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(Long) word from the sole "non-stealthy egg" believer



Ron Orenstein says: "Mr. Bois, please provide me with one shred
of genuine evidence that dinosaurs were unable to protect their
eggs adequately."

     If I had this, we wouldn't be discussing it.  But some
things must be true even though we have no evidence for them.
For example, dinosaurs had red blood.  We can't observe this but
we can infer it from what we know about vertebrates etc..
Similarly, I can say some things about dino reproduction that
must be true.  You can only do one of two things if you lay eggs:
hide them or defend them.  This is a fact!  You cannot just leave
them lying around because they will be eaten.  And, if you can't
hide them--and let us restrict our argument to big dinos--then
defending them _must_ be a problem simply because things bigger,
meaner, and nastier than you push you off your nest and eat your
eggs.  Fighting back runs the risk of injury.  This is a fact and
a problem.  You can run away and abandon your nest, but this gets
expensive especially since, if birds are in any way a model, good
nesting sites are hotly contested.
     Big dinosaurs _must_ either stand and fight or abandon the
nest.  This deficiency is seen in stark contrast with placental
reproduction.  Placentals can just run away from a predator
keeping baby safe inside.  I think you have criticized this view
in the past claiming that pregnant mothers are subject to
increased predation.  If so it is you who must provide evidence.
For my part I provide Jason Lillegraven's authority
(_Reproduction in Mesozoic Mammals_ in Mesozoic Mammals,  ed. by
Lillegraven et al).  Comparing efficiency of placental vs.
marsupial baby carriage he says: "Placental fetuses...are kept in
a firm support sling near the mother's center of gravity and
balance.  She is still usually capable of high rates of activity
involving hunting, running, turning, and great migrations, even
at near term stages of pregnancy.  I have seen few data
suggesting that predation is significantly higher in pregnant
eutherians than in nonpregnant individuals...Thus, although a
pregnant eutherian does have a noticeably swollen abdomen, the
support of developing young is excellent, the overall locomotory
fitness of the mother is not greatly reduced, the fetus is
protected from desiccation, and the young is developed into an
advanced morphological state at a sustained high rate`under
conditions of maternal core body temperature.  All things
considered...the overall eutherian adaptive survival complex
suggests superiority."  And I would add that, at least in non-
stealthy niches, this mode has it all over the egg as well.
Mammals may or may not have played a role in dino nest predation.
But, inasmuch as they were able to simply run away from what I
believe was an increasing egg-predation load toward the end of
the K/T, they were the victors not in a war of direct
competition, but of reproduction--of survival of the fittest.

Ron Orenstein says: "Please provide me with one new egg predator
appearing close enough to the K/T that beat mechanisms that had
kept dinosaurs going in the presence of mammals for well over 100
million years."

     In addition to the already ambient egg predation of the
Cretaceous (in a time when there were more eggs there was bound
to be more egg-predation--in nature there is no such thing as an
unexploitable resource), new possible egg predators were indeed
developing towards its end.  Mammals: "In contrast (to the Early
Cretaceous eutherians [whose teeth] probably functioned best in
insectivory), the structural differentiation seen in the
dentitions and postcranial skeletons of Late Cretaceous forms
suggests the existence of diversified habits.  For example, the
teeth of North American species show a spectrum of adaptations
that could be interpreted as representing insectivory (e.g.,
_Cimolestes incisus_,_C. propalaeoryctes_, and _Batadon tenuis_),
perhaps some degree of carnivory upon some larger prey (e.g.,
_Cimolestes magnus), and omnivory or frugivory (e.g., various
species of _Gypsonictops_ and _Purgatorious ceratops_)...(Late
Cretaceous) dental structural differentiation was considerable."
(in _Eutheria_, Kielan-Jaworowska, et al in same volume as
above).
     Within this range of possible diets, egg predation _must_ be
included.  Mammals of today eat eggs, reptiles of the past ate
eggs, birds eat eggs, all God's children eat eggs--I believe the
burden rests with you to say why mammals would _not_ eat eggs.
And, as noted above, this possibility increased toward the K/T.
In past posts I have posited several perfectly reasonable mammal-
eat-dino-eggs scenarios.  No one has complained about them
specifically.  The complaints are of your kind: How, after 100
million of no threat, could mammals become a dino problem.
Simple: things change.  And I have only commented here on
dentition and diet.  Brain capacity, hearing ability, smelling
ability, locomotor ability, social ability, all these things
changed in mammals to their advantage towards the K/T.
     Mammals provided a threat the dinos had never seen before.
They were stealthy, intelligent, aware, capable of exploiting new
diets (with the likely inclusion of dino eggs), and they get
about at night when the dinos could not protect themselves very
well.  Previously, I think the dinos only response to egg
predators was to grow bigger, the better to defend.  But this was
no strategy against the new little mammals.

