Macropus giganteus, Shaw, 1790

Russell A. Mittermeier & Don E. Wilson, 2015, Macropodidae, Handbook of the Mammals of the World – Volume 5 Monotremes and Marsupials, Barcelona: Lynx Edicions, pp. 630-735 : 725

47.

Eastern Grey Kangaroo

Macropus giganteus

French: Grand Kangourou / German: Ostliches Graues Riesenkanguru / Spanish: Canguro gris oriental

Other common names: Forester, Great Grey Kangaroo, Scrub Kangaroo, Scrubber

Taxonomy. Macropus giganteus Shaw, 1790 ,

“native of New Holland” (= Kings Plains , Cooktown , Queensland, Australia).

The long-running historical controversy and uncertainty relating to the correct nomenclature for this species was resolved in 1966 by Opinion 760 of the International Commission on Zoological Nomenclature, which validated M. giganteus Shaw, 1790 , as the name for this species. Placed into the subgenus Macropus within Macropus in 1985. Although Tasmanian population often recognized as a separate subspecies, a recent genetic study revealed no major differentiation within the species. Monotypic.

Distribution. E Australia from Cape York Peninsula, NE Queensland, S to far SE South Australia, and NE Tasmania; also on islands of Bribie, Curtis, Fraser, and North Stradbroke (Queensland), as well as islands of Little Snake, Rotamah, and Sunday (Victoria).

Descriptive notes. Head-body 97-2— 230-2 cm (males) and 95.8-185.7 cm (females), tail 43-109 cm (males) and 44.6-84.2 cm (females); weight 19-90 kg (males) and 17-42 kg (females). A large, highly sexually dimorphic gray-brown kangaroo with long ears and finely haired muzzle. Gray-brown dorsally, including head and tail, paler ventrally (sometimes whitish) and often on limbs. Males generally darker than females, sometimes tinged golden or rufous, particularly on ventral surface. Pinkish staining often present on chest and groin of adult males. Face pale, but darkish around eyes. Terminal third of tail and digits dark. Ears dark outside, paler and more gray inside, with whitish fringe. Conforms to Bergmann’s and Allen’s rules, body size increasing and appendage length decreasing with latitude. Diploid chromosome number is 16.

Habitat. Forest, woodland, mallee scrub, shrubland, and heathland in areas of uniform or summer-dominated rainfall. Prefers unburnt areas. Occurs widely in modified habitats such as pasture, crops, and pine plantations. Found also on golf courses and in urban and peri-urban areas in some parts of range; will use overpasses to cross roads. Ideal habitat has mix of patches of cover, which provide shelter from weather and predators, and open grassy areas, which provide food resources. Occurs from sea level to subalpine areas.

Food and Feeding. A grazer. Prefers leaves of low-fiber, high-nitrogen grasses, both native and exotic, but will also eat sheath, stem, and inflorescence of grasses. Grass comprises almost entire diet at some sites, but less than half at others. Consumption of different grass species can change with location, with season, and after fire. Attracted to recently burnt woodland and immature wheat crops. Non-grass monocotyledons (e.g. reeds), forbs, chenopods, shrubs, ferns, trees, and occasionally moss and bark are also consumed. Soil is ingested at well-used licks in some salt-deficient areas, and individuals need to drink almost every day during summer in dry environments.

