Wombats
There
are three species of wombat;
The Common Wombat (Vombatus
ursinus) is widespread
and locally common from south east Queensland to Tasmanian.
It is declining in Western Victoria and South Australia. Length
to 1100mm, weight 20-35Kg, life span 5-15 years in wild (uncertain),
longer in captivity.
The Southern Hairy-nosed
Wombat (Lasiorhinus latifrons)
has a patchy distribution in semi-arid scrubland and mallee
from the far south east of WA to the far south west of NSW.
Population classified as vulnerable due to poor breeding conditions.
Length to 935mm, weight to 32Kg, life span to 12 years in wild
(estimated), longer in captivity).
The Northern Hairy-nosed
Wombat or Yaminon (Lasiorhinus krefftii)
is critically endangered, being restricted to about 70 individuals
in a 300 ha protected area in Qld. Probably the most endangered
of all large mammals. Length to 1100mm, weight to 35Kg, life span
as per SHN wombat. Struggling to survive because if invasion of
African buffel grass which out-competes the native grasses that
this wombat feeds on. Population now considered too small for
relocation of enough individuals to start a new colony. Captive
breeding attempts have proved largely a failure.
Evolution
Wombats are part of the family of large marsupials known as the
Diprotodontia. Their ancestors evolved some 55 to 26 million years
ago and included the diprotodon (giant wombat), one of which was
the largest marsupial to ever live, about the size of a hippopotamus.
When Aboriginal Australians arrived, approximately 55000 years
ago, these giant wombats were still common. It is thought that
hunting and habitat alteration brought about their extinction.
Ecology and behavior
Wombat gestation is between
21 and 25 days. At birth the 2 gramme 'joey' is blind deaf and
hairless. However, it has comparatively well developed forepaws
and uses these, along with a good sense of smell to crawl to the
mothers' pouch, whereupon it attaches itself to one of the two
available teats. Here the teat will expand, keeping the infant
secure. The joey will stay in the pouch for an average of 8 months,
whereupon it will start to venture out on its own and will also
begin to eat solids. Weaning is completed at around 20 months.
Wombats will stay with their mother for the first 2-3 years of
life.
Wombats have an extraordinarily slow metabolism. It takes about
2 weeks from when food is first eaten to when it is passed.
This enables them to extract the maximum nutrition from their
very poor diet (mainly grasses) and means they need to spend
less time foraging (approx 3-8 hours per day) than a comparable
sized kangaroo or ungulate. They are also able to obtain nearly
all of their water requirements from plant matter and dew.
Wombats generally move slowly. However, when required the can
accelerate rapidly and can reach speeds of up to 40km/h (25mph)
and can maintain that speed for up to 90 seconds. This is equivalent
to running 800 metres faster than an olympic athlete.
Wombats face few predators other than man. Dingoes and domestic
or feral dogs will attack wombats, as will foxes and devils in
Tasmania. Smaller wombats may be taken by larger birds of prey
and quolls.
Wombats have developed effective defences against predators.
Firstly their lower back is covered by a large cartilaginous
plate which is all but impenetrable to natural predators (they
also have a very short tail to aid protection when being attacked
from the rear). Thus they will present their rear when under
attack. If possible they will retreat to a burrow. They have
been known to trap a predator underground and crush it against
the tunnel roof until it is suffocated.
Wombats are thought to be relatively intelligent. Unlike koalas
(their nearest relative) they have large brains which completely
fill the cranial cavity. They also engage in play, thought be
a sign of higher intelligence. They are, however, quite antisocial.
Wombats dig larger tunnels than any other mammal. They have
remarkably strong forepaws and long claws and have been known
to dig tunnels up to 30 metres (100 feet) long. They will generally
rather dig through an obstacle than around it (such as fence
posts) and this, coupled with the threat to stock from collapsing
tunnels, has meant that in Victoria they are still regarded
as vermin and often shot.
Wombats and humans
The main threat to wombat comes from mankind. The main problem
is the destruction of natural habitat and the introduction of
animals which compete with them for food (sheep, cattle). Many
wombats are also killed on roads.
Wombats make poor pets and indeed it illegal to do so in Australia.
They are usually quite passive and appear to have little fear
of humans. However, this lack of fear means that they will turn
aggressive if provoked, and with large incisors and strong paws
they can easily inflict injuries.
Recommended
reading
The Secret Life of Wombats, James Woodford, Text Publishing
2001 |
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