The
red kangaroo (
Macropus rufus) is the largest of all
kangaroos, the largest terrestrial
mammal native to
Australia, and the
largest extant
marsupial. It is found across mainland
Australia, avoiding only the more fertile areas in the south, the east coast, and the northern rainforests.
Male at
Melbourne Zoo
Description
Female red kangaroo at Botanic Garden Zoo in
Wagga Wagga, Australia
This species is a very large kangaroo with long, pointed ears and a
squared-off muzzle. Males have short, red-brown fur, fading to pale buff
below and on the limbs. Females are smaller than males and are
blue-grey with a brown tinge, pale gray below, although arid zone
females are colored more like males. It has two forelimbs with small
claws, two muscular hind-limbs, which are used for jumping, and a strong
tail which is often used to create a tripod when standing upright. The
red kangaroo's legs work much like a rubber band, with the
Achilles tendon
stretching as the animal comes down, then releasing its energy to
propel the animal up and forward, enabling the characteristic bouncing
locomotion. The males can cover 8–9 m (26.2–29.5 ft) in one leap while
reaching heights of 1.8–3 m (5.9–9.8 ft), though the average is
1.2–1.9 m (3.9–6.2 ft)
[3][4]
Males grow up to a head-and-body length of 1.3–1.6 m (4.3–5.2 ft)
with a tail that adds a further 1–1.2 m (3.3–3.9 ft) to the total
length. Females are considerably smaller, with a head-and-body length of
85–105 cm (33–41 in) and tail length of 65–85 cm (26–33 in).
[4][5]
Females can weigh from 18 to 40 kg (40 to 88 lb), while males typically
weigh around twice as much at 55 to 90 kg (121 to 198 lb).
[5][6] The average red kangaroo stands approximately 1.5 m (4.9 ft) tall to the top of the head in upright posture.
[7]
Large mature males can stand more than 1.8 m (5.9 ft) tall, with the
largest confirmed one having been around 2.1 m (6.9 ft) tall and weighed
91 kg (201 lb).
[6]
The red kangaroo maintains its internal temperature at a point of
homeostasis about 36 °C (97 °F) using a variety of physical,
physiological, and behavioral adaptations. These include having an
insulating layer of fur, being less active and staying in the shade when
temperatures are high, panting, sweating, and licking its forelimbs.
The red kangaroo's range of vision is approximately 300° (324° with about 25° overlap), due to the position of its eyes.
[8]
Ecology and habitat
Red kangaroo in an arid environment
Red kangaroo at Desert Park, Alice Springs
The red kangaroo ranges throughout western and
central Australia.
Its range encompasses scrubland, grassland, and desert habitats. It
typically inhabits open habitats with some trees for shade.
[9]
Red kangaroos are capable of conserving enough water and selecting
enough fresh vegetation to survive in an arid environment. The
kangaroo’s kidneys efficiently concentrate urine, particularly during
summer.
[10] Red kangaroo primarily eat green vegetation, particularly fresh grasses and
forbs, and can get enough even when most plants look brown and dry.
[11] One study of kangaroos in Central Australia found that green grass makes up 75–95% of the diet, with
Eragrostis setifolia dominating at 54%. This grass continues to be green into the dry season.
[12] Kangaroos also primarily consumed this species, along with
Enneapogon avanaceus, in western New South Wales where they comprised much as 21–69% of its diet according to a study.
[13] During dry times, kangaroos search for green plants by staying on open grassland and near watercourses.
[11] While grasses and forbs are preferred, red kangaroos will also eat certain species of
chenopods, like
Bassia diacantha and
Maireana pyramidata, and will even browse shrubs when its favoured foods are scarce.
[11] However, some perennial chenopods, such as round-leaf chenopod
Kochia are avoided even when abundant.
[14]
At times, red kangaroos congregate in large numbers; in areas with
much forage, these groups can number as much as 1,500 individuals. Red
kangaroos are mostly
crepuscular and nocturnal, resting in the shade during the day.
[15]
However, they sometimes move about during the day. Red kangaroos rely
on small saltbushes or mulga bushes for shelter in extreme heat rather
than rocky outcrops or caves.
[11]
Grazing takes up most of their daily activities. Like most kangaroo
species, they are mostly sedentary, staying within a relatively
well-defined home range. However, great environmental changes can cause
them to travel great distances.
[11] Kangaroos in New South Wales have weekly home ranges of 258–560 ha, with the larger areas belonging to adult males.
[16] When forage is poor and rainfall patchy, kangaroos will travel 25–30 km to more favourable feeding grounds.
[13]
Another study of kangaroos in central Australia found that most of them
stay close to remaining vegetation but disperse to find fresh plants
after it rains.
[17]
The red kangaroo is too big to be subject to significant non-human
predation. They can use their robust legs and clawed feet to defend
themselves from attackers with kicks and blows. However,
dingoes and
eagles will kill and eat
joeys.
