Re: Hibernating through the K/T?

[John Bois <jbois@umd5.umd.edu>]

On Fri, 17 May 1996, Bill Hunt wrote:

>  With the exception of birds, I believe all of the modern groups
> mentioned above, survived because of some sort of Hibernation/Hunker
> Down and wait it out stratigy.  And Birds have a special ability
> that Dinosaurs don't have: they could Fly!  Doesn't this suggest
> that birds could escape, migrate across mountain ranges, across
> oceans, find a refuge.  Assuming again that they weren't all extinct
> already . . . .  . Dinosaurs were earthbound, stuck, no escape.
> They couldn't migrate fast enough or far enough and they couldn't
> hibernate.  I know I'm painting with a broad brush, but I'm trying
> to understand the big picture...

I agree that hibernation is the best hope for the bolide-is-
sufficient idea of dinosaur extinction.  While it seems to work
for salamanders, lizards, turtles, snakes, frogs, and crocs,
consider the following difficulties with that hypothesis.

1.  Birds survived, as you say.  But to which refugium could they fly
that dinosaurs were excluded.  High latitudes, perhaps.  But we have
found high-latitude dinosaurs?

2. Some dinosaurs may have hibernated.

3. Some modern mammals do hibernate but they fall into the following
two categories: a) bats and other small mammals with extremely high
metabolisms go into daily torpor.  They can't be induced to hibernate
for longer periods.  Mammals of this sort, if they existed in the
Cretaceous, couldn't sleep through any extended "impact winter"; b)
Hibernators that do go into extended periods of dormancy must prepare
for the onset of winter by building fat reserves.  This is used both
as insulation and food.  Animals which don't prepare starve.  As a
fortuitous mechanism for escaping an instant impact winter, this
explanation requires that the mammals were bedding down just as the
bolide struck.  Perhaps, given the different times of onset of winter
at different latitudes, a couple of species were doing this.  But the
distribution of mammal survivorship suggests they represented a
broader spectrum than that of only hibernating species.  For example,
didn't small arboreal primates make it across the K/T?  Yet they are,
today at least, by and large non-hibernators.  Having neither
continuously growing incisors, nor digging claws, they cannot exploit
cold-climate niches and so are generally excluded from places where
hibernation is adaptive!  For here the high quality food is on or
beneath the ground in the form of nuts, and seeds with tough coats.
They are and were ill-adapted for long periods of cold.  Yet they
survived!

        What kind of "just so" story must someone come up with to make
this evidence fit?