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RE: crocs eating hadrosaurs (was Gr. 9 sci proj)



>----------
>From:  Wayne Anderson[SMTP:wander@hooked.net]

...

>        What we're really looking at here is a species whose role is predator
>fodder. Rabbits are prolific because they can: A) run, B) hide, and (most im-
>portantly) C) BREED LIKE HELL. I realize edmontosaurs aren't rabbits, but if
>you look at what is known of Maiasaur breeding (the best known hadrosaur
>for that subject), it sure looks like they bred like hell. Giant nesting
>grounds,
>wall-to-wall with nests and mother dinos nose-to-tail. A nest Jack Horner re-
>constructed had at least 23 eggs in it (see photo in _Digging Dinosaurs_,
>color
>plate 7). Another nest was found with the remains of 15 hatchlings. If we can
>assume that most hadrosaurs had similar habits (not a safe assumption, but
>it's the only data I have), then edmontosaurs were also prolific breeders.
>So when you say they were doing something right, what they were doing is
>what any successful herbivore does: breed enough to balance predation.

In fact, hadrosaurs and indeed most dinosaurs, appear to have had much
greater reproductive capacity than large mammals.  The analogy with
rodents is actually quite appropriate - in fact they have had even
higher capacity (fecundity) than rabbits.

Large mammalian herbivores like wildebeest, zebra, elk, bison etc.
typically carry only a single baby per year - in fact, the only large
mammal that has one than one young on a regular basis is the moose which
often has twins.   Really large mammals like elephants and whales have
such long gestation times, and then long nursing times that they have
one baby every 3 years.

Compare this to hadrosaurs which typically have egg clutchs of 15-20
eggs.   They were able to do this because the resouces per egg are so
small - even the biggest dinosaurs appear to have come from eggs that
weigh only 1 to a couple kilograms. It is possible that they only laid
eggs once every several years, but there is no compelling evidence that
this was biologically necessary.  In fact, they could have laid a clutch
more often than once a year in some favorable ecosystems.

Bjorn Kuretin, and other mammalian paleontologists have specualted that
mammalian reproduction is a fundamental limiting factor that has limited
mammals (particularly terrestrial mammals) to smaller sizes (generally
speaking) than the upper limits for dinosaurs.

Nathan


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