Re: Big Bakker article in June Discovery Mag

["Adam Britton" <abritton@wmi.com.au>]

From: <MariusRomanus@aol.com>
Sent: Thursday, May 01, 2003 8:19 AM

>>> The article goes on to explain his findings from 33 sites at Como
Bluff... How the teeth of adult and young allosaurs were basically the same,
meaning they ate the same things (unlike crocodilians which show a different
pattern)... Bones of prey exhibit baby and adult teeth marks... Baby teeth
are found shed with adult teeth, meaning they were eating in the same place,
feeding together... which leads to his "lairs", being not dens or nests, but
just a communal feeding area.<<<

That's an interesting article. Let me explain a scenario with Australian
freshwater crocodiles that really has nothing to do with allosaurs, but does
indicate alternative interpretations of finding large groups of teeth.

During the wet season, temperatures in northern Australia are consistently
high by day and night, prey are abundant, and crocodiles feed extensively.
Their stomachs are full of a variety of prey items. During these times,
crocodiles disperse out of river systems and across floodplains, essentially
following the margins of floodwaters. Most of their feeding occurs during
this time, and hence teeth shed during feeding are dispersed over a wide
area.

By contrast, during the dry season the water levels fall and the crocodiles
become increasingly concentrated in permanent bodies of water. The rivers
typically dry up and most crocodiles move to relatively small (eg. 50 x 100
metres) billabongs. While daytime temperatures are relatively warm, night
time temperatures fall substantially and prey depletes rapidly, the end
result being that these crocodiles eat virtually nothing for the majority of
the 6 month dry season. Stomach content analysis confirms this. However,
particularly in harsh dry seasons following poor wet seasons, many of these
permanent billabongs can dry out completely leaving crocodiles no choice but
to either find new water or estivate. Most mortality occurs during this time
particularly of younger animals. In addition, nesting occurs at the end of
the dry season. High levels of mortality of embryos and young juveniles are
typical.

Therefore, with Australian freshwater crocodiles, teeth and bones of various
size classes are found in very high concentrations in the bed of these
billabongs, deposited there during the dry season when feeding does not
occur. This scenario is exactly what's happening in our study site, a
population of around 4,000 animals we have 25 years of data from.

Obviously this is a very specific scenario for a particular species, but it
might perplex alien paleontologists examining crocodile remains here in a
million years time. Hopefully my bones won't also be amongst the remains -
now that would be confusing.

Best wishes,

Adam


--
Adam RC Britton | abritton@wmi.com.au
Senior Researcher | Wildlife Management International
Darwin, Australia | Tel 08 8922 4500 | Fax 08 8947 0678
wmi.com.au | crocodilian.com