Kangaroo Island

[Alkirna Tours <>]

Hi Everybody

The mention of Powerful Owls as a possible control measure for the over
population of native marsupials on KI has provoked quite a deal of
discussion. At the risk of being classified as a bit of a screwball
another option to try and restore some semblance of balance in the KI
environment could be to RE introduce Tasmanian Devils and quolls into the
bushland here.

I have lived on KI for over ten years working at times for National Parks
and mostly in the eco-tourism field. The estimated population of Tammar
Wallabies on KI according to an Adelaide University researcher is
somewhere between 500 000 and 1 000 000 a gross overpopulation caused by
the conversion of about 55% of the islands original 100% bushland to
farmland. If one inspects bushland adjacent to farmland where large
numbers of wallabies and kangaroos feed at night the bushland is severely
damaged due to the large numbers of animals resting, browsing  and
just breaking down the native vegetation in that area.
 
I have driven around a farmers stubble paddock at night and observed in a
few minutes 25 or more Brush-tailed Possums foraging on the ground across
the stubble and generally across the island there are huge numbers of
possums. The biggest single factor in the decline of the Glossy Black
Cockatoo has been shown to be predation by BT Possums on eggs and
nestling young, just excluding possums from every GB Cockatoo nest that
could be found on the island led to an approximate fourfold increase in
the numbers of young fledging. The effect of possums on GB Cockatoos was
noticed because of the birds are such an obvious species. If predation by
possums is having such a massive impact on GB Cockatoos then it would be
almost certain that predation by possums would be impacting on many other
bird species on the island.

The behaviour of BT Possums here is very noticeably different to on the
mainland, on KI the possums spend much of their time foraging on the
ground, climbing trees to feed or when startled. This would appear to be
due to the total absence of predators at ground level for the possums
during the night, whereas on the mainland there were thylacines followed
by dingoes followed by foxes.

Bones collected from caves on KI show that in the past Tasmanian Devils,
Eastern Quolls and Spotted Tailed Quolls had lived here but had
apparently died out before Europeans arrived. The extreme overpopulation
of wallabies and BT Possums on the island could potentially be pushed
back towards a more balanced situation by the injection of some native
predators into the equation. Obviously a very close look would need to be
taken at the repercussions that may occur  with other native species
here but I think it would be foolish to reject the idea just because
those predators were not present when Europeans arrived in 1802. Kangaroo
Island is a very different place today to what it was in 1802.

Just a short comment re Koalas, the species of eucalypts that are being
wiped out are specifically the varieties that Koalas are foraging on and
non target eucalypts adjacent are in apparently perfect condition. Yes
the trees will regrow their leaves, I have watched Manna Gums stripped
and then soon as some new leaves appear Koalas are again in the tree
stripping off the flush of new growth giving the tree no time to recover
in due course the trees were dead.  It is not uncommon to see 5
Koalas in one tree of the favored varieties, when suggestions are that a
Koala needs more than 30 large eucalypts to be able to forage
sustainably. I doubt that intoduction of any native predators would help
control Koalas, if we do not cull them it is highly likely we will see
the wiping out of the varieties of large eucalypts favored by the Koalas,
thousands of Koalas starving to death and the loss of the habitat that
many other species depend on. 

I am uncertain what impact Devils and Quolls would have on  the
plague of feral cats we have here, they could possibly help reduce cat
numbers by competition and predation?

Cheers 
Ken Grinter

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