Birds:  According to Kevin Padian, writing in _Nature_ Vol 382 1
Aug '96,: "...(by the K/T) all but the finishing touches on
flight evolution seem to have been in place."  Birds are
wonderful egg predators.  And, again, inasmuch as they _could_
exploit a resource, either by mobbing a dino nest like sea gulls
or waiting patiently for an opening like crows, they probably
_did_ exploit this resource.  Since they were able fliers they
could strike and escape without penalty.  Just as dinosaurs had
red blood, birds preyed on eggs.  And, since they were more able
at the K/T, they most likely took a higher toll on dinosaurs than
their more clumsy relatives, the enantiornithines (which, I read
on this list, have been found in association with dinosaur
nests!).  Feduccia (_Science_, 267 Feb. 1995) found a small
almost "modern" bird from just before the K/T.  With astounding
arrogance he claims that from this species came all modern birds.
It survived the K/T catastrophe, he says, by cracking crabs on
the shore.  But this is dependency on negative evidence.  A much
more parsimonious claim (and I make it) is that several kinds of
birds had taken advantage of those modern flight characters and
they made it through the K/T.  I believe this is true.  Indeed, I
would think you would have to come up with reasons why it would
_not_ be true.  This claim is admittedly not as strong as the
"red blood" claim but it is stronger than Feduccia's, viz, only
one bird in one niche survived the K/T.  In any case, toward the
K/T, it is parsimonious to say there were more than one species
of modern aspect bird.

     By the way, no one argues that there was a great deal of
original, watershed speciation going on at exactly this time.
Two burgeoning groups, the mammals and the birds, were poised to
take over the world.  They did so using adaptations less profound
than the ones they had just attained: brain power, dentition, and
secure reproduction in mammals; and agile flight and stealthy
reproduction in the birds.  I doubt that these watershed
adaptations were only profound in hind sight.  They most likely
had an impact on all the species of the late Cretaceous.

Ron Orenstein says: "Please explain what dinosaur nesting habits
could possibly have had to do with the extinction of mosasaurs,
enantiornithine birds, belemnites, ammonites, large numbers of
foraminiferan taxa and others at the K/T."

Nothing.  But I'm not sure you can bunch these extinctions
together.  Kevin Padian again in same article as above, says:
"Ironically, like most technological pioneers, the bird groups
that invented these features (i.e., the enantiornithines) were
victims of the success of their progeny, and were replaced by
them before the end of the age of the dinosaurs."  (Padian cites
Chiappe,L. M., _Nature_ 378, 349-355 (1995) for this claim.)
Ammonites are still disputed.  Mosasaurs, I don't know.
     In any case, you are missing my point.  I am not arguing
that there was not an environmental stressor at the K/T, only
that attempts to link it to dinosaur extinction are weak.  How do
_you_ do it?  I have suggested a mechanism.  Dinosaurs under
stress must leave nests unguarded in order to find increasingly
more scarce resources.  This increases nest failure, already
under stress, to extinction-causing levels.  In this scenario,
the reproductive mode is the ultimate cause (since other
reproducers didn't die) and the environmental stress is only the
proximate cause.

Ron Orenstein says:  "Please explain to me why, in a much more
diverse mammalian environment, ratite birds such as emus, rheas
and ostriches manage to survive with "non-stealthy" eggs if a
much less diverse mammalian fauna in the Cretaceous managed to
knock off all of the surviving dinosaurs."

