[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Predators of the non-stealthy egg theory.

1. Cory Gross says: "...(if dinosaurs went extinct gradually,
mammals should have filled their) niches just as gradually."

I don't think so.  Mammals were small and vulnerable to open-
field attack.  While there were dinosaurs around there could be
no mammals.  While they lived, the dinosaurs (like crocodiles in
the semi-aquatic environment) were niche sovereigns.  They were
so dominant and so well adapted to their niche, they had nothing
to fear from any direct competition.  It's just a shame about
those eggs!  Just as a virus brings down an elephant without
"seeking" to move into its niche, mammals brought down the
dinosaurs (with help from the other egg-predators, of course).

2. Bonnie Blackwell says: "John, you have succumbed to a common
mesozoic myth: namely that mammals just appear in the late

No, Bonnie.  I just believe they became well-adapted for
significant egg-predation towards the end of the Cretaceous. 
They were actually evolving completely independently from the
dinosaurs for most of the Mesozoic.  Or, if they interacted at
all, they probably evolved in response TO THE DINOSAURS PREYING
ON THEM.  In this sense they were living in a separate habitat. 
At some point they evolved critical adaptations--something as
unspectacular as the enhanced ability to learn, for example,
could have profound and completely uncounterable consequences for
the dinosaurs.
But your feelings echo what many believe.  Indeed, it is Nick
Pharris' main point:  "I maintain that the situation of the
dinosaurs vs. egg predators remained _status quo_ throughout the
Mesozoic.  I see no evidence that the...mammals, and birds at the
K/T boundary suddenly became much better at eating non-avian
dinosaur eggs."
     But there _is_ much evidence of change, especially in
mammals.  Cognitive development is quantifiable (cranial
capacity).  This newly evolved "technology" could allow the
mammal to learn new predatory tactics.  For example, they could
now imagine a group of eggs which were out of site, under a pile
of leaves (incidentally, my 7 yr old daughter's science project
involves egg-predation and crows.  She, is piling wood chips and
leaves on top of an egg which she puts out each day.  Today the
crows rummaged through a one foot pile to reach the egg.  To them
she is the Great Benefactor).  Compare the mammals enlightened
attitude to reality to that of the Grey Lag Goose.  This animal,
if it sees one of its eggs roll out its nest, will carry out the
following fixed-action pattern: waddle up to the egg, roll it
back with the beak until it reaches the nest, and sit on the
reunited clutch.  Evil researchers, experimenting on the goose's
cognitive powers, roll out an egg.  The goose moves out of its
nest, begins to roll the egg back.  But then the egg is taken. 
What does the goose do?  Attack the researcher! you say.  No, it
continues to roll thin air back to its nest, and it continues
until the whole pattern is complete.  With brains like these, it
is no wonder (assuming they had cognitive abilities somewhat in
common, that they couldn't cope with the new mammals wiz kids. 
But this is just one of the possible new developments.  One may
consider quantifiable auditory, an locomotor developments (I
think)--advances in burrowing techniques, again, developed in the
crucible of intense predation, may have, BY ITSELF, been a
functional branch point--something for which the dinosaurs had no
answer.  Imagine a city of mammals predators living RIGHT IN THE
CENTER OF YOUR COLONIAL EGG BED, just five feet beneath the
surface--what do you, the T-Rex do when, every night they come
creeping out, with their little alert eyes glinting in the shine
of yours egg's shells?

4. Thomas Holtz says: "...the fact of avian survival reflects
that this small part of the dino genome survived the extinction. 
Making a taxon paraphyletic in order to wipe it out is not fair
in extinction studies."

However you want to classify it is alright with me.  But what
happened was this: non-stealthy egg-laying, non-avian dinosaurs
became extinct, and stealthy egg-laying avian dinosaurs did not.

5. Thomas Holtz says: "Why would a...small hypsilophodont nest be
so hard to conceal."

Because even they were above the threshhold of discovery.  A bird
approaches its nest, alights near it, looks for predators, and
finally, flies to its nest.  A hypsilophodont could not do this. 
If it were to brave the deep close cover required for absolute
protection of the egg, it must deal with the alert, and
reproductively secure mammals on their own terms--especially when
they left the nest--which must be often!

6. T. H. says: "...there is no evidence that Mesozoic birds were
tree nesters."

But we would expect to it.

7. "(mammal egg-layers had problems too, but they made it through
the K/T)."

Mammal egg layers could be stealthy.  They could put them in
burrows.  Look at the platypus.  It burrows _under water_.  Tell
me that is not an adaptation for stealth--against egg predation!

8. "(Cretaceous birds were incapable of attacking juvenile

Poor fossil record--unknown.  It is likely that prey birds ate
then what they eat now: small animals.  If juvenile dinosaurs
were too big for birds, there were plenty of other animals to
prey on them.  Greg Paul says that most of the biomass of
dinosaurs is tied up in the juveniles, i.e., they get eaten
before they mature.  I maintain that dinosaur existence had been
marginal for a long time.  This perhaps contributed to the slow
decline in diversity (if that's what the fossil record says) over
the Cretaceous).  Then, something happened to push them quietly
into a precipitous decline (in geologic time), i.e., more dinos
were dying than were being born.  A very small difference in
predation could have achieved this.

9. Darren Naish says: "...funny how (New Zealand's dinosaurs)
died out at the same time as other forms worldwide."

A conundrum!  But, if NZ broke off with a representative cargo of
dinos and mammals (is that what happened?), would it not be
reasonable to suggest that mammals could evolve to exploit the
same niche dimension as the mainland mammals (eggs), in a process
which had perhaps already begun.  Surely the recent introduction
of mammals has mimicked what has happened on the mainland:
extinction of small, two-legged, non-flying, ground laying

10. Norm King says: "There's no (impact scenario dogma.  But I'm
still sitting here waiting here for an equally competent

Well, it _was_ your challenge which drew me out.  If nothing else
it was good to get it off my chest.  But I wonder what sort of
evidence along these lines would convince you that the reason
dinosaurs died out was over predation of their eggs and

11. N.K. says: "We might expect to see _something_ to fill
(dinosaur) niches (if they died out gradually)."

See comment 1. to Cory Gross.

12. Stan Friesen says: "(cooling, vulcanism, etc., etc.,)combined
together to produce the extensive extinctions found at the K/T

This "no one cause" alternative is very attractive because, 1.
Things often occur in just this way, eg., the Russian Revolution.
2. Living systems are, we know, unfathomably complex. 3. It
absolves us from looking for a single cause in this complexity.
But it ignores what in this case _is_ a very simple pattern:
stealthy egg layers, non-egg layers, and niche sovereigns
survived the K/T, while non-stealthy egg-layers did not.

13. Jeffrey Martz says: "(John Bois' likening of mammals invading
NZ, to mammals preying on dinosaur eggs is) not fair."

It is fair.  And I will argue this in a subsequent post called
"The novel invasion of dinosaurs by mammals".