| As well as such well known animals
as kangaroos and wallabies,
the family Macropodidae includes less familar marsupials, such as
tree kangaroos, pademelons, quokkas,
bettongs and potoroos.
Ancestral macropods were forest dwelling browsers. Modern macropods are
adapted to a range
of habitats; woodlands, forests, rocky outcrops, cliffs and plains.
The desert-adapted, grass-eating kangaroos arose some 5 -1 5 years mya.
Traditionally large and small species were called wallabies
and kangaroos respectively, nowadays the name 'kangaroo' covers them both.
Ecologically macropods fill the niche of antelopes, deers and horses,
having evolved lightened, long limbs with reduced toes that enable them
to cover long distances over open ground at speed to evade predators.
|Typically macropods have:
- small deer-like heads with wide set eyes and binocular vision,
prominent upright ears which rotate to hear in all directions;
- a moderately long muzzle with a split upper lip;
- diprotodont dentition;
- thin necks;
- short forelimbs with mobile grasping forepaws that can
hold food, open the pouch and box;
- strongly developed hindquarters;
- long hind limbs, with the characteristic long narrow
feet which gives them the name of 'macropod' or 'big-foot';
- syndactylous hind-feet: the second and third digits are fused
together to form a grooming comb;
- large heavy tails.
Kangaroo Island Kangaroo, a subspecies of the Western Gray Kangaroo (Macropus fuliginosus)
| Most members of the family travel by hopping,
taking off on their hind feet, landing on their fore limbs
and tail, pushing off again with their hind limbs. The
elongated and very strong fourth
toe of the hind foot serves
as a lever to propel the animal along and bears the animal's weight
when it stands. Long legs increase the stride
when hopping. Forelimbs and tails prop them up when they crawl
slowly to feed. Powerful hind limbs and large heavy tail serve for balance and support.
Tree kangaroos have shorter prehensile tails and climb rather than hop.
Our skeleton of a red kangaroo shows the distinctive features
which enable macropods to hop and crawl along:
the pelvis is upright, long and narrow;
the thighs are long and muscular;
the shin bones are elongate but not heavily muscled;
the ankle is adapted to prevent the foot rotating
sideways and the ankle being twisted;
the tail is a counterbalance and prop;
The epipubic bones can be seen protuding from the front of the pelvis:
a feature of monotremes and marsupials, their function is not known!.
Red kangaroo skeleton ( Macropus rufus)
Many kangaroo species are grazers and browsers adapted to living in dry desert
muzzles, teeth and tongues are adapted to
taking small food items. Their digestive physiology and a large stomach,
with several chambers for fermentation, can process poor quality
|Kangaroo skull: The basic dental formula of adult animals is
I3/1; C0/0; PM variable; M4/4|
Kangaroos'skulls and dentition
show special adaptations to feeding on an abrasive diet of grass.
Kangaroos' reproductive biology can cope with periods of drought
and lack of food. Macropods have an embryonic diapause that allows
the young to grow to a certain stage before another is born.
Most species have about three litters at a time: one in the uterus,
one attached to a teat in the characteristic, well-developed pouch; one out of the
pouch but still being cared for by the mother. The mammary glands produce
qualities of milk for the two suckling young; the two teats of the gland
being under different hormonal control.
- an arc of blade-like upper incisors surrounds a fleshy pad
at the front of the palate;
- the two procumbent lower incisors hold leaves against the pad;
- the leaves are stripped off against the edge of the arc of the upper
- canines are absent and the diastema between the incisors stores food before
it is passsed to the molars;
- cheek teeth are:
- reduced in number;
- have transverse ridges to process hard grasses
- the unspecialised premolars and molars of large kangaroos
erupt sequentially at the back of the mouth and are shed as they wear out,
like elephants' teeth.
- other macropods have persistent premolars
and four erupted molars which wear out simultaneously.
Most species of macropods are relatively abundant. Some,
such as several tree kangaroos, are threatened, but others,
like the grey and red kangaroos, have flourished and are now
considered to be pests.