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Re: Island-dwelling dinosaurs (was Re: Gargantuavis neck vertebra)
On Wed, Jun 20th, 2012 at 4:50 AM, David Marjanovic <email@example.com>
> I'd like to add:
> -- "(except Cassowary)", you write -- yes, what about the cassowaries?
> How do they (3 species last time I checked) keep their nests from being
> plundered by goannas too often?
By being complete and utter 'bad-asses' (to use a Holtz-esque phrase). Nothing
in its right mind
goes near a male cassowary sitting on eggs. Or with chicks in tow. Or at any
time really. They'll
attack anything that dares to look sideways at them.
> -- "Hunt down" isn't a term I'd apply to "nesting sites".
> -- The timing of the extinction of Sparassodonta is not actually known
> to fit the Great American Interchange, AFAIK. That leaves thylacine vs.
> dingo as a sample of 1, and even there I have no idea what effect it had
> that people have been burning much of Australia down every year for some
> 50,000 years now.
It would seem that most of Australia's large flightless birds were extinct well
before dingos got into
the country. Even with dingos-a-plenty for a couple of millennia, emus (and
cassowaries) are still
with us though.
Thylacines may not have been any threat at all to the eggs of large flightless
specialised in eating only soft tissue, and seemed to have avoided tooth
contact with bone if at all
possible. The dentition seen in thylacine skulls is generally pristine even in
very old individuals, with
little (if any) signs of wear. Attempting to crack open the thick-shelled eggs
of large flightless birds
would seem to have been something they'd have avoided. Thylacines may well have
chicks though, and perhaps even adult birds. They certainly had no trouble
bringing down large
macropods, so fast-running bipeds with powerful kicks didn't seem to phase them.
One important difference between thylacine and dingo hunting strategies is that
to have been largely solitary, whereas dingos will hunt in large packs in areas
supporting them. Then again the larger the pack, the larger the area required
to sustain them, so
having a concentrated group of ten dingos defending a large territory against
predators might actually be better for the prey species than having ten
thylacines patrolling much
smaller individual territories. Modern ecological studies suggest that rare
marsupials do better in
areas where dingos exist than in areas without them, apparently because they
numbers of cats and foxes.
The real question is what impact thylacoleo had on flightless birds. Their
powerful jaws and 'big-ass'
shearing teeth (to paraphrase another Holtzism) would seem to make them far
more likely to
attempt egg theft than a thylacine. Yet clearly numerous flightless birds
managed to survive along
side them for a long time.
Once you throw Megalania into the mix, it would seem that large flightless
birds are (and were)
more than capable of dealing with all sorts of nest predators - let alone
predators willing to target
the adults themselves.
Spatial Data Analyst Australian Dinosaurs
Melbourne, Australia http://home.alphalink.com.au/~dannj