     Funny, but caricature, and ultimately facile.  I have
repeatedly invoked a number of egg predators.  Lizards, cursorial
crocs, and birds have all been found associated with dinosaur
nests.  I have emphasized mammals and birds only because they
seem likely to have posed new threats.  But this must be seen as
predation _on top_ of that already existing from the above and
other dinos.
     Ostriches and emus have a very precarious existence.  Male
emus lay on the nest, fasting for the whole time, in a torpor
(surely this is an adaptation to avoid predator-alerting visits
to and from the nest).  Females maximize their perilous grip on
the future by competing for males.  Ostrich females lay their
eggs in the dominant chick's nest.  They apparently benefit from
her defence.  She arranges their eggs around the outside so
predators take them first!  They both lay in inhospitable places,
where predators are scarce.  Still, you are right, they do
survive.
     The false assumption in your question, i.e., that only
mammals killed off dinosaurs, perhaps gives us a clue to the
riddle of ratite survival.  I think an ostrich would have
suffered much more egg predation if it had lived in the
Cretaceous.  It would have been attacked by big lizards,
cursorial crocs, dinos, and mammals.  Nowadays the threat from
the first three is not as great.  Perhaps, inasmuch as mammals
keep reptile populations in check, they _help_ the ratites to
survive.  I am reminded of David Quammen's account, in _Song of
the Dodo_, of the changes in speciation when Barro Colorado
Island was intentionally inundated: "The curassow and the wood-
quail and the ground cuckoo disappeared from this small patch of
forest--why?--because all their eggs and their nestlings got
eaten--why?--because the coatimundis and their ilk became
extraordinarily numerous--why?--because the pumas and the jaguars
disappeared--why?--because the pumas and the jaguars were
insupportably rare within the small patch of forest and then that
small patch of forest became isolated--why?--because the lake
rose and turned the place into an island.  Insularization was the
first cause, after which extinction cascaded from one trophic
level to another."
I, of course, give _first cause_ award to the strategy of egg-
laying on the ground.  I would argue that the small mammals have
a resiliency to the sort of environmental perturbations seen on
the island.  The ground-layers, on the other hand, are dependent
not only on their own wiles, but on the fate of the top
predators.  If nothing else, the varying strategies _explain_ the
patterns of speciation after the physical event.
     But back to my point which is that just as the birds
depended on the jaguars (because they ate their predators) so
might ratites depend on mammals because may keep down those
species in dry area (for the ostrich and emu at least) which give
them the most problems--lizards.  I don't know about NZ in this,
though, what with no mammals to speak of, or reptiles much
either???

Ron Orenstein says: "How do we know that dinosaurs did not do
exactly that?" (referring to my statement that mammals carry
their babies to safety, and birds hide their eggs on off-shore
islands).  "Is there any reason to assume that the maiasaur "egg
mountains" could not have been on lake sites out of reach of many
egg predators."
     They _were_ out of reach of "many egg predators".   That is
undoubtedly why they went to the trouble to situate their nests
there.  But birds could hide _their_ eggs in even further out-of-
the-way places.  One thinks of migratory swans, geese, penguins
of the antarctic.  These luxuries of stealth were not available
to the egg mountaineers.  And even stay-at-home birds have a much
greater ability to extend their nest-to-foraging-site distance.
All of this means that birds have a greater selection of stealthy
sites than did dinosaurs.  This is a fact.
     As for dinos carrying babies: Are you seriously suggesting
that dinos carried their eggs from safe house to safe house in
order to fool egg predators, perhaps in the dead of night?  If
you mean they carried juveniles, I suppose this is possible.  But
it has nothing to do with my argument which is based on the
treacherous time _before_ hatching as contrasted to the
relatively secure time before birth in a mammal.

Ron Orenstein says he doesn't like my saying that dino
reproduction was unfit.  He says this is "totally misleading and
a trifle arrogant..."  Furthermore, he says: "You have absolutely
no evidence on which to base this statement."