Joeys are thus protected in their mother's pouch. The red kangaroo
formerly did have major predators that are now extinct. Extinct
predators included the
marsupial lion,
Megalania, and the
wonambi. Kangaroos are adept
swimmers,
and often flee into waterways if threatened by a predator. If pursued
into the water, a kangaroo may use its forepaws to hold the predator
underwater so as to
drown it.
[18]
Behaviour
Mob of red kangaroos at the Wagga Wagga Botanic Gardens
Red kangaroos live in groups of 2–4 members. The most common groups are females and their young.
[11] Larger groups can be found in densely populated areas and females are usually with a male.
[19]
Membership of these groups is very flexible, and males (boomers) are
not territorial, fighting only over females (flyers) that come into
heat. Males develop proportionately much larger shoulders and arms than
females.
[20] Most agonistic interactions occur between young males, which engage in ritualised fighting known as
boxing.
They usually stand up on their hind limbs and attempt to push their
opponent off balance by jabbing him or locking forearms. If the fight
escalates, they will begin to kick each other. Using their tail to
support their weight, they deliver kicks with their powerful hind legs.
Compared to other kangaroo species, fights between red kangaroo males
tend to involve more wrestling.
[21] Fights establish dominance relationships among males, and determine who gets access to estrous females.
[11]
Alpha males make agonistic behaviours and more sexual behaviours until
they are overthrown. Displaced males live alone and avoid close contact
with others.
[11]
Reproduction
The red kangaroo breeds all year round. The females have the unusual
ability to delay birth of their baby until their previous Joey has left
the pouch. This is called
embryonic diapause. Copulation may last 25 minutes.
[21]
The red kangaroo has the typical reproductive system of a kangaroo. The
neonate emerges after only 33 days. Usually only one young is born at a
time. It is blind, hairless, and only a few centimetres long. Its hind
legs are mere stumps; it instead uses its more developed forelegs to
climb its way through the thick fur on its mother's
abdomen
into the pouch, which takes about three to five minutes. Once in the
pouch, it fastens onto one of the two teats and starts to feed. Almost
immediately, the mother's
sexual cycle
starts again. Another egg descends into the uterus and she becomes
sexually receptive. Then, if she mates and a second egg is fertilised,
its development is temporarily halted. Meanwhile, the neonate in the
pouch grows rapidly. After approximately 190 days, the baby (called a
joey)
is sufficiently large and developed to make its full emergence out of
the pouch, after sticking its head out for a few weeks until it
eventually feels safe enough to fully emerge. From then on, it spends
increasing time in the outside world and eventually, after around
235 days, it leaves the pouch for the last time.
[22]
While the young joey will permanently leave the pouch at around
235 days old, it will continue to suckle until it reaches about
12 months of age. A doe may first reproduce as early as 18 months of age
and as late as five years during drought, but normally she is two and a
half years old before she begins to breed.
[23]
The female kangaroo is usually permanently pregnant, except on the
day she gives birth; however, she has the ability to freeze the
development of an embryo until the previous joey is able to leave the
pouch. This is known as
diapause,
and will occur in times of drought and in areas with poor food sources.
The composition of the milk produced by the mother varies according to
the needs of the joey. In addition, red kangaroo mothers may "have up to
three generations of offspring simultaneously; a young-at-foot suckling
from an elongated teat, a young in the pouch attached to a second teat
and a blastula in arrested development in the uterus".
[21]
The kangaroo has also been observed to engage in
alloparental care,
a behavior in which a female may adopt another female's joey. This is a
common parenting behavior seen in many other animal species like
wolves, elephants and
fathead minnows.
[24]
Relationship with humans
A red kangaroo crossing a highway
The red kangaroo is still an abundant species and like all
Australian wildlife
is protected by legislation. It has even benefited from the spread of
agriculture and creation of man-made waterholes. However competition
with livestock and rabbits poses a threat. It is also sometimes shot by
farmers as a pest although a "destruction permit" is required from the
relevant state government.
Kangaroos dazzled by headlights or startled by engine noise often
leap in front of vehicles, severely damaging or destroying smaller or
unprotected vehicles. The risk of harm to vehicle occupants is greatly
increased if the windscreen is the point of impact. As a result,
"kangaroo crossing" signs are commonplace in Australia.
Commercial use
The kangaroo is so numerous that there is regulated harvest of its hide and
meat.
Hunting permits and commercial harvesting are controlled under
nationally approved management plans, which aim to maintain red kangaroo
populations and manage them as a renewable resource. Harvesting of
kangaroos is controversial, particularly due to the animal's popularity.
[23]
In the year 2000, 1,173,242 animals were killed.
[25] In 2009 the government put a limit of 1,611,216 for the number of red kangaroos available for commercial use. The
kangaroo industry is worth about
A$270 million each year, and employs over 4000 people.
[26] The kangaroos provide meat for both humans and pet food. Kangaroo meat is very lean with only about 2% fat. Their skins are
used for leather.
Conservation
