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VARANID EATING HABITS



> Thanks to those who responded.  Graeme Barden's observations on Komodo 
> dragons suggests that while the construction of their skulls/jaws 
> theoretically (read that: "in my ignorance of what they're actually 
> like") would allow them to work like snake jaws (to a degree, anyway), the 
> animals don't actually use their jaws that way.  So much for inferring 
> behavior from anatomy!                            Norm King

I'm not sure this is correct, though perhaps I should've pointed it out to begin
with. Komodo monitors are well known amongst us theropod fans as 'infector
killers': the fairly large serrations on their teeth create 'pockets' in which
assorted micro-organisms live: the dragon bites and you live, you die of
septicemia. It's been inferred that the monitors might make a habit of killing
in this way, and I think Bill Abel (right?) has extended this notion to
tyrannosaurs. 

This may be valid in some cases, but I have difficulty in imagining the lizard
following a slowly dying victim for weeks, waiting for it to drop due to
terminal infection. As Jared Diamond is so fond of pointing out, blasting the
guts out of a victim in a quick attack is far more effective, and monitor
attacks on children suggest that this is really what goes on. 

I question comparisons made between the monitors and tyrannosaurs - not just for
the obvious reasons - but for a few technical things too. The layout of monitor
teeth differ substantially from those of tyrannosaurs (check it out in Weish-
Dod-Os) and komodo monitors also have a particularly unusual mechanism whereby
flexible 'gums' pull down over the teeth when the mouth closes. As the monitors
have serrated teeth, they actually lacerate these, and consequently their mouths
become drippy messes of pink ooze. Lovely. No-one (AFAIK) is too sure why this
happens, but maybe it encourages the growth of the pocket-dwelling bacteria _IF_
they are important to the hunting strategy. ONOH, perhaps it's just a design
flaw ;-).

But, from what I've seen, komodo monitors kill with a quick rush and slashing
bite. They're so strong that if they grab a potential victim in their mouths
they can move enough to do it some serious damage there are then (as opposed to
the idea that they rush in for a nip and then retreat). In humans they generally
go for the legs - in adults for about mid-thigh, in kids they grab around the
hips and do lots of damage in the process. People on Flores etc tend to live in
stilt-houses, and as they descend ladders to the ground they don't see monitors
lurking beneath. Attacks are moderately common.

Anyway, with regard to the distensible jaws bit, monitors have much flexibility.
The jaws can open to something like 80 degrees and the throat is highly
distensible. An interesting scene in 'Life on Earth' depicts interaction between
a feral dog and a monitor. A deer carcass (perhaps around 15 kg of dead meat,
a few legs still attached) is on the ground, and the dog is chewing off scraps
best it can. Along comes monitor. Dog barks. Monitor takes no notice. Monitor
grabs carcass, juggles it in its jaws and swallows it. The whole carcass. The
animal's jaws don't get widely distended, as in a python say (BTW, check out the
photo in the current Fortean Times of a 7 metre python trying to eat a man), but
a lot of kineticism must be going on, and the monitor's neck does get stretched
quite a bit. I'd say that they have highly distensible jaws.

For more info, there is a new book just published on the Komodo monitor, which
is obviously a complex and fascinating beast. I'll mail details if there' much
interest.
 
> Komodo dragons may be unique because of their large size.  Gila monsters 
> may be the best comparison with sphenodonts.  Does anybody have any 
> suggestions as to why sphendonts seem to have been so completely 
> outcompeted by lizards?  Is there anything besides skull kinesis that 
> seems likely?  Is my premise right--i.e., have they indeed been 
> outcompeted by LIZARDS?  How would we know?

Check out the lit. on the Triassic cave deposits in England. Sphenodonts were
as numerous and diverse as lizards are today early in the Mesozoic - perhaps
they lost the edge in one of the big events. Carroll (Vert. Palaeo.) has a bit
on the functional differences between the two groups, and this shows that
lizards have a 'better' directed bite on food in the jaws.
 
Incidentally, I always thought that there was only 1 recorded death by gila
monster bite. Turns out there are about 8, but all are a bit dubious in
interpretation.

"Got a quarter?"
"Want some candy?"

DARREN NAISH