerk of the head
  • Two sides of lower jaw are not fused together; increases the surface area over which a kangaroo can bite and chew—improving feeding efficiency
  • Grass passed back to molars, which shred/chop the grass to speed digestion
    • Molars have lengthwise cutting ridges; wallabies eat softer leaves and do not have these ridges on their molars
  • Kangaroos alternate chewing on left and right sides of their mouth
  • Cutting surfaces of molars wear down due to presence of dust/grit on leaves and silica contained in leaves; only one pair of teeth occlude at a time (reduces wear) (McArthur and Sanson 1988; Sarah Garnick, personal communication, 2017))
    • Teeth move forward and are shed from the jaw; rear molars fall out only in very old individuals (mechanism is not well understood in large kangaroos)

Advantages of sociality while feeding (Sarah Garnick, personal communication, 2017)

• Vigilant while foraging
• Foraging in a group allows more time to feed

Western gray kangaroos show a feeding preference for pasture grasses.

Here, two cocoa-colored individuals forage on Kangaroo Island.

Image credit: DiverDave via Wikimedia Commons; CC Attribution ShareAlike 3.0 Unported license. Public domain.