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

Western Gray Kangaroo (Macropus fuliginosus)

Physical Characteristics

Body measurements

Attribute Males Females
Body weight 18-72 kg (39-158 lb) 17-39 kg (37-86 lb)
Head-to-tail length* 94.6-222.5 cm (37.2-87.6 in) 67.1-174.6 cm (26.4-68.7 in)
Tail length 42.5-100 cm (16.7-39.4 in) 44.3-81.5 cm (17.4-32.1 in)

 

Data source: Eldridge and Coulson (2015)

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

General Appearance

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)

Sexual Dimorphism

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

Identification

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

Other Physical and Physiological Characteristics

Teeth (Dawson 2013)

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

Thermal Benefits

Western Gray Kangaroo - San Diego Zoo Safari Park

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.

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