Interesting facts about kangaroos and their kind
Most species increase their reproductive rate by having three overlapping
generations: a diapausing blastocyst (about 100-cell embryo) in utero, a pouch
young and a young-at-foot. Each of these may have a different father and so
sibling rivalry is expected to be intense. Even so there is no evidence that the
young-at-foot directly interferes with the pouch young even though it puts its
head back into the pouch to suckle from one of the other four mammary glands
until weaning. The majority of species have the capacity to be ‘perpetually
pregnant’ from sexual maturity until death.
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Like all herbivorous mammals, the kangaroo family suffer high tooth wear from
the silicates in grasses. As a molar wears it moves forward in the tooth row and
may eventually be shed to be replaced by a new emergent molar. The latter are
limited so eventually a very old individual will run out of teeth. The exception
is the Nabarlek which continues to produce molars to cope with a diet of ferns
growing on sandstone.
One of the most sociable species of kangaroo is found in the Top End (wet-dry
tropics) of Australia. The Antilopine Wallaroo forms large aggregations and
individuals whether male or female regularly allogroom (e.g. one grooms the neck
and shoulders of another), lean on each other and lie resting in contact.
Several species have long-term associations between female kin forming a
matriline of mothers, daughters, grand-daughters etc.
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©Ulrike Kloecker |
Young of all species are extremely playful. When they exit the pouch they will
hop in circuits around their mother or dash off and back at full speed. En route
they may bat at shrubs and trees and return to their stoic mother and give her a
clip on the ears.
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©Ulrike Kloecker |
Few species show strong territorial behaviour but shelter sites like rock
overhangs and caves for Rock-wallabies and the nests of Potoroos and Bettongs
may be strongly defended. In most of the larger species males and females freely
intermingle in open membership mobs. Even so competition amongst male kangaroos
for dominion over other males for mating opportunities with females in their
home range is intense. Size and reach matter and fights are usually swift and
decisive. However, boxing matches are a frequent occurrence amongst all male
size classes and they cooperate to exercise fighting skills. The evidence for
this comes from observations of self-handicapping where a larger male may stand
flat-footed to engage a smaller one and suffer kicks from the latter without
resorting to a king hit (kick). The abdomen of males has thickened skin (dermal
armour) to provide some protection against raking toe nails.
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The macropods evolved around 16 million years ago from a possum-like ancestor
and familiar species like Eastern Grey Kangaroos have been around for a few
million years. The Red Kangaroo is one of the more recently evolved species but
still has a million year history on the continent. Contemporary writers and
commentators often state that there have never been more kangaroos of some
species than now following the introduction of European farming practices a few
hundred years ago. With the long evolutionary history of the macropods in
Australia it is rather presumptuous of such people to claim that a species has
never been in a region or in a particular abundance. Exaggerated claims of
kangaroos in ‘plague proportions’ or as overabundant species are propaganda to
support lethal control measures or to justify commercial exploitation of meat
and hide products. Six species are extinct and many have suffered massive range
contractions since European colonisation of Australia. Have the macropods really
never had it so good?
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The macropods include species that live in burrows and ones that live in trees.
You can find them hopping in the snow, seashore and desert. The species with the
largest longitudinal range is the Common Wallaroo which is pan-continental but
absent from Tasmania. The Eastern Grey Kangaroo has the largest latitudinal
range from northern Tasmania to Cape York. The smallest range is a single
population of the recently rediscovered Gilbert’s Potoroo. Actions to establish
a second island population are underway and hopefully will achieve the same
success as reintroduction of the Bridled Nailtail Wallaby which suffered a
similar plight.
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