Western Gray Kangaroo (Macropus fuliginosus) Fact Sheet: Physical Characteristics

Body measurements

Data source: Eldridge and Coulson (2015)

*Note: An early source of these head-to-tail length data is Strahan (1983).

Head and body

• Large body (Eldridge and Coulson 2015)
• Brownish gray in color (Eldridge and Coulson 2015)
• Long ears (Eldridge and Coulson 2015)
• Furred at the base, then bare to the tip (Staker 2006)
• Differences for Kangaroo Island population (Eldridge and Coulson 2015)
• Shorter limbs, tail, and ears
• Coloration is sooty brown

Limbs: paws, legs, feet, and tail

• Paws have longer digits and nails than red kangaroos (Staker 2006)
• Second and third toes of macropods are fused together (Staker 2006)
• Tail is thick and muscular (Dawson et al. 2014); used for balance and stabilizing (Staker 2006)

Regional differences in appearance (Dawson 2013)

• Appearance gradually changes across southern Australia
• In Western Australia, more brownish and more slender-bodied
• In South Australia, Victoria, and New South Wales, stockier with more dark brown on the head and back; more bluish gray underneath
• On Kangaroo Island (M. f. fuliginosus)
• Shorter limbs, ears, and tail than mainland forms

Pelage

• Dusty to chocolate brown, or brownish gray along their back (Eldridge and Coulson 2015)
• More pale and gray on underside and often on limbs (Eldridge and Coulson 2015)
• White stripe along lower jawline (Staker 2006)
• Face, paws/feet, and end of the tail almost black; elbows often dark (Eldridge and Coulson 2015)
• Ears dark with sparse hair; more pale inside, with contrasting white fringe (Eldridge and Coulson 2015)

Distinct sexual dimorphism

• Males larger than females (Garnick et al. 2016)
• Males have more muscle mass in their forearms and chest (Warburton et al. 2013)
  • Used in clasping, holding, and pulling opponents in male-male competition; also visual signaling to rivals
• Males have a strong, curry-like odor (Eldridge and Coulson 2015)
  • Distinct; not observed in other kangaroo species

Similar in appearance to eastern gray kangaroo

• Adult description (Dawson 2013, except as noted)
  • Eastern gray kangaroo has more gray-brown on its body, a pale gray face, and dark shading around the eyes
    • Subtle difference in ear shape, as well (S. Garnick, personal communication, 2017)
  • Eastern gray kangaroo has fine hair over its entire ear, whereas western gray kangaroo only has fur at the base of its ear (Staker 2006)
  • Western gray kangaroo is more brownish, usually has a dark brown face, and has a black patch around its elbow
  • In western Australia, adult western gray kangaroos more commonly have white and black blotches on their face compared to eastern gray kangaroos (S. Garnick, personal communication, 2017)
  • The two species are easily confused at night; can use ear shape to distinguish (S. Garnick, personal communication, 2017)
• Joey description (Staker 2006)
  • Unfurred western gray kangaroo joeys look the same as eastern gray kangaroo joeys
  • When furred, have a distinctive white stripe of fur along their lower jaw line, no fur on their ears, and darker fur
  • Lighter chest coloration is more pronounced than in eastern gray kangaroos
  • Some joeys have blotches of black or white on their faces or foreheads; not seen in eastern gray kangaroo joeys

Teeth (Dawson 2013)

• Specialized for grazing (grinding and cutting through tough grass)
• Over time, worn down molars are shed and replaced (molar progression)
• Two sides of lower jaw are not fused together; increases the surface area for biting and chewing, and improves feeding efficiency
• Also see Feeding

Adaptations for hopping at high speed (Dawson 2013, except as noted)

• High concentrations of mitochondria (intracellular structures that produce energy for activity) around the upper hind leg and pelvis
• High densities of blood capillaries in the muscles
• Large heart
• High lung capacity
• Large Achilles tendon in the lower hind leg (elastic; conserves energy)
• Muscular tail acts as a counterbalance during high speed hopping (see discussion by Dawson et al. 2014)

Thermoregulation (Dawson 2013)

• Body temperature near 36°C (96.8°F), slightly lower that of than placental mammals
• Body temperature finely controlled, despite fluctuating ambient temperature conditions
• Avoid sun during hot weather and seek the sun during cold weather
• Avoid windy conditions during cold weather because it disrupts the insulation their fur provides (eastern gray kangaroo; likely western gray kangaroo, also)
• Prevention of overheating
  • Lie quietly in the shade; dig hip holes
  • Adopt body positions that expose only a small surface area to the sun (red kangaroo)
  • Blood flow increases to parts of the body with less fur to allow heat to radiate away
  • Heat is dissipated from the body by panting, sweating, and licking; helps regulate body temperature, but water is lost from the body (red kangaroo)
    • If a kangaroo must hop rapidly during hot conditions, sweating stops as soon as exercises stops to conserve water
      • Hopping is avoided as much as possible in hot conditions; a kangaroo’s body produces 25x more heat while hopping than while resting
    • During licking, saliva drips from the mouth and nose to a small area of the forearm where dense networks of fine blood vessels carry heat away when wet, resulting in significant heat loss
      • Once considered a ‘primitive’ adaptation; now understood as an optimizing strategy—“water maximally used for thermoregulation”
  • Benefits of fur
    • Provides protection from the sun’s heat
      • Reflects about 30% of the incoming radiation and holds the rest of the heat close to the fur’s surface, where it can be dissipated by the wind
    • Provides insulation against heat loss, especially when feeding at night
    • Thickness of fur may change seasonally to balance the need to stay warm with the need to dissipate heat through water evaporation
• Responses to cold
  • Reduced blood flow to legs and tail, where much heat is lost
  • Shivering to generate additional warmth
  • Growth of thicker fur during winter

Digestion and metabolism (Dawson 2013)

• Forestomach used in fermentative digestion
  • Other herbivorous mammals, such as horses and rabbits, use hindgut fermentative digestion
  • Also see Feeding
• Kangaroos have a relatively low basal metabolic rate; this is true of marsupials compared to placental mammals

A coat of insulating fur keeps a kangaroo cooler during the day and warmer at night.

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

Image notes: Western gray kangaroo at the San Diego Zoo Safari Park.