But this is not right.  I have the evidence of my senses to base
it on.  As I walk around this world, in the forests, in the
suburbs, in the cities, on the farms I NEVER SEE A NON-STEALTHY
EGG.  This tells me that the strategy, a strategy big dinosaurs
were stuck with, must not be very fit--otherwise I would see more
of it.  Now, you say that other creatures dominate open-field
niches because of their temperature regimens and/or dentition and
that their placental reproduction has nothing to do with their
success.  I give you reasons why I believe this to be true.  I'll
do it again and add some:
1. Mammals can run away with baby safe inside, whereas dinos must
fight or abandon.  This seems self-evident unless you can provide
Jason Lillegraven and myself with evidence to the contrary.
2. With regard to offspring, mammals have a smaller window of
vulnerability.  For example a wildebeest baby hits the ground
running.  A dinosaur baby must sit relatively exposed until
hatched.
3. The need of dinosaurs to get moving directly after hatching
means potentially helpful developmental programs must be
curtailed to get motor programs up and running (a big dinosaur's
baby would hatch--probably--after about a month or so.  Elephant
baby's develop securely for 10 months [I'm guessing].  This
provides much more ontological flexibility for mammals v. dinos).
This is a fact.
4. Lactation was advantageous.  In Lillegraven's _Repro in
Mesozoic Mammals (see above) lactation is given credit for the
following: "...(it was) important in allowing the delayed
development in young, growing mammals of adult-sized teeth that
are capable of precise occlusal relationships soon after
eruption; ...very rapid post natal growth, particularly of skull
and jaws; early attainment of skeletal and sexual maturity; all
members of a species can specialize upon a narrow range of food
sources or feeding techniques; timing of reproduction can be
partially independent of supply of abundant or specialized foods;
species can persist in impoverished, disturbed or rapidly
changing habitats I give you this argument for survival of
mammals in a catastrophic K/T!); mutualistic social behavior
among adults and sub adults (I paraphrased some of this and not
cited parts).
4. In breeding season dinos must either stay at the nest (using
energy stored in their body--some crocs and emus do this), or
forage near the nest (returning to provision the guard).  Mammals
can range freely, moving at a moment's notice with babies on
board.  Mammal options are more flexible.  This is a fact.

     Now, all of this is not meant as a paean to mammalhood.  I
list the advantages to compare their reproduction with dino's.
Now my argument benefits from an accumulation of circumstantial
evidence, viz., very few non-stealthy egg layers exist;
advantages of stealthy egg laying are patent; open-field niches
are dominated by secure reproducers (mammals); this is at least
in part attributable to their reproductive mode for sound reasons
listed above.  Whether or not it was egg predation that did them
in, their reproductive mode was unfit and would have ultimately
been exposed as such.  Or at least, this is what I believe.  Or
at least, this is a hypothesis I think is worthy of
consideration.

But Ron Orenstein asks me to get into the specifics of dino
reproduction: "How do you know how much physiological effort
dinosaurs invested in their clutches?  Dinosaur eggs are
remarkably small for the size of the adult.  Can you be sure that
dinosaurs did not have the strategy (as some tropical birds
apparently do) of laying small clutches so that if these failed
in the early stages another clutch could be laid with minor
physiological consequences?"

Yes.  They could have layed many small clutches.  But this
doesn't mean it was "inexpensive".  The cost of the egg itself
may well have been infinitesimal, but its defence was not.  And
the strategy you are apparently suggesting for the dinosaurs, of
spraying their eggs all around the country side in the hope that
some of them will hatch, does not seem feasible to me.  Minimal
investment in nest defence may work for a small bird, but a big
dinosaur can be more easily observed by egg predators.  I imagine
that a dinosaur might have a collection of commensal,
mutualistic, and parasitic creatures moving with or next to it
wherever it went.  In any case, a big, observable egg is better
defended than presented to those who would eat it!  Besides, many
dinosaurs layed quite elaborate nests which took much investment
(like megapodes).  Others returned year after year to the same
nest site.  Some dinosaurs were colonial nesters for whom your
excess-egg idea wouldn't work.  Your argument also ignores the
value of nest sites and the substrate in which the eggs are
layed.  Many dinosaurs could _not_ simply lay at will.

     Sorry for the length.  It's late.  I know I haven't
addressed small dinos.