Breeding. Females reach sexual maturity from 18 months and males from 42 months. Can breed throughout year, but most births occur in late spring and summer, becoming more synchronous and peaking later in summer in south of range. Breeding is reduced and females may become anestrous during prolonged drought. Females produce one young per pregnancy, although twins have occasionally been reported. Larger females biased offspring sex toward males at one site but not at another. The estrous cycle is 26-81 (mean 46) days and gestation 33-45 (mean 36) days. Exhibits facultative embryonic diapause; females do not have a post-partum estrus, but up to 75% may come into estrus as early as 112 days after birth of incumbent pouch young, possibly in response to improved forage conditions. The resulting blastocyst resumes development, and the female returns to estrus, as the incumbent young reaches end of pouch life. Young spends around eleven months in pouch; after permanent pouch emergence, young accompanies the mother as a young-at-foot until after weaning, at c.18 months. Successful reproduction in one season increases interval to next birth and reduces chance of survival of subsequent offspring. There is intense competition among males for access to females. Males establish dominance relationships through repetitive,ritualized bouts of grooming, display, sparring, wrestling, and kicking. They routinely test the estrous state of females by eliciting urination, nosing the stream, and exhibiting flehmen (lip-curl); males form consort relationships with estrous females, guarding them from rival males before and after copulation, which occurs in one or more 20-30minute bout. In captivity, dominant males sired the most young; compared with nons-sires,sires were heavier and larger, had higher testosterone levels, and were less genetically similar to females. However dominant males did not monopolize paternity in two free-ranging populations; on average almost half (46%) of adult males sired at least one offspring per season.

Activity patterns. Crepuscular to nocturnal. Shows a bimodal pattern of activity in some areas, with peaks around sunrise and sunset, and reduced activity around midnight; a single peak occurred around midnight at another site. High temperatures suppress activity at night. Activity in morning gradually shifts from foraging, usually in the open, to resting, usually in cover; the reverse occurs in afternoon. Daylength largely determines the timing ofthis activity shift, but rainfall can delay onset of resting in morning. A solar eclipse was observed to advance the onset of afternoon foraging. In hot weather, rests in shallow hip-holes excavated in patches of shade during day.

Movements, Home range and Social organization. Largely sedentary, although movements of up to 17 km have been detected. Genetic studies indicate that extensive gene flow (up to 230 km) is common for both sexes. Natal dispersal is male-biased and has been reported up to 15 km. Home ranges of both sexes overlap extensively, but are generally larger for males. Adult males can move up to 5 km between centers of activity. Average home-range area generally small in mesic areas where open pasture adjoins wooded cover: 20 ha (95% harmonic mean, females only) at one site, 43 ha (95% minimum convex polygon MCP, females only) at a second, and 43-96 ha (95% MCP, both sexes) at three other sites. Average ranges are considerably larger in temperate pastoral land (613 ha, 100% MCP, both sexes) and even larger in semi-arid woodland (females 777 ha, males 1356 ha, 100 % MCP). Gregarious; forms open-membership groups, which frequently change in size and composition. Group size is positively related to population density; groups are smaller at night than in daytime, and are smallestin forested habitat and largest in open grassland, where individuals in larger groups spend less time in scanning for predators and more time in feeding. Females with young nearing end of pouch life often isolate themselves from conspecifics and forage closer to cover. Large adult males are also often seen alone as they rove across their home ranges, checking the reproductive status of adult females. Large males may associate with other males and segregate from females in non-breeding season (winter). Subtle, non-random associations occur among individual adult females, which are influenced more by their home-range overlap than by kinship. Sets of adult females having mostly overlapping home ranges, together with their dependent young and resident males, comprise a loose social unit known as a “mob”. The location of a mob, and the boundaries between neighboring mobs, may be influenced by topographical features and partial habitat barriers.

Status and Conservation. Classified as Least Concern on The IUCN Red List. The Eastern Grey Kangaroo is widespread and locally common through much of its range. It is well represented in protected areas and is not currently facing any major threats. Some of its habitat has been lost to urbanization and intensive agriculture. In other areas, however, these kangaroos have benefited from clearing of forest/woodland, establishment of improved pasture, and provision of water for livestock, as well as suppression of predators. These changes have enabled Eastern Grey Kangaroos to expand their range and increase in density in some areas. At some sites they are regarded as overabundant and periodic culling is undertaken. They are also commercially harvested in New South Wales and Queensland. The Tasmanian population declined significantly up to the middle of the 20" century as a result of habitat loss and hunting, but it is now more stable and secure. Introduced to Maria Island, Tasmania, during 1969-1970. Studies are needed in order to determine the triggers of facultative pre-partum estrus and embryonic diapause. A greater understanding of the biology of northern populations and ranging behavior in a variety of landscapes would also be useful.

