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Re: Mammalian success and egg predation,
[Andrew, I snipped out most of your quoted text since it wasn't
necessary. Everyone, the list has been quiet the past couple of days
through no fault of my own (so far as I know). However, I'm about to
go out of town possibly for as much as a week. I will have access to
e-mail, and I plan to push mail through, but I may do so somewhat
sporadically. I'd hand things to Nedin (and I still might at some
point next week), but the poor bloke should be getting home and
trying to readjust to being upside down again right around now.
Don't want to overload him. -- MR]
At 02:29 PM 6/14/96 -0400, John Bois wrote:
>But big dinosaurs could run smaller dinosaurs off their nests.
>Non-defended nests could be robbed. A cuckoo-style dinosaur could
>parasitize a nest. Predators could get so hungry that the risk of
>leaving fewer genes due to being throttled by a defensive parent was
>smaller than leaving fewer genes by starving to death. And then, it
>is possible that some very new "engineers" came along and attacked the
>dino eggs in a way that they couldn't respond. For they had been
>solving problems of big against big. And the better they got at doing
>that, they must of necessity be less able to deal with small mammalian
>or avian stealthy egg predators.
I am no expert in paleontology or any other field of natural science, and I
don't mean this as an attack on anyone's ideas. However, regarding egg
predation, can we look at some modern day analogies? How many modern
rodents are habitual egg-eaters? For that matter, why haven't all the small
songbirds, who's nests are parasitized by cuckoos, been driven into
extinction. Or, why haven't all the ground-nesting birds,crocodilians,
etc., who's eggs are eaten at every opportunity by nest-robbing monitor
lizards, egg-eating snakes, racoons, opossums, and mustelids (none of which
have gnawing incisors), etc., been driven to extinction? All of these
"victimized" groups are flourishing in areas where they are not in
competition with or hunted by humans. Granted, crocodilians and most birds
defend their nests quite vigorously, but a fair number of eggs still fall
prey to nest-robbers.
To go back to the dinosaurs, is there any fossil evidence that any mammal
preyed upon their eggs on any sort of regular basis? Since the early
mammals were probably opportunistic feeders, it's entirely possible that the
occasional dino nest was raided. However, the eggs of the bigger dinosaurs
were probably as big as the would-be predators -- one egg would have fed
several animals. In my humble, non-expert opinion, it wasn't nest-robbing
that did the dinosraurs in.
Since his is the only "modern" book on the dinosaurs that I've had a chance
to read, I am paraphrasing Dr. Bakker's information in _Dinosaur Heresies_.
I understand that he doesn't sit well with various subscribers to this list.
However, his is the most readily available, readable book. //Please correct
me if I'm wrong. I'd love to read books espousing differing viewpoints.//
He claims that the dinosaurs started to lack in diversity the closer they
got to the K-T boundary. What might have caused that lack of
diversification is beyond me, but the fact is that they (the dinos) were not
replenishing their numbers quick enough to fill all the ecological niches
they once filled. Maybe munching on angiosperm-type plants didn't entirely
agree with the plant-eaters. With a dwindling supply of prey, the
predators' numbers would also have dwindled. I don't know how this chain of
events would have affected the medium- to small-sized dinos, but the
ecological chain was disrupted, and the fur-balls, as Dr. Bakker calls them,
gained their opportunity to step into the unfilled niches. We see that
happening even today, albeit mostly with unwitting human assistance.
European House Sparrows, Starlings, and Rock Doves tend to be more
aggressive than native species and drive them out in areas where they are
introduced. The same thing happened in Hawaii. Most of the native birds
were driven to extinction or very close to it by imported rats, mongooses,
cats, etc. What's to say that the dinosaurs weren't weakened to the point
from which they couldn't fully recover by an as yet undiscovered agent or
collection of agents. That set the stage for the mammals of various types
to step in and start diversifying to fill new niches.
Thanks for allowing me to express my two cents worth.