The antilopine wallaroo is this country’s
only large kangaroo that lives entirely in the tropics. Unlike some
kangaroo species, its numbers aren’t in great abundance and
it may even be under threat. CRC PhD student Euan Ritchie is
studying its biology so we can develop conservation and management
regimes that will help it survive.
The antilopine wallaroo is Australia's only
large tropical kangaroo Photo: David Webb
Behaviour | Distribution | Wallaroo snapshot | Cape York
biodiversity | Stakeholder
cooperation | More Reading |
Macropods are among Australia’s most recognisable group of
marsupials; they include kangaroos, tree kangaroos, wallaroos,
wallabies, rock wallabies, bettongs, potoroos and the quokka. Of
Australia’s 50 recent macropod species, six are now extinct
and 11 are declining (Johnson et al. 1989).
Until recently it was thought that the fauna of
Australia’s monsoonal tropics remained largely intact. But at
present a large-scale mammal decline appears to be occurring
throughout this region, particularly within savanna environments.
Researchers such as John Woinarski warn that past extinctions in
central Australia were extremely rapid, with changes in abundance
leading to the loss of species within one to two decades. Further
work by Don Franklin details widespread declines of granivorous
birds that overlap those areas with reported mammal declines.
Within the vast area of Cape York and the Einasleigh Uplands
(Figure 2) lives one of Australia’s most distinctive animals:
the antilopine wallaroo ( Macropus antilopinus ). When Gould
(1842) named the wallaroo he thought they resembled Africa’s
antelopes: the males have a brick red colour on their back
extending all the way to their head, with their front a vivid
creamy white. Gregarious, grass-eating and tropical, antilopine
wallaroos also occur in smaller numbers in the Top End of the
Northern Territory and the Kimberley region of Western
However, observations in Cape York Peninsula have shown
widespread mammal declines, including declines of antilopine
wallaroos. So at a time when it seems there are kangaroos
everywhere and they are being culled in certain parts of Australia,
this particular species is under threat—and it may be the
first observed decline of a kangaroo since European settlement.
Photo: David Webb
There are a number of potential causes for these declines:
habitat change and clearance, introduced predators and competitors,
intensification of grazing and agriculture, introduction of exotic
diseases, changes in fire regimes and overkill.
Of the six living species of kangaroo, none have been listed as
endangered to date. Typically kangaroos have prospered as a result
of the land management practices associated with livestock grazing,
such as permanent water sources being established, woodland being
cleared in favour of grasslands and the removal of predators,
particularly dingoes. However, like many mammal species of northern
Australia there is very little known about the wallaroo: its diet,
breeding habits, biology—all are something of a mystery. This
means we have no basis to interpret the causes of the declines that
have been observed, or to recommend appropriate management of
habitat to prevent further declines.
Given that the antilopine wallaroo is harvested as a bush food
by Aboriginal communities, our estimates of population size,
distribution and reproductive rates will allow us to estimate
sustainable harvest rates. The study will also result in a better
understanding of recent ecological changes on Cape York Peninsula,
and their effects on wildlife.
Figure 1: Distribution of
antilopine wallaroos: Dark blue represents the species core
distribution and light blue the periphery. Dots represent known
locations of antilopine wallaroos.
Figure 2: Queensland distribution of antilopine
The animal is quite striking and beautiful to look at; but over
the course of my study, I’ve noted something even more
striking: antilopine wallaroos display a behaviour known as sexual
segregation. Outside of the breeding season, these wallaroos
separate into single sex groups with large groups of females
(5–10 individuals) and bachelor groups comprising large-sized
males (3–5 individuals).
Why do they do this? Some theorise that females make different
diet choices because their reproductive role and smaller body size
means they have higher relative energetic needs—but activity
patterns and risk of predation could also play a part.
My observations have confirmed that diet choice may indeed play
a significant role. While both males (85%) and females (74 %) feed
on large amounts of grass, females feed on significantly more
forbs, which have a higher nutrient content than grass. Within my
study site, forbs were less abundant and more patchily distributed
than grass, so this could explain the group splitting between males
and females. However, other mechanisms could also offer
explanations, so more research is needed.
Because of this split between male and female, males spend long
amounts of time with each other, some of which is spent
establishing a dominance hierarchy, which seems to be related to
reproductive success. The hierarchy determines which male in any
chosen group is the strongest, and therefore most likely to succeed
in male versus male competition for females, and ultimately who
will mate with females in the breeding season.
Cape York Peninsula is about 13.5 million
hectares in size and encompasses a diverse array of habitats and
associated flora and fauna. Mammal species recorded as declining
include the black footed tree rat, northern quoll, common brushtail
possum, rufous bettong, some rock wallabies and the antilopine
wallaroo (John Winter, Christopher Johnson & Peter Johnson,
pers. comm., 2002).
The study is being conducted at two scales:
broadly across the whole of the Cape and Einasleigh Uplands and
locally in Mount Surprise (Figure 2). At the broad scale the Cape
and Einasleigh Uplands are divided into three regions, southern
(Mount Surprise, Georgetown and Chillagoe areas), middle (Laura,
Coen, Mungkan Kandju and LakefieldNational park) and northern
(Weipa and surrounds).
Wallaroos or kangaroos—what’s
in a name?
The name ‘kangaroo’ usually refers
to the large macropods of the grassy plains like the red and grey
kangaroo. ‘Wallaroo’ is a name used for macropods that
are smaller than kangaroos but larger than wallabies, and that
often prefer hillier country. Male antilopine wallaroos can weigh
up to 50–60 kilos with females about half that size. Because
of their large size antilopine wallaroos are sometimes also called
Over the past 12 months I have recorded almost 3000 wallaroos,
and it appears that population numbers are relatively stable in
Queensland—interestingly, the area with the highest abundance
is on a cattle station that is cell grazed—an unusual grazing
practice in Cape York—and has not been burnt for 10 years.
This could mean that the antilopine wallaroo is sensitive to
However, my findings are no cause for complacency, because
wallaroos are most abundant in the better grazing lands of north
Queensland around the basalt belt of Mount Surprise (Figure 2).
This could eventually be a problem for graziers who want to expand
their business while preserving habitat for native species such as
the wallaroo. Numbers in the Kimberley and Northern Territory do
not fare as well, but more research is needed to pin down the
probable causes for declines in those regions.
The nature of my work requires interaction with a broad spectrum
of individuals and communities, including graziers, Indigenous
people, and park rangers. The cooperation between these groups has
been inspiring, and I am thankful that this is the case, as these
are the people who will shape the future of our tropical
An article on Euan’s findings will also appear in the
next issue of Nature Australia , due out in
Croft, D.B. 1987, ‘Socio-Ecology of the
Antilopine Wallaroo Macropus Antilopinus in the Northern
Territory Australia with Observations on Sympatric
Macropus-Robustus-Woodwardii and Macropus-Agilis’,
Australian Wildlife Research , 14(3) 243–256.
Russell, E.M., & Richardson, B.J. 1971,
‘Some observations on the breeding, age structure, dispersion
and habitat of populations of Macropus robustus and
Macropus antilopinus (Marsupialia)’, Journal of
Zoology , London 165:131–142.
Woinarski, J.C.Z., Milne, D.J. &
Wanganeen, G. 2001, ‘Changes in mammal populations in
relatively intact landscapes of Kakadu National Park, Northern
Territory, Australia’, Austral Ecology ,