Bibliography. Abbott & Burbidge (1995), Banks (2001), Bell (1973), Best, Blomberg & Goldizen (2015), Best, Dwyer et al. (2014), Best, Joseph & Goldizen (2013), Best, Seddon et al. (2013), Bond & Jones (2008), Calaby & Grigg (1989), Calaby et al. (1962, 1963), Carter, Macdonald et al. (2009), Caughley (1964a, 1964b), Caughley, Grice et al. (1988), Caughley, Short et al. (1987), Clarke et al. (1989), Coulson (1978, 1990, 1997a, 1999, 2001, 2008b, 2009), Coulson & Croft (1981), Coulson, Alviano et al. (2000), Coulson, Cripps & Wilson (2014), Davis et al. (2008), Dawson & Flannery (1985), Dawson, McTavish & Ellis (2004), Dawson, McTavish, Munn & Holloway (2006), DOE (2012), Duncan (1992), Eldridge & Rath (2002), Gélin et al. (2015), Grant (1973, 1974), Griffiths & Barker (1966), Griffiths et al. (1974), Groves (2005b), Hayman (1989), Heathcote (1987), Hill (19814, 1981b, 1982), Hill et al. (1988), Hohn et al. (2000), Jackson & Groves (2015), Jaremovic & Croft (1987 1991a, 1991b), Jarman (1987 1991, 1994), Jarman & Coulson (1989), Jarman & Phillips (1989), Jarman & Southwell (1986), Jarman & Taylor (1983), Johnson (2003), Kaufmann (1975), Kirkpatrick & McEvoy (1966), Le Gall-Payne et al. (2015), Letnic & Crowther (2013), Maguire et al. (2006), Maxwell et al. (1996), McAlpine et al. (1999), Mc-Cullough & McCullough (2000), Meers & Adams (2003), Menkhorst & Knight (2001), Miller, Eldridge, Cooper & Herbert (2010), Moore et al. (2002), Munny et al. (2008), van Oorschot & Cooper (1989), Payne & Jarman (1999), Pearse (1981), Poole (1975, 1982, 1983), Poole & Catling (1974), Pople et al. (2010), Quin (1989), Ramp & Coulson (2002, 2004), Rioux-Paquette et al. (2015), Schmidt et al. (2010), Short & Grigg (1982), Southwell (1984a, 1984b, 1987a), Taylor (1982, 1984, 1985b), Viggers & Hearn (2005), Wallis (1989), Woolnough & Johnson (2000), Yom-Tov & Nix (1986), Zenger et al. (2003).

Figures

47. Eastern Grey Kangaroo (Macropus giganteus), 48. Western Grey Kangaroo (Macropus fuliginosus), 49. Red Kangaroo (Osphranter rufus), 50. Black Wallaroo (Osphranter bernardus), 51. Antilopine Wallaroo (Osphranter antilopinus), 52. Common Wallaroo (Osphranter robustus), 53. Whip-tailed Wallaby (Notamacropus parryi), 54. Agile Wallaby (Notamacropus agilis), 55. Red-necked Wallaby (Notamacropus rufogriseus), 56. Western Brush Wallaby (Notamacropus irma), 57. Black-striped Wallaby (Notamacropus dorsalis), 58. Tammar Wallaby (Notamacropus eugenii), 59. Parma Wallaby (Notamacropus parma)

Distribution. E Australia from Cape York Peninsula, NE Queensland, S to far SE South Australia, and NE Tasmania; also on islands of Bribie, Curtis, Fraser, and North Stradbroke (Queensland), as well as islands of Little Snake, Rotamah, and Sunday (Victoria).